(199
4). I
n P. Bertelson, P. Eelen, G. d'
Yde
wal
le (
Eds
.International Perspectives on Psychological Scienc~
Volume 1: Le
adin
g Jh
emes
. Erl
baum
: Hill
sdal
e, NJ.
The
Int
erac
tion
of N
atur
e an
dN
urtu
re in
Dev
elop
men
t:A
Par
alle
l Dis
trib
uted
Processing Perspective
Jam
es L
. McC
lella
ndD
epar
tmen
t of P
sych
olog
y, C
arne
gie
Mel
lon
Uni
vers
ity,
Pitt
sbur
gh, U
SA
Para
llel d
istr
ibut
ed p
roce
ssin
g (P
DP)
mod
els
prov
ide
a ri
ch s
et o
f re
sour
ces
for
expl
orin
g is
sues
of
natu
re, n
urtu
re a
nd th
eir
inte
ract
ion
in c
ogni
tion
deve
lopm
ent.
I pr
esen
t the
ess
entia
l asp
ects
of
the PDP(orconnectionist) framework, and I draw
para
llels
bet
wee
n th
e ch
ild a
s le
arne
r an
d th
e m
echa
nism
s of
lear
ning
inco
nnec
tioni
st s
yste
ms.
The
rem
aini
ng s
ectio
ns d
iscu
ss s
ome
of th
e im
plic
atio
nsof
this
fra
mew
ork
for
our
unde
rsta
ndin
g of
the
acqu
isiti
on o
f kn
owle
dge.
I p
oint
outlh
at m
any
lines
ofa
rgum
enllh
al h
ave
typi
cally
bee
n gi
ven
in s
uppo
rt o
fnal
ivis
tap
proa
ches
nee
d to
be
reco
nsid
ered
in th
e lig
ht o
f th
e ch
arac
teri
stic
s of
PD
P m
odel
sof
lear
ning
and
dev
elop
men
t. T
he f
irst
of
thes
e se
ctio
ns p
oint
s ou
t tha
t con
nect
ioni
stm
odel
s of
fer
a dr
amat
ic a
dvan
ce o
ver
clas
sica
l ass
ocia
tioni
st a
ppro
ache
s to
lear
ning
. The
sec
ond
illus
trat
es h
ow s
tage
- lik
e pr
ogre
ssio
ns c
an b
e un
ders
tood
inte
rms
of th
e ty
pica
l lea
rnin
g tr
ajec
tori
es s
een
in c
onne
ctio
nist
mod
els.
The
thir
dse
ctio
n co
nsid
ers
the
mea
ning
and
pos
sibl
e so
urce
s of
ear
ly c
ompe
tenc
e fr
om-
aPD
P pe
rspe
ctiv
e, a
nd th
e fo
urth
con
side
rs h
ow c
onne
ctio
nist
mod
els
may
she
d lig
hton
the
fact
that
som
e of
the
stru
ctur
e of
hum
an b
ehav
iour
app
ears
to b
e im
pose
dby
the
lear
ner.
In
all,
the
chap
ter
amou
nts
to a
n ar
gum
ent t
hat c
onne
ctio
nist
mod
els
allo
w u
s to
see
way
s in
whi
ch e
xper
ienc
e m
ight
lead
to th
e ri
ch a
nd in
tere
stin
gco
gniti
ve s
truc
ture
s an
d de
velo
pmen
tal p
rogr
essi
ons
that
hav
e of
ten
been
take
n as
supp
ortiv
e of
nat
ivis
t app
roac
hes.
INT
RO
DU
CT
ION
Whe
re d
o co
gniti
ve a
bilit
ies
com
e fr
om?
Are
they
bor
n in
us,
inna
te e
ndow
men
tsof
nat
ure?
Are
they
pro
duct
s of
exp
erie
nce.
pla
in a
nd s
impl
e? O
r do
they
ari
sethrough the interaction of the characteristics of the or
gani
sm a
nd th
e
McC
LE
LL
AN
D4. NATURE AND NURTURE
IN D
EV
EL
OPM
EN
T
envi
ronm
ent?
The
se q
uest
ions
hav
e st
ood
at th
e ce
ntre
of
the
stud
y of
min
d fo
rce
ntur
ies.
Som
e of
the
mos
t pro
min
ent r
esea
rche
rs o
f ou
r ce
ntur
y-C
hom
sky,
Skinner and Piaget-ha
ve ta
ken
each
of
thes
e vi
ews,
and
eac
h ha
s sp
awne
d la
rge
follo
win
gs w
ithin
psy
chol
ogy
and
the
larg
er s
cien
tific
com
mun
ity~
Whi
ch p
ositi
on is
rig
ht?
The
pur
e em
piri
cist
trad
ition
no
long
e~ h
olds
muc
hsw
ay; a
nd th
ere
is c
erta
inly
a v
ery
activ
e m
ovem
ent i
n th
e fi
eld
toda
y th
at f
avou
rsth
e na
tivis
t pos
ition
. Yet
I th
ink
ther
e is
a f
eelin
g in
man
y qu
aner
s th
at e
xper
ienc
em
ust p
laya
larg
er r
ole than the mere setting of parameters in an otherwise
inna
tely
pre
dete
nnin
ed c
ogni
tive
syst
em.
In th
is c
hapt
er, I
will
add
ress
this
que
stio
n. I
will
arg
ue f
or a
n in
tera
ctio
nist
posi
tion
, sim
ilar
in s
ome
way
s to
Pia
get's
. My
mai
n ai
m, t
houg
h, "
Viii
not
be
tochampion interactionism
per se.
Rat
her,
it w
ill b
e to
sug
gest
that
the
para
llel
dist
ribu
ted
proc
essi
ng f
ram
ewor
k (a
ka th
e co
nnec
tioni
st f
ram
ewor
k) h
as b
road
impl
icat
ions
for
our
und
erst
andi
ng o
f co
gniti
ve d
evel
opm
ent.
Thi
s fr
amew
ork,
I w
ill a
rgue
, pro
vide
s m
echa
nism
s an
d id
eas
that
allo
w u
s to
exp
lore
the
inte
rpla
yof
nat
ure
and
nunu
re, a
nd th
at s
ugge
st h
ow e
xper
ienc
e m
ay b
e th
e en
gine
that
driv
es d
evel
opm
ent,
thro
ugh
chan
nels
sha
ped
by b
oth
inna
te c
onst
rain
ts a
nd th
est
ruct
ure
of th
e en
viro
nmen
t.I
begi
n w
ith a
pre
sent
atio
n of
the
esse
ntia
l asp
ects
of
para
llel d
istr
ibut
edpr
oces
sing
that
are
rel
evan
t to
the
poin
ts I
hope
to m
ake
abou
t cog
nitiv
ede
velo
pmen
t , a
nd I
dra
w p
aral
lels
bet
wee
n th
e ch
ild a
s le
arne
r/ex
peri
ence
r an
dth
e m
echa
nism
s of
lear
ning
in c
onne
ctio
nist
sys
tem
s. T
he r
emai
ning
sec
tions
disc
uss
som
e of
the
impl
icat
ions
of
this
fra
mew
ork
for
our
unde
rsta
ndin
g of
the
repr
esen
tatio
n an
d ac
quis
ition
of
know
ledg
e.Fi
rst,
I w
ill p
oint
out
that
con
nect
ioni
st m
odel
s of
fer
a dr
amat
ic a
dvan
ce o
ver
othe
r fo
nns
of le
arni
ng, p
anic
ular
ly c
lass
ical
ass
ocia
tioni
st a
ppro
ache
s. T
his
poin
tis
cru
cial
, sin
ce it
rel
ates
qui
te s
tron
gly
to th
e qu
estio
n of
wha
t is
lear
nabl
e.Se
cond
, I w
ill e
xplo
re th
e tim
e-co
urse
of
deve
lopm
ent.
In p
artic
ular
, I w
illco
nsid
er s
tage
- lik
e pr
ogre
ssio
ns. H
ere
I w
ill d
emon
stra
te h
ow c
onne
ctio
nist
mod
els
impl
emen
t mec
hani
sms
of c
ogni
tive
chan
ge v
ery
clos
e to
som
e of
the
mec
hani
sms
prop
osed
by
Piag
et, a
nd h
ow th
ey c
an a
ddre
ss s
ome
of th
e pu
zzle
sth
at h
ave
plag
ued
othe
r ex
perie
ntia
l acc
ount
s of
the
sour
ces
of p
rogr
ess
from
stag
e to
sta
ge. T
hird
, I w
ill c
onsi
der
the
mea
ning
and
pos
sibl
e so
urce
s of
ear
lyco
mpe
tenc
e , f
rom
a c
onne
ctio
nist
poi
nt o
f vi
ew. F
inal
ly, I
will
con
side
r ho
wco
nnec
tioni
st m
odel
s m
ay s
hed
light
on
the
fact
that
som
e of
the
stru
ctur
e of
hum
an b
ehav
iour
app
ears
to b
e im
pose
d by
the
lear
ner.
A f
ew o
f th
e po
ints
mad
e in
the
chap
ter
have
bee
n m
ade
prev
ious
ly in
McC
lella
nd (
1989
). B
ates
and
Elm
an (
1993
), K
arm
iloff-
Smith
(19
92a,
I 992
b) a
nd P
lunk
ett a
nd S
inha
(19
91)
have
writ
ten
on r
elat
ed to
pics
and
man
yof
thei
r ar
gum
ents
hav
e co
ntri
bute
d to
the evolution of the viewpoints
expr
esse
d he
re.
TH
E P
DP
FR
AM
EW
OR
K
Para
llel d
istr
ibut
ed p
roce
ssin
g (P
DP)
pro
vide
s us
with
a f
ram
ewor
k fo
r th
inki
ngab
out t
he m
echa
nism
s th
at r
epre
sent
, acq
uire
and
use
kno
wle
dge.
The
fra
mew
ork
is d
escr
ibed
in d
etai
l in
the
firs
t fou
r ch
apte
rs o
f R
umel
han,
McC
lella
nd a
nd th
ePD
P R
esea
rch
Gro
up (
1986
c). H
ere
I to
uch
only
on
poin
ts r
elev
ant t
o th
e pr
esen
tdi
scus
sion
.Fi
rst,
PDP
assu
mes
that
cog
nitiv
e pr
oces
ses
aris
e fr
om th
e in
tera
ctio
ns o
f la
rge
num
bers
of
sim
ple
proc
essi
ng u
nits
, org
anis
ed in
to m
odul
es. A
ver
y ge
neri
cex
ampl
e of
suc
h a
netw
ork
is s
how
n in
Fig
. 4. 1
. With
in e
ach
mod
ule,
eac
h un
itco
mpu
tes
a si
mpl
e fu
nctio
n of
the
inpu
ts it
rec
eive
s fr
om o
ther
uni
ts. C
ruci
al to
us w
ill b
e th
e fa
ct th
at th
is is
a c
ontin
uous
but
non
- lin
ear
func
tion,
like
the
one
show
n in
Fig
. 4,1
. Sec
ond,
the
PDP
appr
oach
ass
umes
that
the
know
ledg
e th
atgo
vern
s pr
oces
sing
is s
tore
d in
the
stre
ngth
s of
the
conn
ectio
ns a
mon
g th
e un
its.
Such
kno
wle
dge
allo
ws
the
patte
rn p
rese
nt o
n on
e se
t of
units
to g
ive
rise
to o
ther
patte
rns
on o
ther
set
s of
uni
ts; o
r fo
r th
e pa
ttern
of
activ
atio
n at
one
poi
nt in
tim
eto
giv
e ri
se to
a s
ucce
ssor
at t
he n
ext m
omen
t. T
hird
, the
PD
P ap
proa
ch a
ssum
esth
at a
cqui
sitio
n of
kno
wle
dge
occu
rs th
roug
h th
e ad
just
men
t of
conn
ectio
nst
reng
ths.
The
se a
djus
tmen
ts, i
n tu
rn, a
re d
rive
n by
sig
nals
ari
sing
ulti
mat
ely
from
exte
rnal
inpu
ts to
the
netw
ork.
I d
iscu
ss th
is a
spec
t mor
e fu
lly b
elow
.
The
Rol
e of
the
Inna
te E
ndow
men
t
Let
us
now
con
side
r ho
w th
is f
ram
ewor
k al
low
s us
to e
xplo
re th
e in
tera
ctio
n of
inna
te e
ndow
men
t and
exp
erie
nce
as d
eten
nina
nts
of th
e co
urse
and
out
com
e of
know
ledg
e ac
quis
ition
. The
inna
te e
ndow
men
t has
sev
eral
asp
ects
. Am
ong
them
is th
e gr
oss
arch
itect
ure
of th
e sy
stem
- the
mod
ules
, the
num
ber
of p
roce
ssin
gun
its in
eac
h, a
nd th
eir
initi
al c
onne
ctiv
ity (
Rum
elha
n, H
into
n, &
McC
lella
nd,
;..,:: -0(
Inpu
t
FIG
. 4. 1 A
gene
ric
conn
eciio
nisl
nel
wor
k, lo
gelh
er w
ilh il
s ac
lival
ion
func
lion.
McC
LE
LL
AN
D4. NATURE AND NURTURE
IN D
EV
EL
OPM
EN
T
1986
a). W
e kn
ow o
f co
urse
that
the
brai
n is
not
at a
ll fu
lly c
onne
cted
and
the
orga
nisa
tion
of th
is c
onne
ctiv
ity d
eten
nine
s w
hich
uni
ts w
ill b
e in
line
to r
ecei
vere
lativ
ely
dire
ct a
udito
ry in
put,
whi
ch to
rec
eive
vis
ual i
nput
, whi
ch to
com
bine
thes
e tw
o so
urce
s of
info
nnat
ion,
and
so
on.
A s
econ
d as
pect
of
the
inna
te e
ndow
men
t con
cern
s th
e ba
sic
rule
s th
at g
over
nth
e pr
opag
atio
n of
act
ivat
ion
and
the
adju
stm
ent o
f co
nnec
tion
stre
ngth
s. T
hese
rule
s, to
the
exte
nt th
at th
ey d
iffe
r in
dif
fere
nt p
arts
of
the
syst
em, p
rovi
de a
mea
nsw
here
by m
odal
ity-
or d
omai
n-sp
ecifi
c co
nstr
aint
s ca
n be
impo
sed
on th
eco
gniti
ve s
yste
m. T
o th
e ex
tent
that
they
are
gen
eral
thro
ugho
ut th
e sy
stem
, the
ypr
ovid
e a
set o
f pe
rvas
ive
com
mon
mec
hani
sms
for
proc
essi
ng a
nd le
arni
ng,
A th
ird
aspe
ct o
f th
e in
nate
end
owm
ent c
once
rns
the
deta
iled
para
met
ers
ofdi
ffer
ent p
arts
of
the
syst
em. E
ven
whe
n th
e ba
sic
rule
s of
pro
cess
ing
and
conn
ectio
n st
reng
th a
re h
eld
cons
tant
, dif
fere
nces
in p
aram
eter
s ca
n le
ad to
mec
hani
sms
with
ver
y di
ffer
ent c
hara
cter
istic
s. A
s on
e ex
ampl
e, O
'Rei
lly (
1992
)to
ok a
net
wor
k (i
llust
rate
d in
Fig
. 4.2
) co
nsis
ting
of tw
o se
ts o
f in
tern
al u
nits
,ea
ch r
ecei
ving
inpu
t fro
m th
e sa
me
set o
f in
puts
, and
eac
h se
ndin
g ou
tput
to a
llof
the
outp
ut u
nits
. The
inte
rnal
uni
ts in
the
two
pool
s di
ffer
ed o
nly
in th
e ra
teat
whi
ch th
eir
activ
atio
ns c
hang
ed o
ver
time.
Tho
se o
n th
e le
ft c
hang
ed a
ctiv
atio
nsl
owly
whe
n th
eir
inpu
ts c
hang
ed, w
hile
thos
e on
the
righ
t cha
nged
thei
rac
tivat
ion
very
rap
idly
in r
espo
nse
to c
hang
ing
inpu
ts. T
he n
etw
ork
was
ask
ed
to p
erfo
nn th
e ta
sk o
f lea
rnin
g to
indi
cate
the
loca
tion
and
iden
tity
of in
put
patte
rns.
Som
e of
the
outp
ut u
nits
wer
e us
ed to
spe
cify
iden
tity,
and
the
othe
rsw
ere
used
to s
peci
fy s
hape
, with
bot
h se
ts o
f hi
dden
uni
ts c
onne
cted
to a
ll of
the
outp
ut u
nits
. Eac
h in
put p
atte
rn a
rose
at a
dis
cret
e po
int i
n tim
e an
d th
en p
ersi
sted
for
seve
ral t
ime
step
s, m
ovin
g ab
out f
rom
pla
ce to
pla
ce w
ithin
the
inpu
t arr
ay,
as if
the
netw
ork
wer
e re
ceiv
ing
inpu
t at d
iffe
rent
ret
inal
loca
tions
ove
r a
seri
esof
eye
fix
atio
ns. T
hus,
the
iden
tity
of a
pat
tern
tend
ed to
per
sist
for
sev
eral
tim
est
eps,
whi
le th
e lo
catio
n of
the
patte
rn m
oved
aro
und.
The
res
ult w
as th
at th
epo
ol o
f un
its w
ith th
e sl
ow r
ate
of c
hang
e be
cam
e sp
ecia
lised
for
det
ectin
g th
eid
entit
y of
the
obje
ct, w
hile
the
units
with
the
fast
er r
ate
of c
hang
e be
cam
esp
ecia
lised
for
det
ectin
g its
loca
tion.
Thi
s is
but
one
exa
mpl
e of
a b
urge
onin
gbo
dy o
f w
ork
show
ing
how
mod
ules
with
slig
htly
dif
fere
nt in
itial
par
amet
ers
orbi
ases
can
bec
ome
diff
eren
tially
spe
cial
ised
thro
ugh
expe
rien
ce. T
his
part
icul
arca
se a
lso
emph
asis
es th
e jo
int r
oles
of
envi
ronm
ent a
nd in
nate
str
uctu
re. I
t is
the
com
bina
tion
of th
e fa
ct th
at o
bjec
t ide
ntity
rem
ains
the
sam
e as
the
retin
allo
catio
n ch
ange
s w
ith th
e fa
ct th
at th
e un
its in
dif
fere
nt m
odul
es d
iffe
r in
thei
rte
mpo
ral p
aram
eter
s th
at d
eten
nine
s th
e ou
tcom
e in
this
cas
e.
The
Rol
e of
Exp
erie
nce
Now
let u
s fo
cus
on th
e ro
le o
f ex
peri
ence
. Her
e I
will
beg
in b
y pr
opos
ing
age
nera
l way
of
thin
king
abo
ut h
ow e
xper
ienc
e m
ight
pro
pel c
ogni
tive
deve
lopm
ent,
and
then
I w
ill r
elat
e th
is id
ea b
ack
to p
aral
lel d
istr
ibut
edpr
oces
sing
(M
cCle
lland
, 198
9). W
e be
gin
by th
inki
ng o
f th
e ch
ild e
xper
ienc
ing
an e
nvir
onm
ent i
nvol
ving
an
ongo
ing
sequ
ence
of
even
ts. W
e as
sum
e th
at th
echild, while alert and attending, is always making implicit predictions
for
wha
tm
ight
hap
pen
next
. Let
me
emph
asis
e th
e im
plic
it na
ture
of
the
proc
ess.
I d
onm
ean
that
the
child
is c
onsc
ious
ly a
war
e of
ask
ing,
and
pos
ing
answ
ers
to th
equ
estio
n
, "
Wha
ts
com
ing
next
? W
hat
s co
min
g ne
xt?"
I d
o m
ean,
thou
gh, t
hat
his
or h
er c
ogni
tive
syst
em is
in f
act a
ntic
ipat
ing
the
futu
re, a
nd th
at a
rea
ctio
nca
n oc
cur
if th
ese
expe
ctat
ions
are
vio
late
d, B
ehav
iour
ally
, suc
h re
actio
ns a
reac
com
pani
ed b
y or
ient
ing
resp
onse
s--e
ye m
ovem
ents
, pup
il di
latio
n, in
crea
ses
in g
aze
dura
tion,
etc
. The
y al
so, a
t lea
st in
lang
uage
pro
cess
ing,
gen
erat
e la
rge
and
robu
st e
voke
d po
tent
ials
, suc
h as
the
N40
0 of
Kut
as a
nd H
illya
rd (
1980
).N
ote
that
mat
chin
g or
mis
mat
chin
g is
alw
ays
a m
atte
r of
deg
ree
in P
OP
syst
ems-
it is
a m
atte
r of
the
cons
iste
ncy
betw
een
one
patte
rn o
f ac
tivat
ion
and
anot
her-
and
in g
ener
al a
ctua
l eve
nts
will
alw
ays
diff
er to
som
e de
gree
fro
mw
hat i
s an
ticip
ated
.In
any
cas
e, a
s ev
ents
occ
ur, t
hey
perm
it th
e ch
ild to
com
pare
impl
icit
pred
ictio
ns w
ith w
hat a
ctua
lly h
appe
ns n
ext ,
and
ther
eby
to le
arn
to m
ake
bette
rpr
edic
tions
fo
r th
e fu
ture
. The
ess
entia
l ass
umpt
ion
is th
at th
e ch
ild u
ses
the
follo
win
g pr
oced
ure
to a
djus
t the
pre
dict
ions
:
Inpu
t
FIG
. 4.2 O'
Rei
llys network. The slow units in the module
on
the
lefl
bec
ome
"wha
t" u
nits
and
the fast units in the module
on
the
righ
t bec
ome
"whe
re"
units
.
4. NATURE AND NURTURE
IN D
EV
EL
OPM
EN
TM
cCL
EL
LA
ND
Adj
ust e
ach
para
met
er o
f th
e m
ind
in p
ropo
rtio
n to
the
exte
nt th
at it
s ad
just
men
tw
ill r
educ
e th
e di
scre
panc
y be
twee
n pr
edic
ted
and
obse
rved
eve
nts.
Seco
nd, t
he k
now
ledg
e is
inhe
rent
ly g
rade
d in
nat
ure.
Thi
s is
a m
ost i
mpo
rtan
tpo
int,
and
one
that
will
per
vade
muc
h of
the
rest
of
this
cha
pter
. Whe
n a
netw
ork
is f
irst
pla
ced
in a
n en
viro
nmen
t, its
con
nect
ion
wei
ghts
mig
ht b
e in
itial
ised
tosm
all,
rand
om v
alue
s, w
ithin
bro
ad c
onne
ctiv
ity c
onst
rain
ts. I
ts p
redi
ctio
ns,
then
, mig
ht b
e in
itial
ly w
eak
and
rand
om. A
s ex
peri
ence
s oc
cur ,
pre
dict
ions
grad
ually
bec
ome
attu
ned
to s
ituat
ions
, and
aft
er m
ore
and
mor
e tim
e ha
s pa
ssed
,th
e ne
twor
k be
com
es s
truc
ture
d in
acc
orda
nce
with
the
cont
ents
of
the
dom
ain.
At f
irst
we
wou
ld s
ay th
e ne
twor
k kn
ows
noth
ing,
and
at t
he e
nd w
e w
ould
say
the
netw
ork
know
s th
e st
ruct
ure
of th
e do
mai
n, b
ut in
the
mid
dle
our
ordi
nary
tenn
inol
ogy
and
way
s of
thin
king
abo
ut w
hat i
t mea
ns to
"kn
ow"
som
ethi
ng b
reak
dow
n. T
he n
etw
ork
has
a ki
nd o
f pa
rtia
l kno
wle
dge-
it ge
nera
tes
pred
ictio
nsth
at in
clin
e to
war
ds b
eing
cor
rect
, or
are
corr
ect o
nly
in c
erta
in c
ases
, or
that
capt
ure
the
gros
s re
gula
ritie
s w
ithou
t cap
turi
ng th
e su
btle
r de
tails
. The
pro
cess
is c
ompl
etel
y gr
adua
l and
ther
e is
no
spec
ial d
iscr
ete
poin
t at w
hich
we
wou
ldsa
y th
e ne
twor
k no
w k
now
s, a
nd b
efor
e th
is, i
t did
not
kno
w.
Thi
rd, a
cqui
sitio
n is
gra
dual
and
incr
emen
tal.
Gra
dual
ness
is im
port
ant,
asw
e w
ill s
ee in
our
con
side
ratio
n of
an
exam
ple
belo
w, b
ecau
se it
allo
ws
the
over
all
dire
ctio
n of
cha
nge
to b
e de
tenn
ined
by
the
over
all s
truc
ture
in th
e do
mai
n th
atit
is le
arni
ng r
athe
r th
an s
peci
fic
indi
vidu
al s
timul
i. It
is in
crem
enta
l, in
that
eac
hch
ange
bui
lds
on e
arlie
r ch
ange
s. A
s in
Pia
get's
dev
elop
men
tal t
heor
y, w
here
cogn
itive
str
uctu
re e
mer
ges
from
acc
omm
odat
ion
and
assi
mila
tion,
eac
h ne
wad
apta
tion
is b
ut a
slig
ht v
aria
tion
and
exte
nsio
n of
the
syst
em th
at r
esul
ted
from
prev
ious
act
s of
ada
ptat
ion
(see
Fla
vell,
196
3, f
or d
iscu
ssio
n).
Giv
en th
e im
plic
it na
ture
of
the
know
ledg
e em
bodi
ed in
PO
P sy
stem
s, it
may
seem
to m
any
rese
arch
ers
at f
irst
gla
nce
that
PO
P sy
stem
s ha
ve r
elat
ivel
y lit
tleto
off
er a
ny e
ffor
t to
unde
rsta
nd c
ogni
tive
deve
lopm
ent.
Thi
s w
ill b
e es
peci
ally
true
for
res
earc
hers
who
thin
k of
"re
al"
know
ledg
e as
exp
licit
know
ledg
e, o
rw
ho th
ink
of d
isco
ntin
uous
cha
nge,
suc
h as
insi
ght,
as th
e ha
llmar
k de
velo
pmen
t. T
here
is c
erta
inly
no
deny
ing
that
exp
licit
know
ledg
e ex
ists
. or
that
the
deve
lopm
ent o
f ex
plic
it kn
owle
dge
is a
maj
or a
spec
t of
cogn
itive
deve
lopm
ent.
But
I b
elie
ve th
at im
plic
it kn
owle
dge,
of
the
kind
that
is b
uilt
into
conn
ectio
nist
sys
tem
s th
roug
h ex
perie
nce,
is m
ore
fund
amen
tal ,
in th
at it
stru
ctur
es th
e ve
ry r
epre
sent
atio
ns o
f ex
peri
ence
itse
lf th
at p
rovi
de th
e in
put t
oex
plic
it th
ough
t pro
cess
es. C
erta
inly
, we
all a
ppre
ciat
e fr
om li
ngui
stic
s th
esu
btle
ty th
at im
plic
it kn
owle
dge
can
have
, and
the
role
that
it c
an p
lay
in s
hapi
ngou
r re
pres
enta
tions
of
lingu
istic
stim
uli.
I sh
are
the
view
of
Kar
milo
ff- S
mith
(199
2a)
that
suc
h im
plic
it kn
owle
dge
is a
s im
port
ant i
n ot
her
dom
ains
, and
serv
es, a
s it
does
for
lang
uage
, as
the
subs
trat
e on
whi
ch e
xplic
it co
gniti
on is
ultim
atel
y bu
ilt. O
n th
is v
iew
, our
und
erst
andi
ng o
f ex
plic
it co
gniti
on w
ill b
een
rich
ed b
y a
deep
er u
nder
stan
ding
of
this
sub
stra
te, T
here
fore
, the
res
t of
this
chap
ter
will
foc
us o
n th
e im
plic
atio
ns o
f PO
P fo
r th
inki
ng a
bout
the
natu
re a
ndac
quis
ition
of
know
ledg
e of
this
impl
icit
kind
.
The
mos
t str
aigh
tfor
war
d an
d ty
pica
l way
of
rela
ting
this
idea
to c
onne
ctio
nist
netw
orks
is a
s fo
llow
s (s
ee, e
.g. E
lman
, 199
0): F
irst,
we
imag
ine
that
the
inpu
tto
the
syst
em r
epre
sent
s th
e cu
rren
t situ
atio
n, f
rom
whi
ch a
pre
dict
ion
will
be
mad
e. T
his
inpu
t may
be
sign
als
aris
ing
from
out
side
the
syst
em, o
r th
e sy
stem
own
inte
rnal
sta
te. S
econ
d, w
e im
agin
e th
at th
e ou
tput
rep
rese
nts
the
pred
ictio
nth
at th
e sy
stem
mak
es f
or w
hat m
ay h
appe
n ne
xt. F
inal
ly, w
e im
agin
e th
at th
eac
tual
nex
t eve
nt a
rise
s as
a p
atte
rn o
f ac
tivity
on
thes
e un
its. T
he r
ule
for
lear
ning
bec
omes
:
Adj
ust e
ach
conn
ectio
n w
eigh
t in
the
netw
ork
in p
ropo
rtio
n to
the
exte
nt th
atits
adj
ustm
ent w
ill r
educ
e th
e di
ffer
ence
bet
wee
n th
e ou
tput
of
the
netw
ork
and
the
actu
al n
ext e
vent
.
The
alg
orith
m s
tand
ardl
y us
ed f
or a
djus
ting
conn
ectio
n st
reng
ths,
the
back
-pr
opag
atio
n le
arni
ng a
lgor
ithm
(R
umel
hart
, Hin
ton
, & W
illia
ms,
198
6b),
issimply an algorithm for calculating the relevant quantities-in
par
ticul
ar, t
heex
tent
to w
hich
an
adju
stm
ent t
o ea
ch w
eigh
t will
red
uce
a m
easu
re o
f th
edi
ffer
ence
s ac
ross
the
outp
ut u
nits
.G
iven
suc
h a
lear
ning
rul
e, e
xper
ienc
e dr
ives
cha
nges
in c
onne
ctio
n w
eigh
ts,
ther
eby
caus
ing
the
netw
ork
to le
arn
how
to r
epre
sent
and
use
inpu
ts to
mak
ebe
tter
pred
ictio
ns f
or th
e fu
ture
. Jus
t thi
s ap
proa
ch h
as b
een
used
to tr
ain
netw
orks
to d
o a
num
ber
of v
ery
impo
rtan
t and
inte
rest
ing
thin
gs, w
hich
we
will
turn
toin
a m
omen
t. F
or n
ow, t
houg
h, I
wan
t to
high
light
bri
efly
thre
e ke
y fe
atur
es o
fth
e co
nnec
tioni
st a
ppro
ach
to k
now
ledg
e an
d kn
owle
dge
acqu
isiti
on. -
Pro
pert
ies
of C
onne
ctio
nist
Kno
wle
dge
Firs
t, th
e kn
owle
dge
is im
plic
it, in
the
very
sen
se th
at th
is te
nn h
as b
een
used
in th
e de
velo
pmen
tal l
itera
ture
by
Kan
nilo
ff-Smith (1986,
1991
, 199
2a),
and
inth
e m
emor
y lit
erat
ure
by a
num
ber
of in
vest
igat
ors
(see
Sch
acte
r, 1
987)
. It i
skn
owle
dge
that
is e
mbe
dded
in s
peci
fic
proc
essi
ng m
echa
nism
s. I
t is
know
ledg
eth
at c
an b
e us
ed to
mak
e pr
edic
tions
, perceptual anticipations and pattern
com
plet
ions
, and
to s
ubse
rve
the
grad
ual a
cqui
sitio
n of
dom
ain-
spec
ific
ski
lls.
Vio
latio
ns o
f pr
edic
tions
mad
e on
the
basi
s of
suc
h kn
owle
dge
can
serv
e as
the
basi
s of
mak
ing
vari
ous
kind
s of
judg
emen
ts, a
s w
hen
a pe
rson
is a
sked
to m
ake
a ju
dgem
ent a
bout
the
gram
mat
ical
ity o
f a
pote
ntia
l exa
mpl
e of
a n
atur
al o
rar
tific
ial l
angu
age
(Kno
wlto
n, R
amus
, & S
quir
e, 1
992;
Reb
er, 1
976,
198
9). B
utth
e kn
owle
dge
itsel
f is
not
dir
ectly
ava
ilabl
e as
suc
h, e
ither
for
rep
ort,
for
expl
icit
reas
onin
g, o
r an
y ot
her
purp
ose.
McC
LE
LL
AN
D4. NATURE AND NURTURE
IN D
EV
EL
OPM
EN
T
IMPL
ICA
TIO
NS
OF
TH
E P
DP
APP
RO
AC
HA
lthou
gh h
e ac
know
ledg
es th
at e
xper
ienc
e pl
ays
a ro
le in
thes
e de
velo
pmen
ts,
Kei
l arg
ues
in s
ever
al p
lace
s (1
981,
198
7, 1991 a, 1991 b) for the idea that the
abili
ty to
use
exp
erie
nce
in th
e se
rvic
e of
the
cons
truc
tion
of s
uch
rela
tiona
lsystems of meaning depends on the use of
a priori,
dom
ain-
spec
ific
kno
wle
dge.
As
pan
of h
is a
rgum
ent h
e po
ints
out
a c
halle
nge
for
any
lear
ning
- bas
ed a
ccou
ntthat does not rely on such
a priori
know
ledg
e. H
e ar
gues
that
cla
ssic
alas
soci
atio
nist
acc
ount
s-ac
coun
ts h
e ta
kes
as p
arad
igm
atic
of
expe
rien
ce-b
ased
appr
oach
es to
kno
wle
dge
acqu
isiti
on-a
ppea
r to
lack
the
cruc
ial a
bilit
y to
shi
ftfr
om a
rel
ianc
e on
mer
ely
corr
elat
ed f
eatu
res
to a
rel
ianc
e on
dee
per
rela
tiona
lpr
open
ies.
The
rea
sons
for
this
, he
argu
es, l
ie in
the
basi
s on
whi
ch th
e le
arni
ngm
echa
nism
s pr
ovid
ed b
y su
ch a
ccou
nts
lear
n an
d us
e w
hat t
hey
have
lear
ned,
Kei
l (19
91a)
not
es tw
o ke
y pr
oper
ties
of a
ssoc
iatio
nist
acc
ount
s: le
arni
ng o
ccur
sby
con
tigui
ty (
for
exam
ple,
con
tigui
ty o
f a
situ
atio
n w
ith a
n ou
tcom
e, o
r of
acu
rren
t eve
nt w
ith th
e ne
xt e
vent
) an
d ge
nera
lisat
ion
occu
rs b
y si
mila
rity,
perm
ittin
g re
spon
ding
to n
ovel
inpu
ts b
ecau
se o
f th
eir
sim
ilari
ty to
fam
iliar
case
s, T
hus,
for
exa
mpl
e, I
ass
ocia
te th
e si
ght o
f a
rose
with
the
smel
l of
a ro
seby
con
tigui
ty, l
earn
ing
to p
redi
ct th
e sm
ell f
rom
the
visu
al a
ppea
ranc
e. I
kno
wth
at a
noth
er r
ose
will
sm
ell a
s sw
eet b
ecau
se it
look
s si
mila
r to
the
firs
t ros
e,In essence, K
eil's
arg
umen
t is
that
chi
ldre
n-an
d ce
rtai
nly adults-do not
alw
ays
gene
ralis
e on
the
basi
s of
sim
ilari
ty. R
athe
r, th
ey c
ome
to r
ely,
som
etim
esal
mos
t exc
lusi
vely
, on
deep
er, r
elat
iona
l inf
orm
atio
n. L
acki
ng a
n ex
peri
ence
- bas
edal
tern
ativ
e to
ass
ocia
tioni
sm th
at o
verc
omes
this
lim
itatio
n, h
e po
ints
to th
e w
ork
of S
pelk
e an
d ot
hers
(e.
g. S
pelk
e, 1
991;
Spe
lke,
Bre
inlin
ger,
Mac
ombe
r, &
Jaco
bson
, 199
2) f
or e
vide
nce
of v
ery
earl
y (a
nd th
eref
ore
puta
tivel
y in
nate
)kn
owle
dge
in a
num
ber
of d
omai
ns, a
nd h
e su
gges
ts th
at c
hild
ren
may
hav
e a
hand
ful o
f in
nate
"pr
oto-
theo
ries
" th
at a
llow
them
to d
eter
min
e ju
st w
hat t
heap
prop
riat
e ba
ses
are
or g
ener
alis
atio
n, in
eac
h of
sev
eral
dom
ains
,N
ow le
t us
take
a lo
ok a
t thi
s ar
gum
ent,
in li
ght o
f PD
P m
odel
s, a
nd s
ee h
owit
hold
s up
. At f
irst
gla
nce,
it s
eem
s th
at P
DP
mod
els
may
not
cha
nge
thin
gs m
uch,
sinc
e th
ese
mod
els
do le
arn
from
con
tigui
ty o
f si
tuat
ions
and
out
com
es, a
s I
have
alre
ady
expl
aine
d. F
unhe
rmor
e, it
is a
lso
true
that
they
tend
to g
ener
alis
e by
sim
ilari
ty: s
imila
r pa
ttern
s of
act
ivat
ion
on o
ne la
yer
of u
nits
tend
to p
rodu
cesi
mila
r pa
ttern
s of
act
ivat
ion
at th
e ne
xt. T
his
may
be
why
so
man
y co
gniti
vesc
ient
ists
and
phi
loso
pher
s w
ith o
ther
wis
e w
idel
y di
verg
ent v
iew
s es
sent
ially
dism
iss
conn
ectio
nist
mod
els
of le
arni
ng. P
utna
m h
as s
tate
d, f
or e
xam
ple,
that
thin
gs th
at c
anno
t be
expr
esse
d in
term
s of
cor
rela
tions
bet
wee
n ha
rd-c
oded
vari
able
s ca
nnot
be
foun
d by
the
algo
rith
m, a
nd a
re n
ot a
ble
to r
ecov
er th
est
ruct
ure
that
lies
beh
ind
the
surf
ace.
Fod
or h
as s
tate
d, "
The
que
stio
n is
whe
ther
you
can
get s
ome
succ
ess
that
you
cou
ld n
ot g
et b
y ju
st d
oing
sta
tistic
s. .
I th
ink
of th
em (
c onn
ectio
nist
mod
els)
as
anal
og s
tatis
tics
pack
ages
,I
The
quo
tatio
ns f
rom
Fod
or a
nd P
utna
m h
ave
been
use
d w
ith p
erm
issi
on o
f th
e au
thor
s (p
erso
nal
com
mun
icat
ion,
199
2). T
he s
tate
men
ts w
ere
orig
inal
ly m
ade
in in
terv
iew
s w
ith P
. Bau
mga
nner
,w
ho c
onve
yed
thes
e qu
otat
ions
to m
e fo
r co
mm
ent.
My
mai
n po
int i
n th
is c
hapt
er is
to s
how
that
the
PDP
appr
oach
has
pro
foun
dim
plic
atio
ns f
or o
ur u
nder
stan
ding
of
deve
lopm
ent.
In g
ener
al, m
y ar
gum
ent i
sth
at w
ith th
e to
ols
prov
ided
by
the
PDP
fram
ewor
k w
e ca
n ca
ll in
to q
uest
ion
som
e of
the
tene
ts o
f na
tivis
t app
roac
hes
on th
e on
e ha
nd, a
nd b
reat
he n
ew li
fein
to th
e in
tera
ctio
nist
pos
ition
on
the
othe
r.T
he r
est o
f th
is c
hapt
er w
ill p
ursu
e th
is p
oint
thro
ugh
four
spe
cifi
c ar
gum
ents
.Fi
rst,
I w
ill s
how
that
con
nect
ioni
st le
arni
ng r
ules
allo
w u
s to
ext
end
the
scop
eof
wha
t is
lear
nabl
e fa
r be
yond
wha
t was
thou
ght p
ossi
ble
unde
r ea
rlier
appr
oach
es, t
here
by r
educ
ing
the
need
man
y au
thor
s ha
ve s
een
to b
uild
spe
cifi
ckn
owle
dge
in f
rom
the
star
t. Se
cond
, I w
ill a
rgue
that
PD
P al
low
s us
to u
nder
stan
dst
age-
like
prog
ress
ions
in d
evel
opm
ent m
ore
clea
rly
than
was
pos
sibl
e un
der
Piag
et's
inte
ract
ioni
st a
ccou
nt. T
hird
, I w
ill p
oint
out
how
PD
Ppro
vide
s us
with
a la
ngua
ge in
whi
ch to
ret
hink
the
mea
ning
of m
any
of th
e in
tere
stin
g ph
enom
ena
of e
arly
com
pete
nce
in in
fant
s, F
ourt
h, I
will
sug
gest
how
PD
P al
low
s us
toun
ders
tand
how
a le
arni
ng p
roce
ss m
ay s
truc
ture
the
dom
ain
that
is b
eing
lear
ned.
The
cha
pter
doe
s no
t lay
out i
ts o
wn
deta
iled
theo
ry o
f de
velo
pmen
t, no
r do
esit
even
use
the
PDP
appr
oach
to m
ake
spec
ific
pre
dict
ions
. Rat
her,
it u
ses
exam
ple
sim
ulat
ions
to d
emon
stra
te s
peci
fic
poin
ts th
at c
ontr
ast w
ith v
iew
poin
ts o
ften
take
n in
mor
e na
tivis
t app
roac
hes.
Tak
en to
geth
er, t
he e
xam
ples
sup
port
the
mor
ege
nera
l cla
im th
at P
DP
can
lead
us
to r
ethi
nk m
uch
of th
e ev
iden
ce th
at h
as b
een
take
n in
sup
port
of
the
view
that
muc
h es
sent
ial c
onte
nt k
now
ledg
e is
inna
te a
ndth
at e
xper
ienc
e pl
ays
only
an
elab
orat
ing
or p
aram
eter
-set
ting
role
in d
evel
opm
ent.
Ext
endi
ng th
e D
omai
n of
the
Lea
rnab
leIn
ord
er to
bri
ng o
ut th
e w
ay in
whi
ch c
onne
ctio
nist
lear
ning
allo
ws
us to
ext
end
the
dom
ain
of th
e le
arna
ble,
and
to u
nder
scor
e its
rel
evan
ce to
bas
ic q
uest
ions
abou
t the
sou
rces
of
our
conc
eptu
al k
now
ledg
e, I
will
foc
us o
n an
exa
mpl
e us
edby
Kei
l (19
87)
in h
is r
esea
rch
on c
once
ptua
l dev
elop
men
t. K
eil c
onsi
ders
how
child
ren
com
e to
shi
ft th
eir
cate
gori
satio
n be
havi
our
from
an
earl
y re
lianc
e on
an e
nsem
ble
of c
hara
cter
istic
fea
ture
s to
a la
ter
relia
nce
on c
ore
rela
tiona
lpr
oper
ties.
Am
ong
the
exam
ples
he
uses
is th
e us
e of
kin
ship
term
s su
ch a
sun
cle
. He
repo
rts
that
chi
ldre
n sh
ift f
rom
an
initi
al a
ccep
tanc
e of
des
crip
tions
such
as
"a f
ello
w w
ho w
as n
ot r
elat
ed to
any
one
in y
our
fam
ily b
ut w
as a
big
pal o
f you
r da
d's
and
brou
ght y
ou p
rese
nts
on y
our
birt
hday
and
Chr
istm
as"
toa
will
ingn
ess
to a
ccep
t des
crip
tions
suc
h as
"a
two
year
old
who
was
you
r m
ombr
othe
r. K
eil s
tres
ses
that
the
deve
lopm
enta
l pat
tern
indi
cate
s th
at th
e ch
ild'
conc
eptu
al d
evel
opm
ent r
efle
cts
the
emer
genc
e or
a "r
elat
iona
l sys
tem
" re
leva
ntto
the
spec
ific
dom
ain
of k
now
ledg
e, r
athe
r th
an p
iece
mea
l acq
uisi
tion
ofkn
owle
dge
abou
t, sa
y, u
ncle
s bu
t not
aun
ts, o
r an
y ki
nd o
f do
mai
n ge
nera
lch
ange
in o
vera
ll ap
proa
ch,
McC
LE
LL
AN
D4. NATURE AND NURTURE
IN D
EV
EL
OPM
EN
T
But
ther
e is
som
ethi
ng v
ery
wro
ng w
ith a
ll th
ese
argu
men
ts. A
lthou
ghco
nnec
tioni
st m
odel
s ar
e si
mila
r in
som
e w
ays
to a
ssoc
iatio
nist
mod
els,
and
alth
ough
they
are
ext
ensi
ons
of e
xist
ing
stat
istic
al te
chni
ques
, the
re is
a c
ruci
aldi
ffer
ence
. In
conn
ectio
nist
mod
els,
the
very
bas
is o
f de
term
inin
g w
hat i
s si
mila
rto
wha
t is
part
of
wha
t is
disc
over
ed in
the
cour
se o
f le
arni
ng. T
his
is n
ot ju
st a
mat
ter
of e
mph
asis
ing
som
e di
men
sion
s an
d de
-em
phas
isin
g ot
hers
(al
thou
ghthis is what happens in some cases), but of
tota
lly r
ecod
ing
each
inpu
t so
as to
map
it in
to a
sim
ilari
ty s
pace
who
se s
truc
ture
depe
nds,
not on the surface
properties of the inputs, but
on th
e de
man
ds th
at a
re m
ade
by th
e la
sk o
fpredicting outcomesfrom inputs.
Thi
s se
nsiti
vity
of
the
inte
rnal
rep
rese
ntat
ions
to th
e ta
sk th
ey a
re r
equi
red
to p
erfo
rm d
ram
atic
ally
incr
ease
s th
e ra
nge
of w
hat
such
mod
els
are
able
to a
chie
ve c
ompa
red
to a
ssoc
iatio
nist
mod
els
or s
tand
ard
stat
istic
al te
chni
ques
.T
his
poin
t has
bee
n ill
ustr
ated
man
y tim
es in
con
nect
ioni
st le
arni
ng r
esea
rch.
The
impo
rtan
ce o
f co
nstr
uctin
g re
pres
enta
tions
was
the
them
e of
Rum
elha
rt e
tal
. (I9
86b)
and
alm
ost e
very
inte
rest
ing
appl
icat
ion
of c
onne
ctio
nist
lear
ning
sinc
e th
eir
pape
r ha
s m
ade
esse
ntia
lly th
is p
oint
. The
exa
mpl
e I
have
cho
sen
tous
e he
re is
one
of
the
firs
t to
dem
onst
rate
this
poi
nt, b
y H
into
n (1
986)
. It h
appe
nsto
use
an
exam
ple
that
rel
ates
spe
cifi
cally
to K
eil's
kin
ship
exa
mpl
es, a
s is
ther
efor
e pa
rtic
ular
ly a
ppro
pria
te. I
spe
nd s
ome
time
revi
ewin
g th
is e
xam
ple
here
beca
use
its p
oint
app
ears
to h
ave
been
lost
on
man
y ve
ry im
port
ant r
esea
rche
rsan
d co
mm
enta
tors
.H
into
n tr
aine
d a
conn
ectio
nist
net
wor
k to
ans
wer
que
stio
ns a
bout
the
kins
hip
rela
tions
am
ong
two
grou
ps o
f in
divi
dual
s, o
ne c
alle
d E
nglis
h an
d th
e ot
her
calle
dIt
alia
n (F
ig. 4
.3).
With
in e
ach
grou
p, th
ere
wer
e pa
ralle
l set
s of
kin
ship
rel
atio
ns,
but t
here
wer
e no
rel
atio
ns b
etw
een
the
grou
ps. H
into
n tr
aine
d a
conn
ectio
nist
netw
ork
on th
e re
latio
ns a
mon
g th
ese
indi
vidu
als
in th
e fo
llow
ing
way
. The
task
of th
e ne
twor
k w
as to
take
que
ries
that
can
be
glos
sed
"Per
sonl
' s R
elat
ion
is" (e.
g. "
Col
ins Uncle is -
) an
d to
then
res
pond
with
the
corr
ect
com
plet
ion
or c
ompl
etio
ns o
f th
e pr
opos
ition
(Pe
rson
2). A
s sh
own
in F
ig. 4
.4he
set
up
two
pool
s of
inpu
t uni
ts, o
ne c
onsi
stin
g of
a u
nit f
or e
ach
poss
ible
filt
erof
the
Pers
on I
rol
e, a
nd th
e ot
her
cons
istin
g of
a u
nit f
or e
ach
of th
e ki
nshi
pre
latio
ns. T
his
allo
wed
him
' to
pres
ent q
uerie
s by
sim
ply
activ
atin
g th
eap
prop
riat
e Pe
rson
I u
nit a
nd th
e ap
prop
riat
e R
elat
ion
unit.
He
also
set
up
a se
tof
out
put u
nits
, for
Per
son2
, aga
in c
onsi
stin
g of
one
uni
t for
eac
h pe
rson
, to
allo
wth
e ne
twor
k to
act
ivat
e a
unit
corr
espo
ndin
g to
the
indi
vidu
al o
r in
divi
dual
s at
the
othe
r en
d of
the
rela
tion.
In
betw
een
ther
e w
ere
sepa
rate
gro
ups
of h
idde
nun
its, o
ne f
or th
e ne
twor
k to
use
for
an
inte
rnal
representation of PI, one to
repr
esen
t the
rel
atio
n, o
ne to
rep
rese
nt th
e co
mbi
natio
n of
P I
and
the
rela
tion
and
one
to r
epre
sent
P2.
The
impo
rtan
t poi
nt is
that
, at t
he in
put a
nd o
utpu
t lev
els,
the
pers
ons
and
the
rela
tions
are
eac
h re
pres
ente
d by
dis
tinct
inpu
t uni
ts. I
nitia
lly. t
he c
onne
ctio
nsfr
om th
e in
put u
nits
to th
e co
rres
pond
ing
repr
esen
tatio
n un
its a
re r
ando
m, s
o
Chr
isto
pher
= P
enel
ope
And
rew
= C
hris
tine
Margaret = Arthur V
icto
ria =
Jam
es Je
nnif
er =
Cha
rles
Col
inC
harl
otte
Rob
erto
= M
arla
Pie
rro
= F
ranc
esca
Gina = Emilio Lu
cia
= M
arco
Ang
ela
= T
omas
o
Alf
onso
Soph
ia
FIG
. 4.
The
fam
ily tr
ees
unde
rlyi
ng th
e tr
aini
ng c
orpu
s us
ed b
y H
into
n (J
989
). T
he s
ymbo
l "m
eans
"married 10
. From
Para
llel D
istr
ibut
ed P
roce
ssin
g: I
mpl
icat
ions
for
psy
chol
ogy
and
neur
obio
logy
(p
. 49)
, by
R,
M. M
orri
s. N
ew Y
ork:
Oxf
ord
Uni
vers
ily P
ress
. Cop
yrig
ht 1
989
M. M
orri
s. R
epro
duce
d by
pen
niss
ion.
Pers
on2
Person 1
Rel
atio
n
FIG
.4 The
netw
ork
used
by
Hin
ton
(198
6) to
lear
n th
e fa
mily
tree
s sh
own
in F
ig, 4
. 3. R
epro
duce
dby
pen
niss
ion.
that
the
sim
ilari
ty r
elat
ions
am
ong
the
initi
al in
tern
al r
epre
sent
atio
ns a
re a
rbitr
ary
and
unre
late
d to
the
task
. Dur
ing
the
cour
se o
f tr
aini
ng, t
he c
onne
ctio
n w
eigh
tsth
roug
hout
the
netw
ork
chan
ge. O
n ea
ch tr
aini
ng tr
ial,
the
netw
ork
uses
its
4. NATURE AND NURTURE
IN D
EV
EL
OPM
EN
TM
cCL
EL
LA
ND
exis
ting
conn
ectio
n w
eigh
ts to
pre
dict
the
corr
ect c
ompl
etio
n or
com
plet
ions
;th
e ou
tput
is c
ompa
red
to th
e co
rrec
t res
pons
e; a
nd th
e co
nnec
tions
are
adj
uste
dto
red
uce
the
diff
eren
ce u
sing
bac
k-pr
opag
atio
n, T
he w
eigh
ts f
rom
the
Pers
on I
inpu
t uni
ts to
the
Pers
on I
rep
rese
ntat
ion
units
det
erm
ine
how
eac
h pe
rson
isre
pres
ente
d. T
he r
epre
sent
atio
ns c
aptu
re w
hat m
ight
be
calle
d a
theo
ry o
f th
eun
derl
ying
str
uctu
re b
ehin
d th
e se
t of
spec
ific
pro
posi
tions
on
whi
ch th
e ne
twor
kw
as tr
aine
d. T
hey
repr
esen
t as
sim
ilar
thos
e in
divi
dual
s w
ho p
lay
sim
ilar
role
s,w
ithin
and
acr
oss
the
two
fam
ily tr
ees
show
n in
Fig
. 4.
We
can
try
to v
isua
lise
the
disc
over
ed s
imila
rity
str
uctu
re2
by im
agin
ing
the
patte
rns
of a
ctiv
atio
n on
thes
e pe
rson
-rep
rese
ntat
ion
units
as
poin
ts in
a s
ix-
dim
ensi
onal
spa
ce (
whe
re e
ach
dim
ensi
on c
orre
spon
ds to
the
activ
atio
n of
one
of th
e si
x un
its).
Sin
ce s
uch
spac
es a
re d
iffi
cult
to v
isua
lise.
and
sin
ce u
nits
inthe network tend to be used redundantly anyway, w
e ca
n us
e pr
inci
pal
com
pone
nts
anal
ysis
to p
ick
out t
he im
port
ant d
imen
sion
s. W
hen
we
do th
is, w
efi
nd th
at th
ere
are
thre
e st
rong
com
pone
nts.
We
can
then
plo
t the
indi
vidu
als
ina
thre
e-di
men
sion
al s
pace
, rep
rese
ntin
g w
here
eac
h in
divi
dual
fal
ls w
ith r
espe
ctto
eac
h of
thes
e th
ree
com
pone
nts.
The
thre
e-di
men
sion
al s
truc
ture
is s
till
som
ewha
t dif
ficu
lt to
gra
sp in
the
proj
ecte
d vi
ew p
rese
nted
in F
ig, 4
.5, b
ut it
can
be b
roug
ht o
ut b
y us
ing
the
fact
that
the
repr
esen
tatio
ns o
f th
e in
divi
dual
s
can
be s
epar
ated
per
fect
ly b
y a
plan
e th
roug
h th
e sp
ace
show
n in
Fig
. 4. 5
that
leav
es a
ll of
the
Ital
ians
on
one
side
of
the
plan
e, a
nd a
ll of
the
Eng
lish
on th
eot
her.
The
dim
ensi
on p
erpe
ndic
ular
to th
is p
lane
can
be
calle
d th
e " n
atio
nalit
ydi
men
sion
. The
net
wor
k di
scov
ers
this
dim
ensi
on b
ecau
se it
pla
ys a
ver
y st
rong
role
in r
estr
ictin
g th
e po
ssib
le c
ompl
etio
ns o
f a
quer
y, s
ince
Per
son
I an
d Pe
rson
2al
way
s ha
ve th
e sa
me
natio
nalit
y.W
e ca
n th
en lo
ok a
t the
pro
ject
ion
of th
e E
nglis
h an
d th
e It
alia
n gr
oups
ont
oth
e se
para
ting
plan
e, a
nd w
hat w
e se
e is
sho
wn
in F
ig. 4
. 6. F
or b
oth
the
Eng
lish
and
the
Ital
ians
, the
old
er g
ener
atio
n (s
quar
es)
is a
t the
top
of th
e pl
ane ,
the
youn
ger
gene
ratio
n (X
' s)
at th
e bo
ttom
, and
the
mid
dle
gene
ratio
n (t
rian
gles
) is
in b
etw
een.
Als
o, f
or b
oth
the
Eng
lish
and
Ital
ians
, the
indi
vidu
als
in th
e le
ftbr
anch
es o
f th
e tr
ees
show
n in
Fig
. 4. 3
(op
en s
ymbo
ls)
are
loca
ted
to th
e le
ft o
fth
e pl
ane,
and
the
indi
vidu
als
in th
e ri
ght b
ranc
hes
in F
ig. 4
.3 (
fille
d sy
mbo
ls)
are
loca
ted
to th
e ri
ght.
In g
ener
al, w
ithin
gen
erat
ions
, cor
resp
ondi
ng in
divi
dual
s
Eng
lish
Fam
ily T
ree
Rec
over
ed
0 0
Italia
n' .
English' +
+ +
(It
Ital
ian
Fam
ily T
ree
Rec
over
ed
-0.
-0.
-0.
-0.
-O.
-0.
-0.
-0,
-0.
.... 0 0
(QI
FIG
. 4.
The
inte
rnal
rep
rese
ntat
ions
of
the
indi
vidu
als
in th
e tw
o fa
mily
tree
s, d
ispl
ayed
as
poin
ts in
a m
ullid
imen
sion
al s
pace
.
FIG
.P
roje
ctio
ns o
f the
rep
rese
ntat
ions
sho
wn
in F
ig. 4
, 5 o
nto
the
plan
e th
at s
epar
ates
the
Eng
lish
from
the
lIal
ians
. See
text
for
exp
lana
tion.
, The
pal
lern
s us
ed f
or th
e an
alys
is d
iscu
ssed
in th
is a
nd th
e fo
llow
ing
para
grap
hs w
ere
kind
lysu
pplie
d by
Geo
ff H
into
n. w
ho r
e-ra
n th
e ne
twor
k de
scri
bed
in h
is 1
986
pape
r to
reg
ener
ate
the
data
.
McC
LE
LL
AN
D4. NATURE AND NURTURE
IN D
EV
EL
OPM
EN
T
in th
e tw
o tr
ees
occu
py c
orre
spon
ding
loca
tions
, with
onl
y sl
ight
dif
fere
nces
betw
een
the
posi
tion
of e
ach
Eng
lish
and
the
corr
espo
ndin
g It
alia
n.T
he p
oint
of
revi
ewin
g th
is d
emon
stra
tion
is to
mak
e cl
ear
that
the
netw
ork
has
lear
ned
to tr
eat a
s si
mila
r, b
oth
with
in a
nd b
etw
een
the
two
fam
ily tr
ees,
thos
ein
divi
dual
s w
ho o
ccup
y th
e m
ost s
imila
r po
sitio
ns in
eac
h tr
ee. T
he r
easo
nin
divi
dual
s at
sim
iliar
loca
tions
in th
e tr
ee a
re g
iven
sim
ilar
repr
esen
tatio
ns is
that
thes
e re
pres
enta
tions
are
use
ful f
or a
llow
ing
the
netw
ork
to s
olve
the
prob
lem
pose
d by
the
quer
y-co
mpl
etio
n ta
sk, s
ince
the
com
plet
ions
of
prop
ositi
ons
invo
lvin
gin
divi
dual
s lo
cate
d at
sim
ilar
plac
es in
the
fam
ily tr
ees
occu
py s
imila
r tr
ee p
ositi
ons.
Giv
en th
e us
e of
this
bas
is f
or a
ssig
ning
sim
ilari
ty to
the
Pers
on I
inpu
ts, t
hene
twor
k ca
n gc
..ner
alis
e pr
oper
ly to
cas
es th
at w
ere
not p
rese
nted
in tr
aini
ng. I
nth
is c
ase,
eig
ht o
f th
e re
latio
ns w
ere
held
bac
k fr
om th
e tr
aini
ng c
orpu
s an
d on
lyap
pear
ed d
urin
g te
stin
g. T
he n
etw
ork
used
the
repr
esen
tatio
ns it
had
der
ived
for
each
indi
vidu
al d
urin
g th
e co
urse
of
trai
ning
to g
ener
alis
e pr
oper
ly a
t the
tim
eof
test
. It w
as a
ble
to d
o th
is in
a v
ery
sim
ple
way
. The
nat
iona
lity
dim
ensi
on o
fth
e re
pres
enta
tion
of P
erso
n I
dete
rmin
ed th
e na
tiona
lity
of th
e re
spon
se te
rm.
Oth
erw
ise,
the
repr
esen
tatio
ns o
f co
rres
pond
ing
indi
vidu
als
in th
e di
ffer
ent
fam
ily tr
ees
wer
e id
entic
al. T
here
fore
, wha
t it l
earn
ed a
bout
an
indi
vidu
al in
one
tree
tran
sfer
red
to in
divi
dual
s in
the
othe
r.In
sho
rt, t
he n
etw
ork
lear
ns b
y co
ntig
uity
and
gen
eral
ises
by
sim
ilari
ty, b
ut it
diff
ers
in a
cru
cial
res
pect
fro
m a
ssoc
iatio
nist
mod
els
and
stan
dard
sta
tistic
alte
chni
ques
. Unl
ike
thes
e m
echa
nism
s, it
ass
igns
the
sim
ilari
ty r
elat
ions
am
ong
the
patte
rns
as p
art o
f w
hat i
t lea
rns
thro
ugh
the
use
of a
sim
ple
grad
ual a
ndin
crem
enta
l pro
cedu
re fo
r ad
just
ing
the
stre
ngth
s of
the
conn
ectio
ns a
mon
g un
its.
One
of
the
key
feat
ures
of
wha
t hap
pens
in th
e process of assigning
repr
esen
tatio
ns is
the
crea
tion
of c
ateg
orie
s-gr
oups
of p
atte
rns
cont
aini
ngsi
mila
r m
embe
rs-a
nd d
istin
ctiv
e fe
atur
es th
at d
iffe
rent
iate
mem
bers
of
diff
eren
tca
tego
ries
. As
in th
e fa
mily
tree
s ex
ampl
e, s
uch
cate
gori
es s
uppo
rt g
ener
alis
atio
n.E
lman
(19
90)
cons
ider
ed th
is is
sue
as it
rel
ates
to s
ynta
x an
d S
t. Jo
hn a
ndM
cCle
lland
(19
90; M
cCle
lland
, St.
John
, & T
arab
an, 1
989)
con
side
red
this
mat
ter
in a
con
nect
ioni
st m
odel
of
sent
ence
com
preh
ensi
on. H
uman
lang
uage
user
s ca
n pa
rse
unfa
mili
ar b
ut g
ram
mat
ical
sen
tenc
es b
ecau
se th
ey k
now
the
cate
gori
es a
nd s
ubca
tego
ries
' of n
ouns
and
ver
bs. S
o ca
n co
nnec
tioni
st n
etw
orks
that
dis
cove
r th
ese
cate
gori
es th
roug
h gr
adua
l lea
rnin
g. I
n th
e St
. Joh
n an
dM
cCle
lland
cas
e, a
s in
Hin
ton
s ne
twor
k, it
is th
e di
scov
ered
sim
ilari
ty s
truc
ture
,ba
sed
on th
e ro
les
each
wor
d pl
ays
in c
onst
rain
ing
the
inte
rpre
tatio
n of
the
mea
ning
of
vari
ous
sent
ence
s, th
at g
over
ns g
ener
alis
atio
n, r
athe
r th
an a
ny s
urfa
cesi
mila
rity
am
ong
part
icul
ar in
put p
atte
rns.
The
fac
t the
con
nect
ioni
st m
odel
s di
scov
er th
eir
own
inte
rnal
rep
rese
ntat
ions
,an
d th
e fa
ct th
at th
ese
repr
esen
tatio
ns c
an s
erve
as
a pr
inci
pled
bas
is f
or n
on-t
rivi
alge
nera
lisat
ions
, app
ears
to h
ave
been
igno
red
in d
iscu
ssio
ns, s
uch
as th
e on
e by
Keil (l99Ia), where the point is
to m
otiv
ate
a na
tivis
t app
roac
h by
app
ealin
g to
the insufficiency of experience-ba
sed
appr
oach
es. T
he f
act t
hat a
ssoc
iatio
nist
mod
els,
and
not
con
nect
ioni
st m
odel
s, a
re d
iscu
ssed
by
Kei
l , s
impl
y in
dica
tes
that
the
thin
king
und
erly
ing
nativ
ist a
ppro
ache
s is
bas
ed in
par
t on
an in
suff
icie
ntap
prec
iatio
n of
the
pow
er o
f w
hat c
an b
e ac
com
plis
hed
by th
e ne
wer
and
mor
epo
wer
ful m
echa
nism
s of
lear
ning
that
are
ava
ilabl
e in
the
conn
ectio
nist
fra
mew
ork.
I ha
ve c
hose
n to
foc
us o
n K
eil's
pre
sent
atio
n of
thes
e is
sues
bec
ause
of
his
clar
ity in
layi
ng h
is p
ositi
on o
ut a
nd b
ecau
se o
f th
e sp
ecif
ic r
elev
ance
of
Hin
ton
dem
onst
ratio
n to
his
ana
lysi
s of
the
acqu
isiti
on o
f ki
nshi
p kn
owle
dge.
But
the
poin
t is
a ve
ry g
ener
al o
ne, a
nd I
bel
ieve
that
ther
e ha
s be
en a
fai
lure
in th
e w
ork
of o
ther
key
aut
hors
(am
ong
them
Fod
or a
nd P
utna
m)
to a
ttend
to th
e di
ffer
ence
sbe
twee
n co
nnec
tioni
st le
arni
ng m
echa
nism
s an
d pr
e-ex
istin
g id
eas
such
as
asso
ciat
ioni
st m
odel
s or
sta
ndar
d st
atis
tical
tech
niqu
es. T
his
is u
nfor
tuna
te o
ntw
o gr
ound
s. O
ne is
the
poin
t alr
eady
mad
e , th
at c
onne
ctio
nist
mod
els
are
far
mor
e po
wer
ful t
han
asso
ciat
ioni
st m
odel
s or
sta
ndar
d st
atis
tical
tech
niqu
es. T
heot
her
is th
at th
e us
e of
con
nect
ioni
st m
odel
s do
es n
ot e
ntai
l the
cla
im o
ften
attributed to associationists that the organism starts as a
tabula rasa
with
not
hing
mor
e th
an d
omai
n-in
depe
nden
t pri
ncip
les
to g
uide
it. O
n th
e co
ntra
ry, a
s I
have
alre
ady
indi
cate
d, it
is q
uite
eas
y to
inco
rpor
ate
dom
ain-
spec
ific
var
iatio
n. T
his
allows an exploration of the full range of possibilities, ranging from pure
tabu
lara
sa
formulations, to strongly pr
e-st
ruct
ured
acc
ount
s. T
he a
ppea
l of
conn
ectio
nist
mod
els
is n
ot th
at th
ey c
omm
it th
e re
sear
cher
to o
ne f
orm
ulat
ion
or th
e ot
her ,
but
that
they
pro
vide
the
oppo
rtun
ity to
exp
lore
a w
ide
rang
e of
poss
ible
acc
ount
s of
the
role
s of
nat
ure
and
nurt
ure
in d
evel
opm
ent.
Whi
le it
seem
s to
me
we
can
take
the
Hin
ton
wor
k as
rai
sing
que
stio
ns a
bout
the
need
for
inna
te d
omai
n-sp
ecif
ic k
now
ledg
e of
rel
evan
ce to
suc
h th
ings
as
kins
hip
rela
tions
, I w
ould
not
wan
t to
sugg
est t
hat i
t pro
ves
the
suff
icie
ncy
of a
bla
nket
dom
ain-
gene
ral a
ppro
ach.
Aft
er a
ll, t
here
is c
onsi
dera
ble
pre-
stru
ctur
ing
ofH
into
ns
arch
itect
ure
for
the
disc
over
y of
the
rele
vant
rel
atio
nal i
nfor
mat
ion.
The
ext
ent t
o w
hich
this
pre
-str
uctu
ring
is c
ruci
al is
not
yet
kno
wn.
The
Tim
e-co
urse
of
Dev
elop
men
tal C
hang
eA
noth
er d
omai
n no
w a
vaila
ble
for
expl
orat
ion
is th
e st
udy
of th
e tim
e-co
urse
of
chan
ge. I
n th
is d
omai
n, o
ne q
uest
ion
we
may
con
side
r is
, why
is d
evel
opm
ent
so s
low
? A
s Fl
avel
l (19
63, p
. 49)
put
in h
is b
ook
abou
t Pia
get,
" Wha
t pre
vent
sth
e or
gani
sm f
rom
mas
teri
ng in
one
fel
l sw
oop
all t
hat i
s co
gniz
able
in a
giv
ente
rrai
n?"
The
sam
e qu
estio
n ca
n be
ask
ed o
f co
nnec
tioni
st n
etw
orks
. Her
e, in
case
s lik
e th
e H
into
n ex
ampl
e , w
e ca
n se
e on
e re
ason
why
lear
ning
is g
radu
al.
The
rea
son
is th
at th
e ne
twor
k m
ust i
nteg
rate
the
chan
ges
it m
akes
to it
sco
nnec
tions
ove
r a
suff
icie
nt s
ampl
e of
the
envi
ronm
ent,
so th
at th
e ch
ange
s ca
nbe
gui
ded
by th
e st
ruct
ure
that
is p
rese
nt in
it. I
t is
only
whe
n th
e ch
ange
s oc
cur
slow
ly e
noug
h th
at th
eir
over
all d
irec
tion
is g
over
ned
by th
e st
ruct
ure
of th
een
viro
nmen
t tha
t the
abi
lity
to r
epre
sent
that
str
uctu
re c
an e
mer
ge.
McC
LE
LL
AN
D4. NATURE AND NURTURE
IN D
EV
EL
OPM
EN
T
But
now
a p
uzzl
e se
ems
to a
rise.
If d
evel
opm
ent i
s a
slow
and
gra
dual
pro
cess
,w
hy is
it th
at it
oft
en a
ppea
rs to
be
mar
ked
by lo
ng p
erio
ds o
f st
atis
, pun
ctua
ted
by b
rief
per
iods
of
rela
tivel
y ra
pid
chan
ge?
Wha
t acc
ount
s, in
Fla
vell'
s w
ords
,
for
its "velocity and acceleration" (Flavell, 1
963,
p. 4
9)?
How
is it
, mor
esp
ecif
ical
ly, t
hat i
ncre
men
tal m
echa
nism
s gi
ve r
ise
to a
ppar
ently
qua
litat
ive
chan
ge?
It is
cru
cial
to d
istin
guis
h be
twee
n th
e se
nse
of s
tage
s in
tend
ed in
this
cha
pter
and
the
sens
e of
sta
ges
that
com
es f
rom
the
deve
lopm
enta
l the
ory
of P
iage
t. In
this
cha
pter
, sta
ges
are
only
mea
nt to
ref
er to
per
iods
of
rela
tive
stat
is w
ithin
dom
ains
, and
sta
ge tr
ansi
tions
are
mea
nt a
s re
fere
nces
to th
e tr
ansi
tions
bet
wee
nth
ese
dom
ain-
spec
ific
fea
ture
s of
the
deve
lopm
enta
l pro
file
. Thi
s co
ncep
tion
ofst
ages
con
tras
ts s
harp
ly w
ith th
e Pi
aget
ian
conc
eptio
n of
bro
ad s
tage
s cu
tting
acro
ss a
ll co
gniti
ve d
omai
ns. I
t may
be
that
Pia
get
s in
sist
ence
on
the
cent
ralit
yof
thes
e br
oad
stag
es c
ontr
ibut
ed to
the
diff
icul
ty in
und
erst
andi
ng h
ow h
isvi
ews
of th
e so
urce
s of
cog
nitiv
e ch
ange
-acc
omm
odat
ion
and
assi
mila
tion-
coul
d gi
ve r
ise
to c
ogni
tive
deve
lopm
ent.
In a
ny c
ase.
the
ques
tion
of h
ow a
nd w
hy d
omai
n-sp
ecif
ic s
tage
tran
sitio
nsoc
cur
rem
ains
puz
zlin
g fo
r ex
peri
ence
-bas
ed th
eori
es o
f al
l typ
es. I
f w
e ta
ke a
nin
crem
enta
l vie
w, i
t is
not a
t all
obvi
ous
why
we
shou
ld s
ee a
ppar
ent s
tabi
lity
for
long
per
iods
at a
ll, e
spec
ially
if, a
s of
ten
happ
ens,
thes
e lo
ng p
erio
ds o
fst
abili
ty a
re f
ollo
wed
by
rela
tivel
y ab
rupt
tran
sitio
ns to
a n
ew p
late
au.
One
res
pons
e to
sta
ge tr
ansi
tions
has
bee
n to
arg
ue th
at th
ey d
o no
t rea
llyex
ist-
that
they
rep
rese
nt, p
erha
ps, t
he c
rude
ness
of
our
met
hods
for
ass
essi
ngch
ilden
s ca
paci
ties
at p
artic
ular
poi
nts
in d
evel
opm
ent.
Ano
ther
app
roac
h ha
sbe
en to
thin
k of
them
as
aris
ing
from
som
e m
atur
atio
nal p
roce
ss. O
n th
is v
iew
,th
e ch
ild p
rogr
esse
s fr
om s
tage
to s
tage
bas
ed o
n so
me
exog
enou
s pr
oces
s, m
uch
as a
but
terf
ly p
rogr
esse
s fr
om s
tage
to s
tage
. Bot
h of
thes
e ki
nds
of th
ings
may
be p
art o
f th
e st
ory.
In
addi
tion,
how
ever
, ins
ight
s fr
om th
e st
udy
ofle
arni
ng in
conn
ectio
nist
mod
els
may
als
o sh
ed s
ome
light
on
the
mat
ter.
I ex
amin
ed th
is is
sue
in a
stu
dy o
f de
velo
pmen
tal c
hang
e in
the
bala
nce
scal
etask introduced by Inhelder and Piaget (1958), and subsequently studied
exte
nsiv
ely
by S
iegl
er (
e.g.
197
6, 1
981)
and
man
y ot
hers
. The
task
, qui
te s
impl
y,
is to
look
at b
alan
ce s
cale
pro
blem
s of
the
kind
sho
wn
in F
ig, 4
.7, a
nd to
indi
cate
whi
ch s
ide
will
go
dow
n. T
he s
peci
fic
prob
lem
con
sist
s of
pro
vidi
ng s
ome
num
ber
of u
nit w
eigh
ts o
n ea
ch s
ide,
with
the
wei
ghts
all
on o
ne p
eg, s
ome
num
ber
of s
teps
fro
m th
e fu
lcru
m. S
iegl
er id
entif
ied
seve
ral s
tage
s in
the
deve
lopm
ent
of th
e ab
ility
to s
olve
this
kin
d of
pro
blem
. In
wha
t I w
ill c
all s
tage
0 (
typi
cal o
fch
ildre
n be
low
the
age
of 5
), h
e fo
und
that
chi
ldre
n te
nded
to p
erfo
rm r
ando
mly
in th
e ta
sk. I
n st
age
I, c
hild
ren
resp
onde
d to
the
num
ber
of w
eigh
ts o
n ea
ch s
ide,
but i
gnor
ed d
ista
nce
from
the
fulc
rum
. In
stag
e 2,
chi
ldre
n to
ok d
ista
nce
into
acco
unt o
nly
whe
n th
e w
eigh
ts o
n bo
th s
ides
wer
e th
e sa
me.
In
stag
e 3,
they
took
both
dis
tanc
e an
d w
eigh
t int
o ac
coun
t, bu
t beh
aved
inco
nsis
tent
ly w
hen
thes
etw
o cu
es w
ere
plac
ed in
con
flic
t. St
age
4, w
hich
is n
ot a
lway
s ac
hiev
ed e
ven
by
FIG
. 4.7 A
bala
nce
scal
e of
the
kind
stu
died
by
Sieg
ler
(197
6, 1
981)
. Rep
rodu
ced
by p
enni
ssio
n.A
cade
mic
Pre
ss. (
nc,
adul
ts, r
equi
res
mul
tiply
ing
wei
ght t
imes
dis
tanc
e w
hen
wei
ght i
s gr
eate
r on
one
side
and
the
dist
ance
is g
reat
er o
n th
e ot
her.
The
mai
n in
tere
st f
or n
ow is
in th
etr
ansi
tions
thro
ugh
the
earl
y st
ages
, par
ticul
arly
into
and
out
of
stag
e I,
and
inth
e fa
ct th
at c
hild
ren
typi
cally
sta
y in
sta
ge I
for
sev
eral
yea
rs. T
he q
uest
ion
isho
w is
it th
at th
is s
tage
- lik
e ch
arac
ter
of d
evel
opm
ent c
an a
rise
fro
m a
nin
crem
enta
l lea
rnin
g m
echa
nism
?In
fac
t, th
is k
ind
of s
tage
- lik
e pr
ogre
ssio
n is
exa
ctly
wha
t we
typi
cally
see
inco
nnec
tioni
st le
arni
ng m
odel
s, T
he p
heno
men
on r
equi
res
a m
ulti-
laye
rne
twor
k--o
ne c
onsi
stin
g of
at l
east
one
laye
r of
hid
den
units
bet
wee
n in
put a
ndou
tput
. In
the
sim
ples
t pro
blem
s th
at r
equi
re a
two-
laye
r ar
chite
ctur
e-lik
e th
eex
clus
ive-
or p
robl
em, s
how
n in
Fig
. 4.
ther
e ar
e tw
o st
ages
, In
this
pro
blem
,it
is s
tand
ard
to u
se a
net
wor
k co
nsis
ting
of tw
o in
put u
nits
, tw
o hi
dden
uni
tsan
d on
e ou
tput
, and
the
task
the
netw
ork
face
s is
to le
arn
that
the
outp
ut u
nit
shou
ld b
e on
if e
ither
inpu
t uni
t is
on, b
ut s
houl
d be
off
if n
eith
er o
r bo
th a
re o
n.In
trai
ning
suc
h ne
twor
ks w
ith m
ultip
le s
wee
ps th
roug
h th
e se
t of
trai
ning
exam
ples
, we
see
an e
arly
sta
ge in
whi
ch le
arni
ng p
rogr
esse
s ve
ry s
low
ly, a
ndth
e ne
twor
k is
per
fonn
ing
very
poo
rly,
pro
duci
ng th
e sa
me
resp
onse
in e
very
case
-an
activ
atio
n of
0. 5
. The
re th
en fo
llow
s a
rapi
d tr
ansi
tion
, in
whi
chpe
rfon
nanc
e ra
pidl
y im
prov
es, u
ntil
it le
vels
off
at a
hig
h le
vel o
f ac
cura
cy, i
nw
hich
the
outp
ut o
f th
e ne
twor
k ap
proa
ches
the
righ
t ans
wer
for
all
four
trai
ning
case
s. I
n m
ore
com
plex
cas
es, w
here
som
e of
the
trai
ning
exa
mpl
es a
re e
asie
rto master than others, there can be multiple plateaus
, aga
in p
unct
uate
d by
rela
tivel
y ra
pid
tran
sitio
ns.
The
beh
avio
ur in
the
sim
ples
t cas
es c
an b
e un
ders
tood
in th
e fo
llow
ing
way
.E
arly
on,
bot
h in
put a
nd o
utpu
t con
nect
ions
in th
e ne
twor
k ar
e ra
ndom
. A c
hang
eto
a c
onne
ctio
n w
eigh
t on
the
inpu
t sid
e of
the
netw
ork
has
no u
sefu
l eff
ect,
sinc
eth
e ou
tput
con
nect
ions
are
ran
dom
; and
a c
hang
e to
a c
onne
ctio
n w
eigh
t on
the
outp
ut s
ide
of th
e ne
twor
k ha
s no
use
ful e
ffec
t, si
nce
the
inpu
t con
nect
ions
are
rand
om. G
radu
ally
, tho
ugh,
thro
ugh
the
cour
se o
f ex
peri
ence
, the
con
nect
ion
wei
ghts
beg
in to
bec
ome
coor
dina
ted.
The
inpu
t wei
ghts
beg
in to
pro
duce
use
ful
repr
esen
tatio
ns, a
nd th
e ou
tput
wei
ghts
beg
in to
pro
duce
use
ful p
redi
ctio
nsba
sed
on th
ese
repr
esen
tatio
ns, A
s th
is h
appe
ns, i
t tur
ns o
ut th
at s
mal
l cha
nges
to th
e w
eigh
ts b
egin
to p
rodu
ce b
igge
r an
d bi
gger
cha
nges
in p
erfo
nnan
ce.
McC
LE
LL
AN
D
XOR Network
Inpu
tO
utpu
t
4. NATURE AND NURTURE
IN D
EV
EL
OPM
EN
T
used
to a
sses
s ch
ildre
ns
perf
onna
nce
at e
ach
poin
t alo
ng th
e w
ay. I
ran
the
netw
ork
seve
ral t
imes
, usi
ng d
iffe
rent
sta
rtin
g w
eigh
ts a
nd d
iffe
rent
ran
dom
sequ
ence
s of
trai
ning
tria
ls, a
nd f
ound
that
it c
aptu
red
seve
ral a
spec
ts o
fch
ildre
ns
perf
onna
nce
very
nic
ely.
In g
ener
al, I
foun
d th
at th
e si
mul
atio
nco
nfon
ned
to o
ne o
f Sie
gler
s st
ages
abo
ut 8
6% o
f th
e tim
e-in
chi
ldre
n, th
efi
gure
is a
roun
d 93
%. M
ore
grad
ual l
earn
ing
prod
uces
a h
ighe
r le
vel o
fco
nfon
nity
(Sc
hmid
t & S
chul
tz, 1
992)
. The
net
wor
k al
way
s pr
ogre
ssed
fro
mst
age
0 to
sta
ge I
, and
then
aft
er a
per
iod
of s
tabi
lity
it ex
hibi
ted
a no
isy
tran
sitio
nth
roug
h st
age
2 to
a s
tage
rep
rese
ntin
g so
met
hing
inte
nned
iate
bet
wee
n Si
egle
rst
ages
3 a
nd 4
. In
so d
oing
, it c
aptu
red
a nu
mbe
r of
asp
ects
of
the
data
, inc
ludi
ngso
me
of th
e fe
atur
es th
at in
dica
te th
at c
hild
ren
may
use
a c
ontin
uous
fun
ctio
n,ra
ther
than
dis
cret
e ru
les,
in m
akin
g th
eir
judg
emen
ts in
the
bala
nce
scal
e ta
sk(W
ilken
ing
& A
nder
son,
199
1; s
ee S
chm
idt &
Sch
ultz
, 199
2, a
nd M
cCle
lland
& Jenkins, 1991
, for
fur
ther
dis
cuss
ion)
.I
did
find
that
in o
rder
to s
imul
ate
the
resu
lts, i
t was
nec
essa
ry to
mak
e tw
oas
sum
ptio
ns. F
irst,
I ha
d to
ass
ume
that
wei
ght a
nd d
ista
nce
wer
e en
code
dse
para
tely
, as
show
n in
the
sim
ple
netw
ork
, and
com
bine
d on
ly a
fter
sep
arat
een
codi
ng. S
econ
d, I
had
to p
rovi
de-
som
e ba
sis
for
the
use
of th
e di
stan
ce c
ue to
deve
lop
mor
e sl
owly
than
the
use
of th
e w
eigh
t cue
. I g
ot th
e re
sults
just
sho
wn
usin
g th
e as
sum
ptio
n th
at w
eigh
t var
ies
mor
e of
ten
in th
e re
leva
nt e
xper
ienc
e
-""'
"
FIG
. 4.8 XOR:
The
net
wor
k. th
e in
put-
()ut
put p
atte
rns
and
the
time-
cour
se o
f ac
quis
ition
.
Dis
tonc
e
Whi
le it
see
ms
like
no p
rogr
ess
is b
eing
mad
e at
all
at f
irst
, in
fact
ther
e is
som
epr
ogre
ss a
ll al
ong.
The
ear
ly p
hase
s pr
oduc
e on
ly v
ery
smal
l cha
nges
in o
vert
perf
onna
nce,
but
they
are
nec
essa
ry to
bri
ng th
e ne
twor
k to
the
poin
t whe
re it
is c
apab
le o
f m
ore
rapi
d an
d no
ticea
ble
prog
ress
. Lat
er r
apid
cha
nge
depe
nds
upon
the
earl
ier,
som
etim
es a
lmos
t inf
inite
sim
ally
sm
all a
dapt
atio
ns.
In a
pply
ing
thes
e id
eas
in a
n ef
fort
to u
nder
stan
d de
velo
pmen
t in
the
bala
nce
scal
e pr
oble
m, w
e ca
n en
visi
on a
pro
gres
sion
in w
hich
the
kind
of
tran
sitio
n w
ese
e in
the
XO
R n
etw
ork
happ
ens,
firs
t for
one
cue
-the
wei
ght c
ue-a
nd th
enfo
r th
e di
stan
ce c
ue. I
ndee
d, i
t is
poss
ible
to s
imul
ate
the
prog
ress
ion
of s
tage
sin
just
this
way
(M
cCle
lland
, 198
9; M
cCle
lland
& J
enki
ns, 1
991;
Sch
mid
t &Sc
hultz
, 199
2). I
n th
e si
mul
atio
ns r
epor
ted
in M
cCle
lland
(19
89),
I s
et u
p a
netw
ork
in w
hich
the
inpu
ts w
ere
a re
pres
enta
tion
of a
bal
ance
sca
le p
robl
em,
indi
catin
g so
me
num
ber
of w
eigh
ts s
ome
num
ber
of s
teps
fro
m th
e fu
lcru
m o
nea
ch s
ide
(Fig
. 4.9
). T
he ta
sk w
as s
impl
y to
turn
on
one
of tw
o ou
tput
s, in
dica
ting
whi
ch s
ide
shou
ld g
o do
wn.
The
net
wor
k w
as tr
aine
d on
a r
ando
m s
eque
nce
ofba
lanc
e sc
ale
prob
lem
s, a
nd w
as te
sted
with
the
sam
e pr
oble
ms
that
Sie
gler
(19
81)
Wei
ght
0008
008
000
FIG
. 4.
The
con
nect
ioni
st n
etw
ork
used
to s
tudy
sta
ge tr
ansi
tions
by
McC
lella
nd (
1989
).R
epro
duce
d by
per
mis
sion
, Oxf
ord
Uni
vers
ity P
ress
, New
Yor
k.
NA
TU
RE
AN
D N
UR
TU
RE
IN D
EV
ELO
PM
EN
T
Hid
den
to O
utpu
t
1\1
C)I
100
Epo
ch
Inpu
t to
Hid
den
~ N
(.)
C)I
100
Epo
ch
McC
LE
LL
AN
D
of th
e ch
ild th
an d
ista
nce
does
-in
the
sim
ulat
ions
, thi
s am
ount
s to
usi
ng m
ore
freq
uent
pre
sent
atio
ns o
f ca
ses
in w
hich
wei
ght d
iffe
rs o
n th
e tw
o si
des
of th
esc
ale
but d
ista
nce
is th
e sa
me,
by
anal
ogy
to c
hild
ren
s ex
peri
ence
with
see
-saw
s,w
here
dis
tanc
e fr
om th
e fu
lcru
m is
rel
ativ
ely
fixe
d by
the
situ
atio
n. M
ore
rece
ntly
, I h
ave
exam
ined
the
idea
that
dis
tanc
e is
a m
ore
com
plex
rel
atio
n th
anw
eigh
t, W
eigh
t is
(at l
east
in a
fix
ed g
ravi
tatio
nal f
ield
) a
one-
plac
e pr
edic
ate-
a pr
oper
ty o
f an
indi
vidu
al o
bjec
t. In
con
tras
t, di
stan
ce b
etw
een
two
obje
cts
isa
two-
plac
e pr
edic
ate,
a r
elat
ion
betw
een
an o
bjec
t and
ano
ther
obj
ect-in this
case
, the
wei
ght a
nd th
e fu
lcru
m. T
o ca
ptur
e th
is id
ea, I
use
d a
mor
e co
mpl
exin
put,
in w
hich
the
posi
tion
of th
e weights and of the fulcrum could vary
(McC
lella
nd, i
n pr
ess)
. Thi
s m
ade
it ne
cess
ary
for
the
netw
ork
to le
arn
to c
ompu
teth
e m
ore
com
plex
dis
tanc
e cu
e fr
om th
e si
mpl
er p
ositi
on c
ues.
In
that
cas
e, e
ven
if w
eigh
t and
dis
tanc
e va
ry e
qual
ly o
ften
in th
e tr
aini
ng e
xam
ples
, the
net
wor
kle
arns
the
wei
ght c
ue m
uch
mor
e qu
ickl
y, a
nd th
ere
is a
long
pha
se th
atco
rres
pond
s to
Sie
gler
s ru
le I
, fol
low
ed e
vent
ually
by
a tr
ansi
tion
to a
sta
gelik
e Si
egle
rs
rule
3, i
n w
hich
wei
ght a
nd d
ista
nce
are
both
con
side
red.
In th
e w
ork
with
the
sim
pler
rep
rese
ntat
ion
(McC
lella
nd, 1
989)
, it i
s ea
sy to
exam
ine
the
time-
cour
se o
f le
arni
ng a
bout
the
wei
ght a
nd d
ista
nce
cues
, in
term
s
of th
e st
reng
ths
of th
e co
nnec
tion
wei
ghts
into
and
out
of
the
hidd
en u
nits
(Fi
g.10
). F
or b
oth
cues
, we
see
roug
hly
the
sam
e pa
ttern
. Ini
tially
, the
net
wor
k is
inse
nsiti
ve to
the
cue
at b
oth
leve
ls. T
hen
ther
e is
a r
elat
ivel
y st
eep
tran
sitio
n,fo
llow
ed b
y a
leve
lling
off
, The
tran
sitio
n is
mor
e ra
pid
for
the
wei
ght c
ue th
anth
e di
stan
ce c
ue, b
ecau
se o
f di
ffer
entia
l fre
quen
cy o
f ex
posu
re to
var
iatio
ns in
the
two
cues
. The
re a
re a
ctua
lly m
any
empi
rica
l res
ults
sup
port
ing
the
idea
that
the
acqu
isiti
on o
f th
e di
stan
ce c
ue is
rel
ativ
ely
grad
ual i
n ch
ildre
n, a
s it
is in
the
mod
el (
e,g.
Wilk
enin
g &
And
erso
n, 1
991)
. The
key
poi
nt th
ough
is th
e no
n-ho
mog
enei
ty o
f th
e de
velo
pmen
tal p
roce
ss, b
oth
for
the
wei
ght c
ue a
nd th
edi
stan
ce c
ue. I
n bo
th c
ases
, the
re is
an
earl
y ph
ase
of n
o ov
ert c
hang
e, f
ollo
wed
by a
mor
e ra
pid
tran
sitio
n to
a n
ew le
vel.
Of
cour
se, t
his
sim
ulat
ion
vast
ly o
vers
impl
ifie
s th
e ch
alle
nges
a le
arne
r fa
ces
duri
ng d
evel
opm
ent.
Chi
ldre
n do
not
lear
n ab
out b
alan
ce s
cale
s in
isol
atio
nfr
om o
ther
kin
ds o
f ex
peri
ence
with
dis
tanc
e an
d w
eigh
t inf
orm
atio
n. D
ista
nces
and
wei
ghts
do
not c
ome
nice
ly p
repa
ckag
ed in
uni
t qua
ntiti
es, a
s th
ey d
o in
the
inpu
t to
the
netw
ork.
Nev
erth
eles
s, I
thin
k th
e m
odel
doe
s ca
ptur
e on
e im
port
ant
aspe
ct o
f de
velo
pmen
t, na
mel
y its
sta
ge-l
ike
char
acte
r in
man
y di
ffer
ent d
omai
ns.
In s
umm
ary,
then
, we
see
that
con
nect
ioni
st m
odel
s ca
n sh
ed s
ome
light
on
the
time-
cour
se o
f de
velo
pmen
t. T
he w
ork
does
not
trea
t the
pro
cess
as
one
that
ari
ses
stri
ctly
fro
m e
nvir
onm
enta
l inf
luen
ces.
Ind
eed,
the
mod
el il
lust
rate
s th
e ge
nera
lim
port
ance
' of ar
chite
ctur
al c
onst
rain
ts, s
ince
it is
cle
ar th
at th
e su
cces
s of
the
mod
elde
pend
s on
the
sepa
rate
enc
odin
g of
wei
ght a
nd d
ista
nce
info
rmat
ion.
Exp
erie
nce
is n
ot th
e on
ly f
acto
r th
at p
lays
a r
ole
in s
hapi
ng d
evel
opm
ent.
But
exp
erie
nce
isth
e en
gine
that
dri
ves
deve
lopm
ent f
orw
ard,
and
the
wor
k m
akes
it c
lear
how
sta
ge-
like
beha
viou
r ca
n em
erge
fro
m in
crem
enta
l lea
rnin
g m
echa
nism
s.
F~
G. 1
4.10
Tim
e-co
urse
of
acqu
isiti
on o
f co
nnec
tion
stre
ngth
s re
leva
nt to
the
role
of
wei
ght a
nddi
stan
ce in
the
bala
nce
scal
e si
mul
atio
n of
McC
lella
nd (
1989
), R
epro
duce
d by
pen
niss
ion.
Oxf
ord
Uni
vers
ity P
ress
, New
Yor
k.
It is
wor
th s
topp
ing
for
a m
omen
t to
note
how
muc
h th
e co
nnec
tioni
st a
ppro
ach
adva
nces
our
und
erst
andi
ng o
f th
e m
echa
nism
s of
dev
elop
men
tal c
hang
e, r
elat
ive
to p
ropo
sals
adv
ance
d, f
or e
xam
ple,
by
Piag
et. P
iage
t pre
sent
ed h
is th
inki
ng in
4, NATURE AND NURTURE
IN D
EV
EL
OPM
EN
TM
cCL
EL
LA
ND
tenn
s of
the
idea
s of
equ
ilibr
atio
n, a
ccom
mod
atio
n an
d as
sim
ilatio
n (s
ee F
lave
ll,19
63, f
or a
con
cise
pre
sent
atio
n). T
hese
idea
s su
gges
t pro
cess
es o
f co
ntin
ual,
grad
ual a
dapt
atio
n, a
nd a
s su
ch c
aptu
re th
e ge
nera
l fac
t tha
t cog
nitiv
ede
velo
pmen
t is
a ve
ry s
low
pro
cess
, spa
nnin
g ve
ry m
any
year
s. B
ut th
ey d
o no
tre
ally
pro
vide
any
cle
ar o
r ex
plic
it ba
sis
for
unde
rsta
ndin
g w
hy th
ere
are
plat
eaus
in d
evel
opm
ent i
nter
sper
sed
with
per
iods
of
rapi
d ch
ange
. Per
haps
in p
art f
orth
is r
easo
n, e
xper
ienc
e-ba
sed
acco
unts
of
deve
lopm
enta
l cha
nge
have
tend
ed to
fall
from
fav
our,
with
man
y in
vest
igat
ors
pref
erri
ng to
pro
pose
inst
ead
dist
inct
lym
atur
atio
nal a
ccou
nts
(e.g. Case, 1978; Pascual-L
eone
, 198
7). M
y po
int i
sno
t tha
t the
se m
atur
atio
nal a
ccou
nts
are
wro
ng, b
ut th
at w
e ar
e no
w in
a p
ositi
onth
at a
llow
s ex
perie
nce-
base
d al
tern
ativ
es to
be
give
n an
exp
licit
mec
hani
stic
bas
isth
at a
llow
s fo
r fu
ller
and
mor
e de
taile
d ex
plor
atio
n.
capa
bilit
ies,
over and above object pennanence
per se.
It h
as b
een
prop
osed
(Bai
llarg
eon
, 199
3; B
ailla
rgeo
n, G
rabe
r, D
eVos
, & B
lack
, 199
0; D
iam
ond,
1991
; Spe
lke
et a
I., 1
992)
that
you
ng c
hild
ren
know
that
obj
ects
that
they
can
no lo
nger
see
are
stil
l pre
sent
, but
lack
the
abili
ty to
per
form
mea
ns-e
nds
anal
ysis
-to
real
ise
that
they
mus
t per
fonn
an
indi
rect
ly r
elev
ant a
ctio
n, s
uch
as r
emov
ing
the
cove
ring
, fir
st. T
hink
ing
ofth
is k
ind
is o
f co
urse
con
sist
ent w
ithna
tivis
t app
roac
hes,
like
thos
e pr
opos
ed b
y Sp
elke
et a
I., i
n w
hich
it is
sup
pose
dth
at th
e ch
ild h
as a
n in
nate
cap
acity
to r
epre
sent
and
rea
son
abou
t the
con
tinue
dex
iste
nce
of in
visi
ble
obje
cts,
but
has
faile
d to
acq
uire
som
e an
cilla
ry s
kill
need
ed f
or th
e ex
pres
sion
of
this
kno
wle
dge
in c
erta
in ta
sks.
The
fra
mew
ork
for
thin
king
abo
ut d
evel
opm
ent i
n co
nnec
tioni
st te
rms,
how
ever
, lea
ds to
a v
ery
diff
eren
t way
of
thin
king
abo
ut w
hat m
ay b
e go
ing
onin
this
cas
e. F
irst
, it s
eem
s en
tirel
y na
tura
l to
supp
ose
that
the
abili
ty to
per
fonn
in ta
sks
like
Bai
llarg
eon
s ar
ises
fro
m th
e im
plic
it pr
edic
tive
kind
of
lear
ning
that
we
have
bee
n co
nsid
erin
g th
roug
hout
this
cha
pter
. In
the
cour
se o
f ob
serv
ing
the
wor
ld a
roun
d th
em, y
oung
chi
ldre
n co
uld
deve
lop
the
abili
ty to
pre
dict
fut
ure
even
ts b
ased
on
the
curr
ent i
nput
and
on
prec
edin
g co
ntex
t. Su
ch p
redi
ctio
nsca
n co
me
to r
efle
ct a
sen
sitiv
ity to
obj
ects
that
are
not
in f
act v
isib
le f
or a
t lea
sta
shor
t per
iod
of ti
me
befo
re th
e pr
edic
ted
even
t, as
in B
ailla
rgeo
ns
task
. Ind
eed,
Mun
akat
a (p
ers.
com
m.)
has
trai
ned
a re
curr
ent n
etw
ork
(sho
wn
in F
ig. 4
.11) to
antic
ipat
e th
e fu
ture
pos
ition
s of
obj
ects
mov
ing
acro
ss a
sim
ulat
ed d
ispl
ay, a
ndto
pre
dict
the
reap
pear
ance
of
thes
e ob
ject
s w
hen
they
dis
appe
ar b
ehin
d ba
rrie
rs,
base
d on
thei
r po
sitio
n an
d di
rect
ion
of m
otio
n at
the
poin
t whe
n th
eydi
sapp
eare
d. T
he id
ea is
that
low
er le
vels
of
visu
al p
roce
ssin
g pr
ojec
t the
dis
play
,
The
Sou
rce
and
Mea
ning
of E
arly
Com
pete
nce
Let
us
now
con
side
r th
e ph
enom
enon
of
earl
y co
mpe
tenc
e-fo
r ex
ampl
e, th
e
fact
that
a y
oung
chi
ld c
an o
ften
exh
ibit
surp
rise
whe
n sh
own
an e
vent
that
vio
late
sba
sic
phys
ical
reg
ular
ities
suc
h as
obj
ect p
erm
anen
ce. W
hat i
s th
e m
eani
ng o
fth
is k
ind
of b
ehav
iour
? Sp
elke
(19
91; S
pelk
e et
aI.
, 199
2) a
nd o
ther
s (e
.g. K
eil,
1991
a, 1
991b
) ha
ve u
sed
it to
sug
gest
that
the
child
pos
sess
es c
erta
in in
nate
prin
cipl
es c
hara
cter
isin
g th
e ph
ysic
al w
orld
. But
is th
is a
nec
essa
ry in
terp
reta
tion?
Let
us
cons
ider
the
obje
ct p
enna
nenc
e ca
se a
s an
exa
mpl
e. W
e w
ill s
ee th
at th
ena
tivis
t app
roac
h an
d th
e PD
P ap
proa
ch p
rovi
de v
ery
diff
eren
t way
s to
ana
lyse
the
beha
viou
ral e
vide
nce.
Piag
et s
how
ed, i
n so
me
of h
is m
ost f
amou
s w
ork,
six
sta
ges
of d
evel
opm
ent
ofth
e ob
ject
con
cept
. His
met
hod
invo
lved
sho
win
g th
e ch
ild a
n ob
ject
, and
then
hidi
ng it
, by
putti
ng it
und
er s
omet
hing
like
a b
lank
et. Y
oung
chi
ldre
n, b
elow
the
age
of 9
mon
ths
or s
o, w
ill n
ot r
etri
eve
such
a h
idde
n ob
ject
, and
the
clas
sica
lin
terp
reta
tion
was
that
they
no
long
er r
epre
sent
its
exis
tenc
e w
hen
it is
out
of
sigh
t. A
fter
9 m
onth
s, th
e ch
ild is
cap
able
of
succ
essf
ul r
etri
eval
und
er th
ese
cond
ition
s, d
emon
stra
ting,
acc
ordi
ng to
the
Piag
etia
n vi
ew, s
ucce
ssfu
l mas
tery
of th
e fo
urth
sta
ge in
the
deve
lopm
ent o
f the
obj
ect c
once
pt. S
ince
Pia
get'
s w
ork,
how
ever
, man
y re
sear
cher
s ha
ve c
halle
nged
his
vie
w th
at c
hild
ren
lack
a c
once
ptof
obj
ect p
enna
nenc
e be
fore
9 m
onth
s. I
t has
bee
n sh
own
in v
ario
us w
ays
that
child
ren
are
sens
itive
to o
bjec
ts th
ey c
an n
o lo
nger
see
. For
exa
mpl
e, B
ailla
rgeo
n(1
987;
Bai
llarg
eon,
Spe
lke,
& W
asse
nnan
, 198
5) h
abitu
ated
chi
ldre
n to
the
site
of a
dra
wbr
idge
ope
ning
and
clo
sing
. The
chi
ldre
n th
en s
aw a
blo
ck p
lace
d in
the
path
of
the
draw
brid
ge, p
ositi
oned
in s
uch
a w
ay th
at a
s th
e dr
awbr
idge
sw
ung
the
bloc
k di
sapp
eare
d fr
om th
e in
fant
s' lo
ok lo
nger
if th
e dr
awbr
idge
sw
ung
thro
ugh
the
loca
tion
occu
pied
by
the
bloc
k, a
s th
ough
the
bloc
k ha
d ce
ased
toex
ist,
sugg
estin
g th
ey a
re s
ensi
tive
to th
e co
ntin
ued
exis
tenc
e of
the
bloc
k.O
ne p
ossi
ble
conc
lusi
on f
rom
this
res
earc
h is
that
the
obje
ct c
once
pt is
act
ually
pres
ent i
n ve
ry y
oung
chi
ldre
n, a
nd th
at P
iage
ts
task
s si
mpl
y re
quir
ed a
dditi
onal
Dis
play
FIG
. 4.11 Munakata
s re
curr
ent n
etw
ork
for
lear
ning
to a
ntic
ipat
e th
e fu
ture
pos
ition
s of
obj
ects
.
McC
LE
LL
AN
D4. NATURE AND NURTURE
IN D
EV
EL
OPM
EN
T
in w
hich
the
obje
ct m
oves
, int
o a
perc
ept,
whi
ch is
like
ly to
be
rich
ly s
truc
ture
dve
ry e
arly
to p
rovi
de u
sefu
l rep
rese
ntat
ions
of
obje
cts
and
thei
r re
lativ
e lo
catio
nin
thre
e-di
men
sion
al s
pace
. The
net
wor
k is
trai
ned
by s
how
ing
it si
mpl
e ob
ject
sm
ovin
g ac
ross
a f
ield
of
view
, som
etim
es c
ol1i
ding
with
oth
er o
bjec
ts a
ndst
oppi
ng, a
nd s
omet
imes
mov
ing
eith
er in
fro
nt o
f or
beh
ind
thes
e ob
ject
s. I
nth
e la
tter
case
, the
mov
ing
obje
ct b
ecom
es in
visi
ble,
but
the
netw
ork
can
lear
nto
trac
k it,
usi
ng it
s pr
evio
us in
tern
al r
epre
sent
atio
n as
inpu
t to
the
form
atio
n of
subs
eque
nt in
tern
al r
epre
sent
atio
ns. T
he n
etw
ork
can
also
use
thes
e in
tern
alre
pres
enta
tions
to p
redi
ct th
e m
omen
t of
the
obje
cts
reap
pear
ance
fro
m b
ehin
dth
e ba
rrie
r. I
f th
e ob
ject
doe
s no
t rea
ppea
r, th
ere
is a
dis
crep
ancy
bet
wee
n th
epr
edic
tion
and
the
obse
rved
eve
nt. S
uch
a di
scre
panc
y m
ay b
e th
e si
gnal
that
caus
es c
hild
ren
to in
crea
se lo
okin
g w
hen
surp
risi
ng e
vent
s oc
cur,
eith
er in
rea
llif
e or
in d
evel
opm
enta
l exp
erim
ents
. In
any
case
, the
key
poi
nt is
that
the
netw
ork
com
es to
acq
uire
inte
rnal
rep
rese
ntat
ions
, not
par
t of
the
perc
ept i
tsel
f,th
at tr
ack
the
mov
emen
t of t
he o
bjec
t beh
ind
the
barr
ier,
and
to p
redi
ct it
sre
appe
aran
ce o
n th
e ot
her
side
.In
the
cont
ext o
f su
ch n
etw
orks
, the
re is
no
reas
on w
hy th
e ab
ility
to m
ake
perc
eptu
al p
redi
ctio
ns w
ould
nec
essa
rily
impl
y an
abi
lity
to r
each
for
an
obje
ctth
e ch
ild c
an n
o lo
nger
see
, Tw
o po
ssib
ilitie
s ar
e sh
own
in F
ig. 4
.12.
Acc
ordi
ng
to th
e fir
st, r
elev
ant p
arts
of t
he m
otor
sys
tem
may
rec
eive
inpu
t ini
tial1
y fr
omth
e pe
rcep
tual
rep
rese
ntat
ion
itsel
f, a
nd n
ot f
rom
the
inte
rnal
rep
rese
ntat
ion
need
ed f
or m
akin
g pe
rcep
tual
pre
dict
ions
. Whe
n th
e ob
ject
is h
idde
n, th
e in
tern
alre
pres
enta
tion
may
ref
lect
its continued existence, but the object is not
repr
esen
ted
in th
e pe
rcep
t its
elf
at th
is ti
me,
and
so
wou
ld n
ot b
e in
a p
ositi
onto
gov
ern
reac
hing
, On
this
acc
ount
, lat
er d
evel
opm
ent o
f co
nnec
tions
bet
wee
nth
e in
tern
al r
epre
sent
atio
ns a
nd th
e m
otor
sys
tem
wou
ld b
e ne
cess
ary
befo
re th
ech
ild c
ould
rea
ch f
or u
nsee
n ob
ject
s. T
he s
econ
d po
ssib
ility
is th
at r
each
ing
isba
sed
only
on
the
inte
rnal
rep
rese
ntat
ions
, but
the
inte
rnal
rep
rese
ntat
ions
for
visi
ble
obje
cts
are
sim
ply
stro
nger
than
the
repr
esen
tatio
ns o
f ob
ject
s th
at a
reno
t dir
ectly
vis
ible
. Aft
er a
l1, w
hen
the
obje
ct is
vis
ible
ther
e ar
e tw
o so
urce
s of
inpu
t, th
e pe
rcep
t and
the
prio
r in
tern
al s
tate
, whe
reas
whe
n th
e ob
ject
is in
visi
ble
there is only the prior internal state to sustain the representation. Su
ch a
repr
esen
tatio
n m
ight
eas
ily. b
e st
rong
eno
ugh
to s
usta
in p
erce
ptua
l pre
dict
ions
stro
ngly
eno
ugh
to e
licit
a m
ild s
urpr
ise
reac
tion
in ta
sks
like
Bai
llarg
eon
with
out b
eing
str
ong
enou
gh to
sup
port
str
uctu
red
reac
hing
beh
avio
ur.
Mun
akat
a (1
992)
car
ried
out
an
expe
rim
ent t
o tr
y to
dis
tingu
ish
poss
ibili
ties
such
as
thes
e fr
om th
e m
eans
~nd
s ty
pe o
f int
erpr
etat
ion,
She
firs
t atte
mpt
ed to
trai
n 7-
mon
th-o
ld c
hild
ren
to r
etrie
ve o
bjec
ts p
lace
d on
top
of a
tow
el, a
t adi
stan
ce o
f a
coup
le o
f fe
et f
rom
them
. Man
y ch
ildre
n le
arne
d to
per
form
the
task
suc
cess
ful1
y. S
he th
en g
ave
the
succ
essf
ul c
hild
ren
test
tria
ls, i
n w
hich
the
obje
ct w
as f
irst
pla
ced
on th
e to
wel
, and
then
a s
cree
n w
as p
ul1e
d in
fro
nt o
f it.
In o
ne c
ase,
the
scre
en w
as tr
ansp
aren
t. In
the
othe
r ca
se, t
he s
cree
n w
as o
paqu
e,an
d pr
even
ted
the
child
fro
m s
eein
g th
e ob
ject
. Acc
ordi
ng to
the
clai
m th
at
Inac
cess
ible
rep
rese
ntat
ions
:
Inte
rnal
Rep
rese
ntat
ion
crl
Perc
ept
Res
pons
eSy
stem
s
Dis
play
Wea
ker
repr
esen
tatio
n of
invi
sibl
e ob
ject
s:
Inte
rnal
Rep
rese
ntat
ion
Res
pons
eSy
stem
s
Perc
ept
Dis
play
FIG
.12 Two
poss
ible
net
wor
k ac
coun
ts o
f fa
ilure
to r
each
for
obj
ects
who
se r
eapp
eara
nce
from
behi
nd a
bar
rier
can
be
antic
ipat
ed.
child
ren
s fa
ilure
to r
etrie
ve h
idde
n ob
ject
s is
due
to a
failu
re o
f mea
ns~
nds
anal
ysis
, the
se c
hild
ren
, who
hav
e no
w b
een
give
n th
e re
leva
nt m
eans
, sho
uld
have
bee
n ab
le to
ret
riev
e th
e ob
ject
s ju
st a
s w
el1
whe
ther
it w
as v
isib
le o
r no
t.In
fact
, tho
ugh,
Mun
akat
a fo
und
that
chi
ldre
n of
7 m
onth
s w
ere
muc
h m
ore
likel
yto
ret
riev
e th
e ob
ject
whe
n th
e sc
reen
was
tran
spar
ent t
han
whe
n it
was
opa
que.
Whe
n th
e sc
reen
was
opa
que,
they
wer
e no
mor
e lik
ely
to p
ul1
the
tow
el w
hen
a to
y w
as p
rese
nt th
an w
hen
it w
as a
bsen
t.T
he r
esul
ts p
rese
nt a
puz
zle
from
a p
oint
of
view
in w
hich
we
trea
t the
abi
lity
to r
epre
sent
obj
ects
that
are
no
long
er v
isib
le a
s a
disc
rete
abi
lity
that
the
child
4. NATURE AND NURTURE
IN D
EV
EL
OPM
EN
TM
cCL
EL
LA
ND
eith
er h
as o
r do
es n
ot h
ave
(Spe
lke
et a
I., 1
992)
, Chi
ldre
n de
mon
stra
te s
ensi
tivity
to o
bjec
ts th
ey c
ant s
ee in
set
tings
like
Bai
llarg
eon
s, b
ut y
et d
o no
t exh
ibit
this
sens
itivi
ty in
a ta
sk li
ke M
unak
ata
s, w
here
the
mea
ns-e
nds
inte
rpre
tatio
n ha
s be
enru
led
out.
Thu
s th
e re
sults
see
m o
n th
e on
e ha
nd to
sup
port
, and
on
the
othe
r to
cont
radi
ct, t
he c
laim
of
Spel
ke e
t aI.
(19
92, p
. 606
) th
at y
oung
chi
ldre
n "c
an
repr
esen
t sta
tes
of th
e w
orld
that
they
can
no
long
er p
erce
ive
. But
the
resu
lts c
an
be a
ccou
nted
for
in te
nns
of id
eas
that
see
m p
erfe
ctly
str
aigh
tfor
war
d w
hen
we
thin
k ab
out t
he p
robl
em f
rom
a P
DP
pers
pect
ive.
The
kno
wle
dge
that
sub
serv
es
perc
eptu
al a
ntic
ipat
ions
is s
tore
d in
the
fonn
of
conn
ectio
n w
eigh
ts, a
nd a
s su
ch
may
be
imbe
dded
in p
arts
of
the
syst
em th
at p
rodu
ce r
epre
sent
atio
ns th
at a
re n
otin
itial
ly u
sed
to g
over
n re
achi
ng. E
ven
if th
ey a
re u
sed
to g
over
n re
achi
ng, t
hest
reng
th o
f th
ese
conn
ectio
ns m
ight
not
be
stro
ng e
noug
h to
sup
port
a c
ompl
exbe
havi
our
such
as
read
ing,
eve
n if
they
can
sup
port
a m
ild s
urpr
ise
reac
tion
whe
nat
ypic
al p
erce
ptua
l seq
uela
e oc
cur.
Mun
akat
as
expe
rim
ent d
oes
not,
of c
ours
e,de
mon
stra
te d
irec
tly th
at th
e ab
ility
to p
erfo
nn p
erce
ptua
l ant
icip
atio
ns is
acq
uire
d.B
ut it
is c
onsi
sten
t with
the
idea
that
see
ms
quite
nat
ural
fro
m a
PD
P pe
rspe
ctiv
eth
at c
apab
ilitie
s ex
hibi
ted
in p
erce
ptua
l exp
erim
ents
do
not n
eces
sari
ly r
efle
ct th
efu
ll-bl
own
inna
te p
rese
nce
of c
once
pts
such
as
obje
ct p
enna
nenc
e.T
o su
mm
aris
e th
is s
ectio
n, I
hav
e tr
ied
to s
how
how
it m
ight
be
frui
tful
toth
ink
of e
arly
com
pete
nce
as r
efle
ctin
g th
e ea
rlie
st d
evel
opin
g as
pect
s of
aca
paci
ty to
pre
dict
the
futu
re b
ased
on
the
pres
ent a
nd th
e pa
st, a
nd I
hav
e tr
ied
to in
dica
te h
ow s
uch
an id
ea m
ay b
e at
leas
t as
plau
sibl
e as
an
appr
oach
bas
edon
inna
te k
now
ledg
e of
gen
eral
pri
ncip
les.
Aga
in, t
houg
h, I
wou
ld a
rgue
that
the
role
of
the
PDP
pers
pect
ive
is n
ot s
o m
uch
that
it le
ads
us to
a p
ositi
on o
nknowledge as innate
vs
lear
ned
per se.
Rat
her,
its
role
is to
pro
vide
us
with
aco
ncre
te a
nd e
xplic
it fr
amew
ork
in w
hich
to e
xplo
re th
e is
sue
thro
ugh
the
fonn
ulat
ion
of m
odel
s of
the
fact
ors
that
mig
ht b
e in
volv
ed,
Thi
s ar
gum
ent h
as to
be
righ
t up
to a
poi
nt. T
he a
bilit
y to
ext
ract
str
uctu
refr
om a
set
of
inpu
ts a
nd a
pply
it to
nov
el it
ems
clea
rly
depe
nds
on s
hapi
ng f
orce
sim
pose
d by
the
mec
hani
sm th
at e
xtra
cts
the
stru
ctur
e-ex
perie
nces
do
not t
ell
us d
irec
tly h
ow to
gen
eral
ise
in a
nd o
f th
emse
lves
. How
ever
, it i
s no
t at a
ll cl
ear
as y
et ju
st w
hat f
onn
thes
e sh
apin
g fo
rces
rea
lly h
ave
to ta
ke.
It is
cle
ar th
at a
t lea
st s
ome
aspe
cts
of la
ngua
ge s
truc
ture
can
ari
se f
rom
the
shap
ing
forc
es im
pose
d by
rat
her
sim
ple
conn
ectio
nist
net
wor
ks. F
or e
xam
ple,
sim
ple
netw
orks
invo
lvin
g an
inpu
t lay
er, a
hid
den
laye
r an
d an
out
put l
ayer
lear
nre
gula
r m
appi
ngs,
suc
h as
nat
ural
lang
uage
infl
ectio
nal s
yste
ms,
muc
h m
ore
easi
lyth
an th
ey le
arn
arbi
trar
y as
soci
atio
ns (
Plun
kett
& M
arch
man
, 199
1; R
umel
hart
& McClelland
, 198
6). I
f th
e m
achi
nery
of
cogn
ition
is m
ade
up o
f co
nnec
tioni
stne
twor
ks, t
his
alre
ady
sugg
ests
a p
ress
ure
tow
ards
the
regu
lar
map
ping
sch
arac
teri
stic
of
natu
ral l
angu
ages
. Fur
then
nore
, whe
n su
ch n
etw
orks
are
trai
ned
with
wor
d lis
ts th
at in
clud
e m
any
exam
ples
of
a re
gula
r m
appi
ng, b
ut o
nly
a fe
wexceptions, as in the English past tense, they routinely produce over-
regu
lari
satio
n er
rors
, esp
ecia
lly f
or it
ems
of r
elat
ivel
y lo
w f
requ
ency
, thu
ssh
owin
g th
at th
ey, l
ike
youn
g ch
ildre
n le
arni
ng la
ngua
ge, d
o im
pose
str
uctu
reth
emse
lves
as
they
are
lear
ning
. Ind
eed
, Har
e an
d E
lman
(19
92)
have
rec
ently
show
n th
at it
may
be
poss
ible
to a
ccou
nt fo
r th
e st
ruct
ure
of th
e E
nglis
hin
flec
tiona
l sys
tem
, and
inde
ed f
or th
e ev
olut
ion
of th
is s
truc
ture
ove
r tim
e, in
tenn
s of
the
shap
ing
forc
es im
pose
d by
suc
cess
ive
gene
ratio
ns o
f co
nnec
tioni
stne
twor
ks. T
hey
begi
n w
ith a
trai
ning
' cor
pus
refl
ectin
g th
e st
ruct
ure
of th
e sy
stem
at o
ne p
oint
in ti
me,
and
trai
ned
a fi
rst-
gene
ratio
n ne
twor
k w
ith th
is c
orpu
s. T
hey
then
trai
ned
a se
cond
- gen
~ra
tion
netw
ork
with
the
outp
ut o
f th
e fi
rst-
gene
ratio
nne
twor
k. D
ue to
the
regu
lari
satio
n pr
oces
ses
men
tione
d ab
ove,
the
outp
ut o
f th
efi
rst-
gene
ratio
n ne
twor
k w
ill te
nd to
hav
e a
sim
pler
and
less
arb
itrar
y st
ruct
ure
than
its
inpu
t. T
he s
econ
d-ge
nera
tion
netw
ork
furt
her
regu
lari
ses
the
stru
ctur
e,an
d th
en s
erve
s as
the
inpu
t to
a th
ird-
gene
ratio
n ne
twor
k. T
he p
roce
ss c
ontin
ues
over
sev
eral
gen
erat
ions
, and
the
stru
ctur
e of
the
infl
ectio
nal s
yste
m g
radu
ally
evol
ves.
Usi
ng th
is p
roce
dure
, Har
e an
d E
lman
(19
92)
have
bee
n ab
le to
cap
ture
seve
ral a
spec
ts o
f th
e ev
olut
ion
of th
e E
nglis
h pa
st- t
ense
sys
tem
. The
y ha
ve b
een
able
to s
how
that
if th
ey s
tart
the
firs
t net
wor
k of
f w
ith th
e in
flec
tiona
l sys
tem
char
acte
rist
ic o
f E
arly
Mid
dle
Eng
lish,
in w
hich
ther
e w
ere
seve
ral v
aria
nts
ofth
e re
gula
r pa
st te
nse ,
the
corp
us g
radu
ally
evo
lves
ove
r ge
nera
tions
to a
sys
tem
like
our
curr
ent s
yste
m, i
n w
hich
onl
y on
e va
riant
of t
he r
egul
ar fo
nn d
omin
ates
.T
hus
we
can
see
the
stru
ctur
e th
at e
mer
ges
as th
e re
sult
of a
pply
ing
and
reap
plyi
ng a
set
of
cons
iste
nt s
hapi
ng f
orce
s-th
ose
appl
ied
by th
e ne
twor
k-to
the
corp
us.
The
re r
emai
ns a
gre
at d
eal o
f deb
ate
abou
t whe
ther
net
wor
ks th
at le
arn
mor
phol
ogy
capt
ure
all o
f th
e de
tails
bot
h of
the
adul
t sta
te a
nd o
f th
e co
urse
of
acqu
isiti
on (
Pink
er &
Pri
nce,
198
8; P
inke
r, 1
991)
, but
ther
e is
no
disp
utin
g th
efa
ct th
at n
etw
orks
do
impo
se s
truc
ture
. The
ext
ent t
o w
hich
they
do,
inte
rest
ingl
y,is
a m
atte
r of
thei
r pa
ram
eter
s. T
hus,
for
exa
mpl
e , it
is v
ery
wid
ely
know
n in
Stru
ctur
e Im
pose
d by
the
Lea
rner
As
a fi
nal p
oint
, I w
ould
like
to a
ddre
ss o
ne m
ore
kind
of
evid
ence
that
is o
ften
take
n as
sup
port
ive
of a
nat
ivis
t pos
ition
. Thi
s is
evi
denc
e th
at th
e hu
man
min
dis
not
sim
ply
a pa
ssiv
e re
posi
tory
of
expe
rien
ce, b
ut a
ctua
lly im
pose
s st
ruct
ure
on e
xper
ienc
e be
yond
that
dic
tate
d by
the
envi
ronm
ent.
The
exi
sten
ce o
f ov
er-
regu
lari
satio
n er
rors
in c
hild
ren
s us
e of
the
past
tens
e is
one
cas
e in
poi
nt; s
uch
beha
viou
rs h
ave
been
take
n as
indi
catin
g th
at th
e co
gniti
ve s
yste
m is
impo
sing
orde
r on
its
inpu
ts, o
rgan
isin
g th
em in
to a
sys
tem
. In
fact
, the
ver
y fa
ct th
atla
ngua
ge h
as s
ynta
x ha
s of
ten
been
take
n as
evi
denc
e th
at th
ese
orga
nisa
tiona
lpr
inci
ples
are
inna
te. A
fter
all
, lan
guag
e is
a c
reat
ion
of th
e hu
man
min
d, s
o--
the
argu
men
t goe
s-th
e st
ruct
ure
of la
ngua
ge m
ust b
e a
char
acte
rist
ic o
f th
est
ruct
ure
of th
e m
inds
that
use
it. I
f al
l lan
guag
es e
xhib
it ce
rtai
n st
ruct
ural
char
acte
rist
ics,
it w
ould
app
ear
to f
ollo
w th
at th
e sp
ecif
icat
ions
of
wha
t the
sest
ruct
ural
cha
ract
eris
tics
shou
ld b
e m
ust b
e in
nate
as
wel
l.
McC
LE
LL
AN
D4. NATURE AND NURTURE
IN D
EV
EL
OPM
EN
T
the
conn
ectio
nist
res
earc
h co
mm
unity
that
if o
ne w
ants
to p
rodu
ce a
mec
hani
smth
at e
xtra
cts
the
gene
ral s
truc
ture
com
mon
to m
ost o
f th
e ite
ms
in a
trai
ning
set
,ig
nori
ng id
iosy
ncra
tic c
hara
cter
istic
s of
indi
vidu
al e
xem
plar
s, th
en o
ne s
houl
dco
nstr
ain
the
num
ber
of c
onne
ctio
n w
eigh
ts. I
n re
spon
se to
this
, sev
eral
rese
arch
ers
have
use
d th
e m
etho
d of
Wei
gand
, Rum
elha
rt a
nd H
uben
nan
(199
1),
intr
oduc
ing
an e
xtra
tenn
in th
e fu
nctio
n th
at th
e ne
twor
k m
inim
ises
, ove
r an
dab
ove
the
disc
repa
ncy
betw
een
its im
plic
it pr
edic
tions
and
obs
erve
d in
puts
,re
flec
ting
the
num
ber
of n
on-z
ero
conn
ectio
n w
eigh
ts. W
hat h
appe
ns in
lear
ning
depe
nds
on th
e w
eigh
t giv
en to
this
ext
ra te
nn. W
hen
this
cos
t ten
n is
wei
ghte
dhe
avily
, net
wor
ks w
ill b
ecom
e ve
ry le
an, imposing a severe tendency to
regu
lari
se th
eir
inpu
ts; o
n th
e ot
her
hand
, if
the
pres
sure
is m
ild, n
etw
orks
can
be fr
ee to
mem
oris
e th
e de
tails
of t
he tr
aini
ng c
orpu
s, g
reat
ly r
educ
ing
the
syst
emat
icity
of
thei
r ha
ndlin
g of
nov
el f
onns
. The
wei
ght a
ssig
ned
to th
e co
stte
nn is
an
exam
ple
of a
net
wor
k pa
ram
eter
that
mig
ht v
ary
acro
ss d
omai
ns,
perh
aps
set d
iffe
rent
ly in
dif
fere
nt p
arts
of
the
syst
em b
y ge
netic
reg
ulat
ion.
Of
cour
se, i
t will
be
clea
r th
at th
e w
ork
desc
ribe
d to
dat
e fa
lls f
ar s
hort
of
dem
onst
ratin
g th
at th
e fu
ll st
ruct
ure
of n
atur
al la
ngua
ge c
an b
e un
ders
tood
intenns of the in
tera
ctio
ns o
f ne
twor
k le
arni
ng p
roce
sses
with
exp
erie
nce.
Nev
erth
eles
s, it
doe
s se
em c
lear
that
the
POP
appr
oach
off
ers
a ne
w w
ay to
thin
kab
out j
ust w
hat k
ind
of b
uilt-
in c
onst
rain
ts m
ight
be
invo
lved
in m
aint
aini
ng a
ndin
deed
impo
sing
str
uctu
re in
a d
omai
n. R
athe
r th
an th
ink
abou
t dom
ain-
spec
ific
prin
cipl
es, s
peci
fied
in te
nns
of th
e ac
tual
con
tent
of
the
dom
ain
, we
are
enco
urag
ed to
thin
k in
tenn
s of
the
setti
ngs
of th
e pa
ram
eter
s of
ver
y ge
nera
lm
echa
nism
s. O
f co
urse
, nat
ure
does
set
thes
e pa
ram
eter
s, a
nd p
resu
mab
ly s
hedo
es s
o fo
r a
purp
ose.
Ind
eed,
we
can
imag
ine
that
it is
one
of
the
task
s of
nat
ural
sele
ctio
n to
spe
cify
just
suc
h pa
ram
eter
s, p
erha
ps s
epar
atel
y fo
r di
ffer
ent p
arts
of th
e co
gniti
ve s
yste
m, s
o th
at s
ome
part
s w
ill b
e in
clin
ed to
str
uctu
re a
nd e
ven
rest
ruct
ure
thei
r in
puts
and
oth
ers
to m
emor
ise
indi
vidu
al c
ases
.
abou
t lea
rnab
ility
bas
ed o
n th
e dr
awba
cks
of c
lass
ical
ass
ocia
tioni
sm n
eed
to b
ere
-eva
luat
ed. I
hav
e ar
gued
that
the
char
acte
rist
ics
of th
ese
mec
hani
sms
offe
rus
way
s to
und
erst
and
the
fitf
ul c
ours
e of
dev
elop
men
t; th
at th
ey a
llow
us
tofr
ame
expl
icit
alte
rnat
ives
to n
ativ
ist a
ccou
nts
of e
arly
com
pete
nce;
and
that
they
impo
se s
truc
ture
in w
ays
that
cor
resp
ond
to th
e st
ruct
ure
that
lear
ners
impo
se.
The
se d
emon
stra
tions
sug
gest
that
the
prin
cipl
es th
at g
over
n th
e tim
e-co
urse
and
the
outc
ome
of d
evel
opm
ent m
ay b
e bo
th s
omew
hat b
road
er a
nd a
t the
sam
etim
e so
mew
hat m
ore
spec
ific
than
they
ofte
n ap
pear
to b
e in
nat
ivis
t app
roac
hes.
On
the
one
hand
, if
inde
ed g
ener
al p
rinc
iple
s of
pro
cess
ing
and
lear
ning
app
lyac
ross
dom
ains
, the
n th
e ul
timat
e ex
plan
atio
n of
cog
nitiv
e st
ruct
ure
and
itsem
erge
nce
will
be
base
d la
rgel
y on
thes
e ge
nera
l pri
ncip
les.
On
the
othe
r ha
nd,
the
way
s in
whi
ch th
ese
gene
ral p
rinc
iple
s pl
ay th
emse
lves
out
in d
etai
l in
spec
ific
dom
ains
are
obv
ious
ly h
ighl
y va
ried
, and
an
effo
rt to
und
erst
and
wha
tgi
ves
rise
to th
e st
ruct
ure
that
em
erge
s in
any
giv
en d
omai
n w
ill f
orce
a f
urth
ercl
arifi
catio
n of
the
natu
re o
f the
dom
ain
itsel
f, an
d of
the
way
s in
whi
ch it
sst
ruct
ure
inte
ract
s w
ith th
e ge
nera
l pri
ncip
les
to g
ive
rise
to th
e ph
enom
ena
that
we
actu
ally
obs
erve
in b
ehav
iour
. In
this
sen
se, w
e m
ay o
ne d
ay a
chie
ve a
dua
lun
ders
tand
ing,
at o
nce
of th
e ge
nera
l and
of
the
spec
ific
, and
of
the
way
in w
hich
the
spec
ific
ref
lect
s an
d m
odul
ates
the
char
acte
rist
ics
of th
e ge
nera
l pri
ncip
les.
The
ulti
mat
e ev
alua
tion
of th
e ut
ility
of
the
conn
ectio
nist
app
roac
h w
ill, o
fco
urse
, dep
end
on h
ow m
uch
insi
ght t
hey
ultim
atel
y yi
eld
into
dev
elop
men
t. A
tpr
esen
t it i
s no
t at a
ll cl
ear
how
far
con
nect
ioni
st id
eas
abou
t lea
rnin
g an
dre
pres
enta
tion
will
take
us.
For
now
, it s
eem
s cl
ear
that
thes
e id
eas
are
poin
ting
us in
inte
rest
ing
and
usef
ul d
irec
tions
. Whe
ther
, as
rese
arch
con
tinue
s, to
day
conn
ectio
nist
idea
s th
emse
lves
sur
vive
, or
whe
ther
they
lead
inst
ead
to e
ven
mor
epo
wer
ful i
deas
, is
a qu
estio
n w
e m
ust l
eave
to th
e fu
ture
.
The
re is
a g
reat
dea
l mor
e to
s~y
abo
ut th
e po
ssib
le im
plic
atio
ns o
f con
nect
ioni
st
mod
els
for
the
stud
y of
cog
nitiv
e de
velo
pmen
t, an
d th
e w
ork
is ju
st b
egin
ning
.I
hope
that
this
cha
pter
beg
ins
to il
lust
rate
the
reas
ons
why
I e
xpec
t the
app
roac
hto
bec
ome
a m
ajor
foc
us o
f re
sear
ch. T
he m
ain
poin
t of
this
cha
pter
has
sim
ply
been
to s
how
that
con
nect
ioni
st m
odel
s al
low
us
to e
xplo
re in
exp
licit
com
puta
tiona
l mod
els
the
vari
ous
fact
ors
and
forc
es th
at m
ight
be
thou
ght t
osh
ape
deve
lopm
ent,
The
se in
clud
e th
e en
viro
nmen
t, th
e ba
sic
prin
cipl
es o
fpr
oces
sing
and
lear
ning
, and
dom
ain-
spec
ific
arch
itect
ural
and
par
amet
ricva
riat
ions
that
may
sha
pe th
e tim
e-co
urse
and
the
outc
ome
of d
evel
opm
ent.
Ase
cond
them
e ha
s be
en to
arg
ue th
at m
any
of th
e ar
gum
ents
that
hav
e le
d m
any
prom
inen
t the
oris
ts to
fav
our
nativ
ist a
rgum
ents
des
erve
to b
e re
-eva
luat
ed. T
ore
cap
brie
fly,
I h
ave
argu
ed th
at c
onne
ctio
nist
mod
els
of le
arni
ng o
ffer
mor
epo
wer
ful t
ools
than
the
clas
sica
l ass
ocia
tioni
st a
ppro
ach,
so
that
arg
umen
ts
RE
FER
EN
CE
S
AK
NO
WL
ED
GE
ME
NT
S
SUM
MA
RY
AN
D C
ON
CL
USI
ON
ST
he a
rgum
ent p
rese
nted
in th
is c
hapt
er h
as b
een
deve
lope
d ov
er s
ever
al y
ears
, and
sev
eral
colle
ag~e
s an
~ co
llab~
rato
rs h
ave
cont
ribu
ted
in s
ubst
antia
l way
s to
its
deve
lopm
ent.
Iw
ould
m p
artic
ular
hke
to a
ckno
wle
dge
cont
ribut
ions
by
Jeff
Elm
an, G
eoff
Hin
ton,
Jam
es H
oeffn
er, A
nnet
te K
arm
iloff-
Smith
, Yuk
o M
unak
ata,
Ran
dy O
' Rei
lly, K
imPl
unke
tt, D
ave
Rum
elha
n, M
ark
Seid
enbe
rg a
nd R
oben
Sie
gler
. The
mem
bers
of
the
PDP
Gro
up a
t CM
U h
ave
prov
ided
use
ful c
omm
ents
and
fee
dbac
k. T
he w
ork
has
been
supp
oned
by
a C
aree
r D
evel
opm
ent A
war
d (M
H- O
O38
5) a
nd a
Pro
gram
Pro
ject
Gra
nt(M
H-4
7566
) fr
om N
IMH
,
Bai
llarg
eon,
R. (
1987
). O
bjec
i per
man
ence
in 3
. 5-
and
4.5-month-old infants,
Del
'ldop
men
tal
Psyc
holo
gy,
23, 6
55--
664.
Bai
llarg
eon
, R. (
1993
). T
he o
bjec
t con
cept
revi
site
d: N
ew d
irect
ions
in th
e in
vest
igat
ion
of in
fant
sphysical knowledge. In C. Granrud (Ed),
Vis
ual p
erce
ptio
n an
d ('O
~nition in infancy, C
arne
gie
Mel
lon
Sym
posi
a on
Cog
nitio
n. H
illsd
ale,
NJ:
Law
renc
e E
rlba
um A
ssoc
iate
s In
c.
McC
LE
LL
AN
DN
AT
UR
E A
ND
NU
RT
UR
E I
N D
EV
EL
OPM
EN
T
Bai
llarg
eon,
R.,
Gra
ber,
M.,
DeV
os, J
" &
Bla
ck, J
. (19
90).
Why
do
youn
g in
fant
s fa
il to
sea
rch
for hidden objects?
Cog
nitio
n,
36, 2
55-2
84.
Baillargeon, R.
, Spe
lke,
E,S
., &
Was
serm
an, S
. (19
85).
Obj
ect p
erm
anen
ce in
five
-mon
th-o
ldin
fant
s.
Cognition, 20,
191-
208.
Bat
es, E
., &
Elm
an,
L. (1993). Connectionism and the st
udy
of c
hang
e, In
M.J
ohns
on
(Ed.
Bra
in
development and cognition:
read
erpp
. 623
--64
2. O
xfor
d: B
lack
wel
l.C
ase,
R. (
1978
), In
telle
ctua
l dev
elop
men
t fro
m b
irth
to a
dulth
ood:
A n
eo-P
iage
tian
inte
rpre
tatio
n.
In R. Siegler (Ed.
),
Chi
ldre
ns thinking: What develops?,
pp. 3
7-71
. Hill
sdal
e, N
J: L
awre
nce
Erlb
aum
Ass
ocia
tes
Inc.
Dia
mon
d, A
. (19
91).
Neu
rops
ycho
logi
cal i
nsig
hts
into
the
mea
ning
of o
bjec
t con
cept
dev
elop
men
t.
In S, Carey & R. Gelman (Eds),
The epigenesis of mind: Essays on biology and cognition.
pp.
67-1
10. H
illsd
ale,
NJ:
Law
renc
e E
rlba
um A
ssoc
iate
s In
c.E
lman
, J,L. (1990). Finding structure in time, Cognitive Science, i4,
179-
211.
Flav
ell,
J.H, (1963),
The developmental psychology of Jean Piaget.
New
Yor
k: V
an N
ostr
and,
Har
e, M
., &
Elm
an, J
.L. (1992). A connectionist account of English in
flec
tiona
l mor
phol
ogy:
Evidence from language change, In
Pro
ceed
ings
of t
he i4
th A
nnua
l Con
fere
nce
of th
e C
ogni
tive
Science Society,
pp, 2
65-2
70. H
illsd
ale,
NJ:
Law
renc
e E
rlba
um A
ssoc
iate
s In
c.H
into
n, G
.E, (
1986
). L
earn
ing
dist
ribut
ed representations of concepts, In P
roce
edin
gs o
f the
Eig
hth
Annual Conference of the Cognitive Science Society,
pp. 1
-12.
Hill
sdal
e, N
J: L
awre
nce
Erl
baum
Ass
ocia
tes
Inc.
Inhelder, B., & Piaget, J. (1958).
The
gro
wth
of
logi
cal t
hink
ing
from
chi
ldho
od to
ado
lesc
ence
.N
ew Y
ork:
Bas
ic B
ooks
,K
anni
loff
-Smith, A, (1986), From meta-
proc
esse
s to
con
scio
us a
cces
s: E
vide
nce
from
chi
ldre
nmetalinguistic and repair data.
Cog
nitio
n.
23, 9
5-14
7.
Kan
nilo
ff-S
mith
, A. (
1991
). B
eyon
d m
odul
arity
: Inn
ate
cons
trai
nts
and
deve
lopm
enta
l cha
nge.
In S. Carey & R. Gelman (Eds),
The
epi
gene
sis
of m
ind:
Ess
ays
on b
iolo
gy a
nd c
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