machine perception

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Scots Philosophical Association

University of St Andrews

Machine PerceptionAuthor(s): Margaret A. BodenSource: The Philosophical Quarterly, Vol. 19, No. 74 (Jan., 1969), pp. 33-45Published by: on behalf of the and theOxford University Press Scots Philosophical Association

University of St. AndrewsStable URL: http://www.jstor.org/stable/2218186Accessed: 28-07-2015 02:31 UTC

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2/14

33

MACHINE PERCEPTION

BY

MARGARET

A.

BODEN

I

Could

a

machine

perceive

?

It seems to be

currently

fashionable

for

philosophers, implicitly

or

explicitly,

to

deny

the

possibility

of a

percipient

machine.

Sometimes

they

produce

a verbal

argument,

to the effect

that

we

should

never

call one and the same individual both

percipient

and a

machine,

thus

echoing Wittgenstein's

remark in the

Investigations:

360. But a machine surely cannot think -Is that an empirical

statement

?

No. We

only

say

of a human

being

and

what

is

like

one that

it

thinks

....

This

type

of

argument

I

find

unpersuasive.

Even

if one

accepts,

which

I

should be

reluctant to

do,

that there

is

some

basic

contradiction in

com-

bining

the terms

'percipient'

and 'machine

',

this contradiction

surely

arises because our

language

was formed in a culture

ignorant

of

advanced

technology-in

this

case,

logical absurdity may

be

a

poor

test

of

empirical

possibility. Similarly,

I am

unconvinced

by parallel arguments claiming

that no machine whatever

could,

without

contradiction,

be

said

to

use

language,

to assert

propositions,

to

answer

questions

and so on. I

shall not

discuss this

type

of

argument

further-nor

shall

I

discuss those

arguments

which

rest

upon

the notion of some

private,

inner

process

essential to

per-

ception

but

denied to

machines.

Sometimes,

however,

arguments

are

produced

claiming

to show

that in

principle

no

machine could

perceive,

because a

percipient

being

must be

able to do some

specific

things

which

a machine

just

could not do.

This

type of argument is partly conceptual, for it requires at least a rudimentary

analysis

of

the

concept

of

perception,

and

partly

empirical,

in that it

makes

claims about

what machines can

and cannot do-in

terms,

that

is,

of

possible

outputs,

not

merely

of what are to

be

approved

as

justifiable

descriptions

of

those

outputs.

Moreover,

it

is

said,

if

we

apply psychological

words

to

the behaviour of

machines,

we confer

courtesy-titles,

and such

courtesy

is

excessive

and

dangerous,

for

machines are in

principle

so far

removed

from

the

really

important

and

interesting

human

capabilities

that

psychologists

are

wasting

their time if

they try

to

produce explanations

based on

machine

research.

An

example

of such an

argument

is to

be

found in a recent

article

by

Mr. Alan

Gauld,1

and

I

shall

refer to some

points

in Mr.

Gauld's

paper

as

examples

of the

point

of view

I

wish to

rebut.

What, then,

is

it

to

perceive

an

object

? Is there

anything

intrinsic to

the

concept

of

perception

which

could

not,

in

principle,

be

predicated

of a

machine ? Discrimination is

certainly

a

necessary part

of

percipient

be-

haviour.

The Modern

Times

machine dealt

with

Charlie

Chaplin

in

exactly

1"

Could

a Machine Perceive ?

",

Brit. J.

Phil.

Sc.,

Vol.

XVII,

Part

I,

May

1966.


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3/14

34

MARGARET

A. BODEN

the same

way

as with its

more conventional

raw

materials,

and there is

thus no

reason whatever for

saying

that it

could

perceive any

difference

between them.

A

creature which

is to discriminate

between one class of

things

and

another,

for instance

between

ducks and

rabbits,

must be

able

to

recognize

a

given

animal as a duck.

But,

like

lions,

all ducks are

different,

and

thus

some form of

stimulus-generalization

must take

place;

any

machine

which

may

be said to

perceive

must

have some

way

of

unifying

differing

inputs

so

as

to

give equivalent

outputs,

it

must be able to

recognize

different

ducks

as

ducks,

different

rabbits as rabbits. As

we shall

see,

Mr.

Gauld

argues

that

no such

power

could be built into a

machine.

But

discriminatory

behaviour,

while an essential

part

of the

concept

of

perception,

is

not

enough:

a rather more

modern

machine,

which

consistently

threw

Chaplin

off the conveyor belt, would not on that account be said to perceive him.

Mr.

Gauld

states

the

basic

problem

as " how we come to be able

to

recognize

a

chair

as

a

chair,

a tomato

as a

tomato,

and so forth

".2

In this he follows

all those

philosophers

who have

analysed

perception

in terms of

judgment,

of

concepts,

of

knowledge

that. He refers us to a

rat,

no

doubt

imaginary,

who

is

trained to

eat

pound-notes

whenever he comes across them. This

is

certainly

discriminatory

behaviour,

but not sufficient

reason for

saying

that

the

rat

perceives

pound-notes,

if

this

is

to mean that

he

perceives

them

as

pound-notes.

For

this,

the

note

has also to be seen as

something

of

value,

as

something

relevant to

exchange,

bribery

and

corruption,

as

legal

tender

in a

complex

monetary system,

all

of which

high-level

notions are

foreign

to rats-as

also to children

and idiots. In

order to decide

whether

a

creature

can

perceive

an

X as an

X

we have to ask

whether the creature

possesses

not

only

the

concept

of

X,

but a matrix of

related

concepts. Seeing

a tomato

as

a tomato

involves

more than

seeing

it

as

edible,

for one

must see it

as a

tomato

and not

as an

apple,

as a

vegetable

which was once

alive,

and

so

on;

it

follows

that no

animal other

than

man

could see a tomato as a

tomato,

since verbal behaviour would be required to express some of these distinctions.

Granted

that

animals

cannot be

taught

anything

which will

pass

as a

respectable

analogue

of

language:

what about

machines ?

Here Mr.

Gauld

argues

that

machine

analogues

of

language

are not

respectable

enough

to

allow

for

perception,

since no machine could ever

extrapolate

word-labels

to

new,

physically

dissimilar

instances of

a

class,

and a

fortiori

could

not

build

up

its own

concepts

by recognizing

the

unity

in

various

parts

of the

environment

and

abstracting

rules

representing

"

common

properties

"

in

the

various

physical

situations said to be instances of

the

concept.

There

is no

physical

feature common to all instances of "

exchange

" or "

game

",

and

even

seeing

something

as a tomato

requires

the

possession

of a number

of

similarly high-level

concepts.

This freedom from

specific

features of

the

physical

environment

seems to

be

what

is

meant

by

the

expression

'high-

level

concepts',

and

I

shall

discuss

the

argument

that no machine could

ever

possess

such

concepts

in the

next

section.

O2p.

cit.,

p.

45.




4/14

MACHINE

PERCEPTION

35

II

In

specifying

what he

means

by

'machine'

Mr.

Gauld

refers us to

a

concept

which

is

commonly

used

in the

literature: that

of

a

finite-state

machine

(which Turing,

in his

paper

Computing

Machinery

and

Intelligence,

called a discrete-state

machine).

It

is

possible

to

regard

any

machine

as a

finite-state

machine, i.e.,

a

system

which

must

at

any

moment

be in one

out

of a finite number

of

possible

states,

and

where there

are

rules which

specify

how

its

various

possible

states are to

succeed

one another.

The

rules

may

be

probabilistic,

and

may

even

include a

few

randomizing

operations,

but

in

general

it

is

possible

to

specify

the

state

of and the

input

to

such a

system

and

to

apply

these

rules so as

to

generate

the

succeeding

state

(which

may

or

may

not function

as the

next

input).

Inputs

may

be

internally

or

exter-

nally generated, and may be arbitrary with respect to the present state of

the

system.

To the

extent that

inputs

are

internally

generated,

the

system

as a whole

is autonomous

with

respect

to the

environment.

Thus

a

matrix

linking possible

states in

terms of the

rules

can

in

principle

be drawn

up;

this

is known as a

machine-table,

and

any

such matrix

can be

represented

in a

digital computer.

Thus

any

finite-state

machine

(which

class

includes

at

least some

living things)

can

be embodied

in a

digital computer.

Can

we

embody concepts

in such

a

machine,

so that

discriminatory

behaviour

can

be classified as

perception,

the

object

being

seen as

an

instance

of

the

concept

corresponding

to the word-label

applied

by

the

machine ?

Mr.

Gauld

admits that

in

principle

we

could

observe Jones's

behaviour

expressing

his

concept

of

"

game

"

and

build

in

each

instance

of

Jones's

behaviour

in terms of machine-state

and

machine-input.

The result would

be a

complex

hotch-potch

of

rules,

a

straggly

matrix

drawn

up

by

enumera-

tion of

instances of

Jones's

behaviour.

Mr.

Gauld

says

that

any person

of

moderate

sophistication

would

be able

to

see that

the rules

belonged

to-

gether,

possessed

a

certain

unity.

But

in

what,

he

asks,

could

this

unity

consist ? " Certainly not in physical similarities among the external situa-

tions and

among

the

bodily

states

to which

the rules

refer."3

It is

only

because

we

already

have the

concept

of

game

that

we

can

recognize

all

these

rules as

pertaining

to

games;

and

no

new

game, physically

unlike

any

that

had

gone

before,

could be

recognized

as

a

game

by

such

a machine

-whereas

a human

being

can do

this,

and

parents

and

anthropologists

commonly

do.

In

sum,

no

"

high-level

"

concept

(indeed,

no

concept

at

all)

can

be

expressed

in or

acquired

by

learning-as

a

machine

might

-a

set

of

rules about

how

to react

in each

of a

given

series

of

physical

situations.

"

The

concepts

may

in

some

sense be created

out of such rules

;

but

they

also

transcend

and

unify

them."4

It is assumed

that no

machine

could

generate

its

own

rules for

responding

to the

physical

similarities in

its

environment,

nor

extrapolate

any

rules

written

into

its

programme

by

us. It

would

seem

to follow

that

no

machine

30p.

cit.,

p.

53.

4lbid.,

p.

54.




5/14

36

MARGARET

A. BODEN

could

identify

ducks

or rabbits as members of two

classes,

because

it

would

not be

capable

of the

stimulus-generalization

required

to

recognize differing

individuals as

being

of one and the same

type.

Since

we cannot

specify

precisely

in

advance the various clusters of

physical

characteristics which

as

input-state

should invite the

output

"rabbit

",

we cannot draw

up

a

machine-table for this

task,

and hence

it is

not a task which could be

per-

formed

by

a machine.

Still

less,

on this

view,

could

a

machine

be

expected

to

cope

with

ambiguous

figures

such

as

duck-rabbits. Mr.

Gauld's

view

of

machine-behaviour as thus limited

and

inflexible is

linked

with his view

that finite-state

systems-but

not human

behaviour-are amenable to

mechanical

explanation,

explanation

which could

be

expressed

in

terms of

a

machine-table,

whereby

the

occurrence of

a

given

state is shown to

depend

upon the prior occurrence of other states. This complaint about the rigidity

and narrowness

of machine behaviour

may

seem

plausible

in view of the

nature of

many existing

programmes,

but

it

can be

countered

by

some of

the more

recently

developed programmes,

and

certainly

cannot be

deduced

from the

concept

of

a finite-state

system.

A finite-state

system

is

one in

which

each state

is

determined

by

the

preceding

state,

even

if

the determination

is

by way

of a

randomizing

operator-thus

in

principle

a machine-table

exists

which

will

fully

describe

the succession

of states of

the

system

in

various conditions. But this

is

not to

say

that we

actually

could write the machine-table for

any given

machine,

still less

that

we

could do so before the machine was built and

functioning

so that we could foresee

every

detail

of

its

behaviour.

The

machine-table

can be

guaranteed

only

as a

conceptual

device,

as an extra-

polation

from the basic

postulate

of

determinism as

applied

to

the

physical

states

of

the

machine,

from the

assumption

that

the mechanism works in

accordance

with

known

physical

laws. In most actual

cases the

complete

machine-table

will exist

for

us

only

in the sense in which

the

complete

story of the cosmos existed for Laplace. We may choose to define 'state of

the

system

in

molar,

or

behavioural,

terms,

speaking

justifiably

of

"

one

and the same

"

output

or

initial

state

in cases where the

molecular,

or

mechan-

ical,

specifications

would

be

different.

This will mean

that,

while

a

complete

mechanical

explanation

is

in

principle

always

possible,

we

may

not be able

to

give

it,

and the

terminology

we find it

most convenient to use

may

not

be fitted to reflect

the

level of

detail such an

explanation

would

require.

Unless

one is

prepared

to

deny

that

the

brain

and associated

bodily

functions

are

subject

to familiar

types

of natural

laws

(which

leaves

open

the

possi-

bility of randomness arising in some, specifiable, conditions), then one must

regard

the brain as

(part

of)

a

finite-state

mechanism. If

one is

then

to

deny

that human

behaviour can

be

generated by

such a

system-or,

in

a

sense,

explained

in terms of

it-one must

recognize

that one

is

denying

the

postulate

that our

behaviour

is in some

sense

fully

dependent

on

our

bodies,

on

a series

of

events

which

could in

principle-be

described

by

a

biologically

competent super-Laplace.

Despite

his

strange

remark

about

transcendence




6/14

MACHINE PERCEPTION

37

which I

quoted

earlier,

I

hesitate

to

ascribe

such a

denial

to Mr.

Gauld,

for

I doubt

whether his

psychologist's suspicion

of

the

physiologist

goes quite

this far.

Perhaps

he

merely

means that the

psychologist

uses a

language

con-

sisting

of

organizational

or behavioural

terms,

terms which

commonly

provide explanations,

and

which

cannot be reduced to

physiological

con-

cepts.

However,

the

case

is

parallel

when we consider

machines,

for if we

wish to

explain

the

behaviour

of a

computer

we can do so in

either

of two

ways:

we

can refer to

its

mechanism or

we

can

refer to

its

programme.

These two

types

of

explanation

are not reducible to one

another,

although

the instantiation of

any programme

in

a

particular

case is of course

always

wholly

dependent upon

the detailed

mechanism of the material

object,

the

machine. If we were to give a complete description of the structure and

history

of the

machine,

in

terms of

its individual

components

and the

physical

inputs

it

receives,

there

is a sense

in

which

we should have described

everything

that

was

there,

every

causal factor

contributing

to

its

behaviour.

This is the account

which the

Laplacean

engineer

could,

in

principle,

give

us,

and

we

could

use this means to

explain

the

behaviour;

given

a

certain

output

we

could

list the various

changes

in

the

components

involved

in

producing

it. If

the

machine behaves

in an

unexpected

fashion,

for

instance

if it makes

a

mistake such

as

giving

the

wrong

label to

an

apparently

un-

ambiguous

stimulus-figure,

or

failing

to solve a mathematical

problem

of a

type

which

usually

presents

it

with no

difficulty,

then

we

may explain

such

behaviour

by

opening

the machine and

literally

finding

a

spanner

in the

works,

an

unusual

connection

of

wires,

or a short

circuit. In

principle

this

type

of

explanation

will

always

be

in

order,

for

there will

always

be

some

physical

basis for the

strange

behaviour.

However,

in

many

cases a

quite

different

type

of

explanation

will

be

in

order

also,

will

indeed be more

illuminating,

and this

will involve

reference to the

programme.

The

concepts

of mechanism and programme are independent

of one

another,

and

a

person

can understand

the nature

of a

given programme

and

even

criticize

or write

one

without

any knowledge

of

electronic

hardware.

A

programme

is written

before

it is

instantiated

in

any particular

machine,

and

it

may

be built into

machines

differing

greatly

in their

basic

mechanism.

This is so because a

programme

is a

logical

or

behavioural

as

opposed

to

a

physical

concept;

it

is

expressed

in

terms of notions

such as

equal,

greater

than,

average,

and

operations

such

as

search,

compare, test, repeat, increase,

delete

. . .

and the

more

sophisticated

programmes

can

be

described

in terms

of

concepts

such

as goal, sub-goal, means to an end, heuristic selectionof criteria or operators,

etc. In the

example

mentioned

before,

of the

machine's

apparently

making

a

mistake,

we should

be wise to look

carefully

at the

logical

structure

or

plan

of

the

behaviour

and

to see whether

similar

mistakes

were

made in

similar

problem-situations.

This

investigation

might suggest,

for

instance,

that

a

certain

instruction

in the

programme

had been

wrongly

expressed

by

tlhe

programmer

so that there

was

a

systematic

mistake

in situations where




7/14

38

MARGARET A.

BODEN

that

instruction was

called

upon;

one

example

of

this

would

be an

infinite

loop

in the

programme

under certain

(logical)

conditions-that

is,

a

rule

or

series

of rules in

the

programme

would

be

applied

recursively,

so

that the

solution

of

the

problem

would

be

blocked

in a

characteristic

fashion.

These

hypotheses,

drawn from observation of the behaviour of the

machine,

could

then

be checked

by referring directly

to the

programme,

if

this

were available

in the

form

of

a

print-out

from the

machine;

if

the

machine

were

one which

can

modify

its own

programme,

but made no record

of such

modifications

which

could be

printed

out

directly,

then

we

might

have to

be content

with

behavioural

confirmation of our

hypothesis

alone. To be

sure,

if

there

is

an infinite

loop

in

a

programme

then

it will

be

true to

say,

for

instance,

that such-and-such

a

circuit

tends to

be

continually

activated under such-

and-such conditions-but even if we are able to provide a description at

this

level it will

not enable

us to see

the

logical

or

behavioural structure of

the

fault,

nor

will

it

necessarily

suggest

immediately

how the fault can be

put

right.

Both

ways

of

describing

what

is

going

on are

useful,

and

each

carries

with

it its

own form of

explanation.

If we

consider

the

programmes

developed

in

an

attempt

to

simulate

pattern-recognition,

we find that

many

of

them do

have

the

failings

which

Mr.

Gauld

mentions. But

there

are some

which

are

a

good

deal

more

sophis-

ticated,

and which cannot be so

easily

faulted.

One

of

these

is

a

programme

developed

by

Uhr & Vossler,5 which will enable a machine to learn to

recog-

nize

line-drawings, including

letters,

numbers and

cartoon-figures.

Each

input-pattern

is

assessed in terms

of

a number

of

criteria,

or

"

operators

",

and

these

determine

the

label chosen to

classify

the

pattern.

Basically

the

operators

used reflect

physical

characteristics

of the

pattern,

such as

the

average

number

and/or

position

of certain

shapes,

but

the

first-level

charac-

teristics

can be combined

with

one another

in

various

ways

to

form

more

sophisticated,

high-level,

characteristics. Thus the

recognition

is

always

based on physical

features of the

patterns,

but cannot

necessarily be reduced

to a

straightforward

list of

physical

characteristics

easily

expressed

in

simple

geometrical

terms,

such

as

'three-sided rectilinear

figure

'.

The

concept

of

"

physical

similarity

"

is

by

no

means

a

clear one-one can

programme

a

computer

to deal

with

topological

relationships,

and even to

recognize

geometrical

and

topological

analogies

between

diagrams

of the

type

com-

monly

used

in

intelligence

tests,

but

I

suspect

that

many

people

who

think

of

machines as

limited

to

the

recognition

of mere

physical

similarities

might

not think

of

including

such

relationships

in this

category.

In

the

Uhr

&

Vossler programme verbal definition of any given operator, even a first-

level

operator,

may

be

difficult,

and

a

fortiori

it

may

be

impossible

to

deduce

the

exact

nature of the

operators

used

from an

examination

of

the

labels

actually applied

to

the

various

input-patterns.

Such

classificatory

behaviour

5Uhr,

L.,

and

Vossler, C.,

"

A

pattern

recognition program

that

generates,

evaluates,

and

adjusts

its

own

operators

",

in

"

Teleological

Mechanisms

",

Annals

New York

Acad.

Sc.,

50: 189

(1961),

pp.

555-569.

Reprinted

in E.

A.

Feigenbaum

& J.

Feldman

(eds.), Computers

and

Thought

(New

York,

1963),

pp.

251-268.




8/14

MACHINE PERCEPTION

39

may

indeed

seem to

"

transcend

"

the

physical

characteristics,

while

being

based

upon

them.

The

operators

used

may

be,

but

need

not

be,

pre-programmed; they

can be

initially

generated

at random

by

the

machine,

and then selected

on

the basis of their

success,

and can be

weighted differentially

so that those

most useful in

discriminating

between different

patterns

are relied

on

more

heavily

thereafter. The machine will

also

tend

to select

those

operators

which are

particularly

useful in

cases of

difficulty,

where two

patterns

may

be

easily

confused. The

number

of

operators

relied

upon

for

each discrim-

ination

can be

varied,

and

so also

can

the

extent

of

"

memory

"

for

past

examples,

so that the

groups

of

operators

responsible

for

the

application

of

a

given

label

in

different

cases

may

be related

to

one another

by

shifts

in

membership similar to the shifting of criteria which Wittgenstein compared

to

family-resemblances.

Of

course,

there has

to be some

criterion

of successful

labelling

other than

the

labelling

response

itself;

this

may,

and in the

present

programme

does,

come from

the

judgment

of a human

operator

(compare

the

parent

saying

"

Yes,

that's

right

"),

but

there

could be

a

programme

in which

the

consequences

of

wrong labelling

were

such that the

labelling

could

be

retrospectively

marked

as

incorrect,

and

appropriate

adjustments

made.

This

requires

that the

labelling

be made use

of

by

the machine

in

further

tasks,

and

I

shall

return to

this

point

later.

Although

in

many

pattern-recognition

tasks this

programme gives

results which-while im-

pressive-are

inferior

to

those obtained

from

human

subjects,

it

is note-

worthy

that

when tested for

ability

to

recognize

"nonsensical"

doodles,

its

performance

is

significantly

better than that

of

any

of

the human sub-

jects

so

tested.

It

is,

of

course,

in these

cases

that

the effect of the

greater

prior experience

of

the human

subject

is minimized.

This

programme

can

generate

its

own

criteria,

and

evaluate and

adjust

them in

response

to the

particular

features of the

patterns

it

encounters.

In principle, the programme could be improved so as to provide for the

building up

of a matrix of labels

linked

together

both

hierarchically

and in

other

ways,

so that

something

labelled

as "a tomato

"

might

be

linked

not

only

hierarchically

with the

label

'vegetable',

but

also

associatively

with

the label

'Worthing'; similarly,

it

would

not seem too

difficult

to

allow

for the

generation

of

analogical

or

metaphorical

uses,

such as

labelling

a certain man

as

"

a

rabbit

",

either in

virtue of

facial

or of

behavioural

characteristics.

It would

then

be

possible

to

raise such

questions

as whether

two

machines

with differential

learning

experiences

had the

same

concept

of tomato, even though both could apply the label correctly to actual

tomatoes,

or

pictures

of

tomatoes. I do

not

deny

that

it

would

require

a

great

deal

for

us

to

be able

to

say

that

they

had

the same

concept

of

tomato

as

ourselves,

not least

because

this would

require

a

machine

which

could

make

tactile and

chemical

discriminations

as well as visual ones.

However,

to admit that

the

complexity

and

number of discriminations

made

by

the

machine would have

to

be

very

great,

before

one

could

speak

of

the

same




9/14

40

MARGARET

A. BODEN

concept

with

an

easy

conscience,

is not

to

say

that

in

principle

this is

im-

possible

of

achievement.

Insofar

as

perceiving

a tomato

requires

having

a

concept

of

a

tomato,

together

with a network

of

related

concepts,

I

am not

convinced

that

no machine

could be built

with

such

a

property.

III

So far

I

have

argued

that the fact

that

a machine

may

be

regarded

as

a finite

state

system

does not

imply

the sort of behavioural

rigidity

which

would

prevent

it from

attaching

correct labels

to stimulus

inputs

in

various

situations,

even

in cases

where

the new instance

is

physically

very

dissimilar

to those

it

has encountered

so far.

However,

this

is

not to

say

that we

can

straightforwardly apply

the

concept

of

perception

to

any

machine

capable

of attaching the correct6 verbal labels to external objects, for perception

involves

more

than mere discrimination-it

involves the use of

discrimination

in

the

guidance

of

voluntary

action.

We

do not

merely

characterize

or describe

what

is

going

on

by

saying

"He

perceived

the

policeman

",

or

"

He sees

it as

a

policeman

"-we also

explain

differences

in behaviour

:

if

you

want to know

the

time,

ask

a

police-

man,

but

not a wax

dummy

outside Madame

Tussaud's. The

explanation

is

teleological

in

character,

for

perception

is a

purposive

notion

closely

con-

nected

with

that

of instrumental

activity.

The discriminations

are

used

in

the

activity-they

guide

the choice of means to a given end, they direct the

strategy

for

reaching

the

goal

by

picking

out the

appropriate

means

and

sub-goals,

and

rejecting

inappropriate

ones.

It

is

by

means of

perception

that

we

adjust

to the detailed

features of

the environment when we are

performing

complex

tasks-for

to

adjust

our behaviour

in this

way just

is

to

make

the

sorts

of

discrimination,

of

differential

response

to

particular

features

of the

environment,

which we term

perceptual

discrimination.

To

attain certain

goals,

certain

procedures

are

appropriate;

but

if

you

can't

tell a hawk from a handsaw you are likely to find some difficulty in fitting

these

procedures

to

reality.

Your

failure can then

be

explained

in terms of

your

mistaken

perception,

though

the

precise

nature of

that

misperception

may

be inferred

from

the

details

of the fruitless behaviour

itself.

If a creature

reacts

differentially

to various

environments then we

may

say

it

is

sensitive

to

changes

in the

environmental features involved. A

limpet

on

a

rock,

or a

sea-anemone,

may

be sensitive

to

sunrise and

sunset,

or even

to the

shadow

of

a boat

passing

through

the

water,

and this

sensi-

tivity

may

be shown

by changes

in

the

muscular tonus

of

the

organism;

but

to speak of perception here would be out of place. This would require a

fairly complex

background

of

behaviour,

such that

smaller

behavioural

units

of various

types

can be

distinguished

from

one

another,

and

naturally

occur

together

in series

making

up

larger

behavioural

units,

a

description

of which

gives

a

description

of the

activity

of the

organism.

Moreover,

those

cases

of

activity

to which

the

concept

of

perception

is

particularly

8See

p.

44.




10/14

MACHINE PERCEPTION

41

appropriate

are those where the behaviour

is of

such

flexibility

that ob-

stacles

to

the

attainment

of

the

goal

are not

only likely

to

be

overcome,

but

overcome

with

a

certain

economy

of

effort,

such that

different

types

of

obstacle elicit different

types

of

compensatory

behaviour,

so

that

the

goal

is reached as

efficiently

as

possible,

granted

the motor abilities of the

organ-

ism. This

may

be

seen

by

considering

examples

of

complex

behaviour which

may

mislead

us,

such that

we

ascribe

inappropriate perceptions,

and

imply

the

wrong

sort of

explanation.

For

instance,

a robin

defending

his

territory

in

spring

will behave

in

exactly

the same

aggressive

fashion whether

we

confront

him

with

a

male

robin

or with

a

piece

of

red

flannel

waggling

on a

stick.

The

bird's

behaviour

is not

to be

explained

in

terms

of its

goals

and

intentions,

or

its

perceptual

judgments about the relevance or threatening character of certain environ-

mental intruders.

The bird's

behaviour

is

fixed,

it is

determined

by

this

particular

stimulus-sign,

by

a small

part

of

the total

stimulus-array

which

happens-in

normal

circumstances-to

form

part

of a

second,

and

possibly

rival,

robin. In

such

cases,

explanation

in

terms

of

finely

discriminating

perceptions

or

concepts

such

as sexual

rivalry

is

superfluous,

as

explanations

are available

at a

much

lower

level;

this is shown

by

the

nature

and inflexi-

bility

of the

behaviour,

and

does

not

depend upon

our

denying

concepts

or

perceptions

to the animals

in

the

absence of

language.

The

bird's

sensitivity

to a

specific

feature of the environment is

responsible

for the occurrence of

the behaviour

in these

conditions

rather

than

in

others,

but

it

does not

go

on

to make the further discriminations

which

would

lead

to

a cessation or

modification

of

the

activity

so

as

to fit

it

more

appropriately

to the

environ-

ment.

In

this

case,

at

least,

explanation

of

the bird's

behaviour in

terms of

its

perceptions

would

seem to be out of

place.

Moreover,

the

behaviour

is

predictable

from

a

knowledge

of

the environmental conditions

alone,

i.e.,

the season

and

the

presence

or absence of a

particular releasing

stimulus,

and successful prediction does not requirereference to the ongoing behaviour

of the

bird,

it

does not

require

us

to

ascribe

particular

purposes

or

intentions

to this

individual

bird.

In

general,

while movement

may

be

analysed

in

terms of

muscle-twitches,

behaviour

must

be

analysed

into conative

units,

but the

purposes

or

goals

involved

may

be more

properly

ascribed

to the individual

organism

in some

cases

than in

others-that

is,

to the

organism

as

an

individual,

rather

than

as a

member

of the class

of,

e.g.,

robins.

In those

cases

where

such

ascription

is most

appropriate

we

may

speak

of

"voluntary

"

behaviour. In such

cases we cannot predict the behaviour from a knowledge of the environ-

mental situation

alone,

but must

explain

the

occurrence

of this

goal-seeking

behaviour

rather than

any

other

which

lies

within the animal's

repertoire,

by

referring

to

behavioural

patterns

which are not

closely

dependent

on

specific

stimuli

from

outside,

and which

may

differ in different

individuals.

This

element

of autonomous

selection

requires

that

there

be

a

behavioural

repertoire

from which

to

select-i.e.,

that the

organism

is

capable

of

seeking

various different

goals

in

various

different

manners.

The

more

varied the




11/14

42

MARGARRET

A. BODEN

tasks

which

a

creature

may

perform,

the more room there

is

for

the

ascrip-

tion of voluntariness

to its

activities.

But

this

ascription

will

only

be

in

order

when the

behaviour

is

flexible in

the

sense

already

described-i.e.,

when

different

obstacles

to the

attainment of

the

goal

are

encountered

and

coped

with

appropriately,

so that the

goal

is reached

notwithstanding

the

difficulties

presented

by

the

environment.

Naturally,

in some cases the

goal

will

not

be

reached,

but the

more

the behaviour shows

changes

describ-

able as

attempts

to reach the

goal,

the more

readily may

we

speak

of

volun-

tary

behaviour. Some

degree

of

persistence

is therefore

required

for

volun-

tary

action,

but

if

inappropriate

behaviour

is

persisted

in

then

we

may

not

regard

the

behaviour

as

voluntary,

particularly

if

we

believe

the

organism

to be

capable

in other conditions

of

making

the discriminations

required

to

show that and how the behaviour is inappropriate-for example, compare

the

persistence

of

a

very young

child

trying

to

fit a

piece

into a

jigsaw-puzzle

inappropriately

with that

of

a

panic-stricken

man

trying

to

get

out

of a

room

by

the

locked

and

solid

door,

instead

of

breaking

out

through

the window.

Stereotyped

and

rigid

behaviour,

which

is

unresponsive

to

unusual

features

of the

environment,

such that

the

organism

may

easily

be

cheated

of

the

goal,

may

be

seemingly

very

complex-as

in

the

courtship

and

nest-building

behaviour

of

some birds-but

is

clearly

different from behaviour which

is

guided by

perception

of

the

environment

and which

varies

according

to

such discriminations so as to maximize the

probability

of

reaching

the

goal.

This

is a

conceptual

matter : I

am

claiming

that what we

call

perceptual

discrimination

will

be

required

if

an animal

is

to

learn new

skills,

or

is to

be able to

adjust

his

behaviour

in

conditions

of

difficulty;

I am

not

claiming

that all

motor

activity

under the control of the

organism

is

directed

merely

by

a continuous

series

of

perceptual

or

kinaesthetic

sensations-indeed,

there is

good

experimental

evidence

against

such a view.

The

greater

the

degree

of

autonomy

of the

organism

vis-a-vis

specific

features of the environ-

ment, and the more the organization of behaviour differs across individuals,

the

more

will

we be

ready

to

speak

of

the

goals

or

purposes of

the creature

itself,

and of

its

voluntary activity

in

seeking

those

goals.

These features of

flexibility

and

autonomy

of

behaviour, which,

as

we

have

seen,

require

discriminatory ability

on the

part

of the

organism,

are

not in

principle

denied

to

machines. There

are

already

phototropic

machines

which

will

avoid

physical

obstacles

in their

path,

maze-running

programmes

which

will

learn

short-cuts,

and

problem-solving

programmes

which

will

select

the

most

appropriate

from

a

number of heuristics when

they

are

searching

for a solution. To be

sure,

existing programmes

have

nothing

approaching

sufficient

complexity

for us to

be

tempted

to

distinguish

be-

tween their

voluntary

and

involuntary

behaviour;

outputs

are

very

closely

tied

to

specific inputs,

and while

a

machine

may

be able to select

for

itself

the

way

in

which

it

will

attempt

to solve a

problem,

and

may

be

able

to

apply

criteria of

difficulty

which

will

prevent

its

attempts

at solution from

going

on

indefinitely,

it

will

not be able

to

ignore

the

problem

as

a

problem

because

it is

irrelevant to the

general

pattern

of

interests of the

individual




12/14

MACHINE

PERCEPTION

43

machine.

A

problem

may

be

put temporarily

into

a

"

queue

",

and

queue-

jumping

may

be allowed for

on the

basis

of

certain

criteria,

but that is

only

the

rudimentary

beginning

of

anything

which

could

plausibly

be called

free

choice

of

problems

to be tackled because

they

are relevant to

the

general

purposes

of the machine. Connected with this

point

is the fact

that,

so

far,

programmes

are

very

narrowly

conceived

so as to

cope

with a

restricted

range

of

problems

only-in

other

words,

the

behavioural

repertoire

of

existing

machines

is small.

Even

a

programme

specifically designed

to

give

a

com-

paratively

wide

range

of

behaviour,

such

as

Newell,

Simon

& Shaw's

"

Gen-

eral

Problem Solver

"7

(which

uses

the

abstract notions

of

means-end

analysis

and

heuristics,

and which

can

cope

with

a

wide

variety

of

formal

problems),

is

in

fact restricted

to

a small

number of

operations

of

certain

logical types, and does not produce anything which one would want to call

voluntary

behaviour.

Moreover,

even

the

General

Problem

Solver

is

based

on

serial

processing

and thus

is

unsuitable for

the

generation

of

behaviour

which

can

be described

as

directed

to several

goals

at

once,

and where the

informational

input (compare

:

perceptual

processes) may

be

more available

to or

necessary

for one

goal

than for another. If we

are to simulate such

behaviour

as

helping

a

child

with his

algebra

while

making pastry

for

a

dinner-party,

stopping

the

vegetables

from

boiling

over and

periodically

brushing

the hair from our

eyes,

we must

rely

on some form of

parallel

processing.

Further,

existing

machines do not

go

in for instrumental

activity

-that

is,

they

do

not mould

the

environment itself

so as

to make

it

more

suitable for the

pursuing

of

their own

purposes;

such

moulding

of

the

environment

clearly

would

require

the sorts

of

discriminations

we

term

perceptual,

and would involve

motor

activity

on the

part

of

the machine.

It is

true

that

there are

programmes,

for instance some

of

those

designed

to

simulate

pattern-recognition,

which

will

take

a

record

from the

environ-

ment,

and

then mould

that

record

so

as

to make

it

more amenable to

treat-

ment-one simple example would be the deletion of any blank borders of

the

original

record

so as

to

make

all

the

patterns

dealt with of

much

the

same overall

size.

However,

this

change

does

not

feed back onto the en-

vironment

but

is

restricted

to the machine's internal

behaviour,

and

there

is

no need

for

a continual series

of

discriminations

of

and

adjustments

to

the

environment

such

as

would

constitute

percipient activity.

But

it

does

not seem

to

be

in

principle impossible

to

build

machines whose motor

activity

would

be

guided

in

this

way.

A machine which

could

recognize

tomatoes

and

pictures

of tomatoes

and

which could

link the

label'

tomato

'

with

the

labels 'edible ',

'living'

and so on,

might

also be able to

classify

a tomato

as

something

soft

and

squashy

on the basis of

its

own motor

activity

of

squashing

some.

And

this

might

result

in

a classification of

a

tomato

as

something

suitable

to

be

thrown

at

politicians

making

speeches,

which

7Newell, A.,

Shaw,

J.

C.,

and

Simon,

H.

A.,

"

Report

on a

general

problem-solving

Program

",

in

Proc.

Int.

Conf.

Information

Processing,

1959

(Unesco).

See

also Newell

&

Simon,

"GPS-A

program

that simulates

human

thought

",

in Lernende

Automation

(H.

Billing,

ed.)

(repr.

in

Feigenbaum

&

Feldman

(eds.), Computers

and

Thought).




13/14

44

MARGARET

A.

BODEN

classification

might

be acted

on

by

the

machine

itself when

confronted

with,

say,

Harold

Wilson.

Why

not ?8

Percipient

activity

involves the

possibility

of

misperception,

as

opposed

to

mere

failure

to

discriminate

at

all,

and the occurrence of

a

particular

misperception

may

be seen from the behaviour of the

organism-a dog

might

attack or

try

to mate with

a

child's

toy

dog,

and

this

could

surely

be

explained

in terms of

misperception,

particularly

if the

dog

soon modified

his

inappropriate

behaviour

on closer

acquaintance

with the

toy.

A

language-

user can

tell us more

directly

about his

perceptions

by

using

verbal

labels

or

concepts,

and

as Mr.

Gauld

points

out

we

not

only say

such

things

as

"

He

sees

the

policeman

",

but "He

sees

it as a

policeman

". If

every

stimulus were

always responded

to in

exactly

the

same

way,

then we

should

have no room for the notion of seeing as. There has to be a possibility of

alternative

categorization

and

of

mistake. The

point

of

saying

"He

sees

it

as

an

X

"

is

largely

to

distinguish

the

situation

in

question

from that where

the

stimulus remains

the

same,

but

we

say

"He sees

it

as a

Y

".

And

this

is a

distinction

made

in

order

to

explain

differences of behaviour

in

the two

cases.

It is

worth

remarking

that a certain

concept

was

applied

because

it

is

in

principle

possible

that another

concept

might

have been

applied,

and

this

would

have made

some difference

to behaviour.

When

a

stimulus

provides

conflicting

or

ambiguous

cues then different

perceptions

may

be

equally

possible;

a

percipient

being may have to

cope

not only with ducks,

and with

rabbits,

but

also with duck-rabbits.

Is

there

any

reason to think

that a machine could

never be

built with such

a

feature ?

Clearly

not;

a

given

stimulus could

lead with

equal probability

to

two

different

outputs

when

presented

in

isolation,

though

the

probability

of

one

output

rather

than

the

other could

be raised

by

contextual factors

such as the nature of

the

preceding

stimuli-a

succession of

non-ambiguous

ducks could

swing

the

response

to the

ambiguous

duck-rabbit

in

the

duck-direction.

Assess-

ment of the correctnessof a discrimination must involve reference to the

interests

of

the

perceiver-thus,

the machine

might correctly classify

ducks

and

rabbits

separately

when

its

general

purpose

or

task

was

defined

in

terms

of

stocking

a

farm-pond,

and

might correctly classify

them

together

when

its

task was defined

in

terms

of

planning

a

vegetarian

menu.

The

existence

of a

variety

of

possible

internal

representations

of the

environment,

together

with the autonomous

selection

of

goals,

provide

a

basis

for the

ascription

of

intentionality

to machines. Insofar

as the

machine's

behaviour

is

guided

by

its own model of the

environment,

which

model

will

involve specificationsof certain objects as means to certain ends, and certain

sub-goals

as

steps

to

further

goals,

the

overall behaviour

will

be describable

in

intentional terms.

Thus the machine's behaviour

may

be

explained

in

terms of

a

perception

or

model

which

is in

fact

mistaken or

misleading,

as

for instance

if it

labelled

a

rabbit

as a

duck

and

then lassoed

it

and threw

8An

experiment

which

is

relevant

here showed that

if

one first

trains

a child to

push

a

button

in

response

to

a

red

light,

and

then

teaches

him to

call

a

series

of

red,

orange

and

yellow lights

by

the

same

nonsense-syllable,

then his

motor

response

be-

comes

generalized

to

all

these

lights.

W.

O.

Shepard,

Child

Devt.

1956,

27,

173-178.




14/14

MACHINE PERCEPTION 45

it

into

a

pond.

And

in

this

case we could

say

in one

sense

that the machine

perceived,

and reacted

to

the

rabbit,

yet

we

could

not

say

that

it

perceived

it

as a rabbit.

Again,

if

we were asked to

say

what

the machine

was

doing

(or

if

it

were asked

to

report

on

this

itself),

it

would

not follow from the

truth of 'It is

preparing

to lasso a duck ' that 'It is

preparing

to lasso a

bird

of the

family

Anatidae '.

Certain

types

of

behaviour would

suggest

the

existence

of

particular

models

of

(compare

:

beliefs

about)

the

actual

nature

of

the

environmental

situation

and

the

strategies appropriate

for

seeking

certain

goals.

A mistaken

assumption

about the overall

goal

being

pursued

by

the machine could lead

us to a mistaken

hypothesis

as to

the

nature

of

the

machine's information about and models

of the

environment,

just

as

we

may

be

misled in our

ascriptions

of

beliefs to

a man if

we are

wrong

about

his general intentions or desires.

IV

To sum

up:

I

have

argued

that,

from the fact that machines

may

be

regarded

as

finite-state

systems,

we cannot

infer

that

their

discriminatory

abilities

must be so

narrowly

restricted

to

precisely specifiable

features

of

the

physical

stimulus that

they

could

never

carry

out the sorts

of

stimulus-

generalization

required

for the correct use

of

verbal

labels.

Nor

is

there

any

reason

to doubt

that

they

could build

up

systems

of labels

related

in

various

ways,

for instance

hierarchically

and

associatively,

as

our

concepts

are

related

to each other.

Moreover,

the more

sophisticated

machines

are

in

principle

open

not

only

to " mechanical

"

explanation,

as is

the brain

itself,

but also

to

the

type

of

explanation

which

we

typically

use

of

human be-

haviour,

involving

reference

to

goals

and intentions. Some

true

propositions

describing

such machines

would

be

intentional

in

character,

as

are

pro-

positions

ascribing

actions

and beliefs

to human

beings; among

such

pro-

positions

would be those

using

the notion of

perceiving

as.

The

concept

of

percep-

tion is closely linked with those of action and intention in such a way that the

fine

adjustments

to

the environment

typical

of

voluntary

actions

are

depen-

dent

upon

discriminations

of the

type

we

term

perceptual.

We

could thus

only

apply

the

predicate 'perceives'

in

its

full sense to

a

machine

if

the

behaviour

of

the machine were

sufficiently

complex,

autonomous

and

flex-

ible

for us to

speak

of

voluntary

as well

as

involuntary

activity.

There

is

no

clear

dividing

line between those

behavioural

repertoires

which would

and

those which would not

quality

for

these

descriptions, though

it

is

clear

that no

existing

programme

offers

any

real

temptation

to use such

language.

But there is no reason in

principle

why

such a machine should not one

day

be

developed: perhaps

a rat could

never see

a tomato

as

a

tomato,

but

a

machine

certainly might.

In

view

of this it is

illegitimate

to condemn

the

psychologist's

attempts

at

computer

simulations of

behaviour

as

inevitably

doomed to

failure. To what

extent

they

will

succeed

in

practice

remains

to

be

seen.

University

of

Sussex.

machine perception

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