the importance of the nativist–empiricist debate: thinking about primitives without primitive...
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CHILD DEVELOPMENT PERSPECTIVES
The Importance of the Nativist–Empiricist Debate:Thinking About Primitives Without Primitive
Thinking
Barbara Landau
Johns Hopkins University
ABSTRACT—J. P. Spencer et al. (2009) are intent on dis-
mantling the nativist–empiricist debate and they offer
three main supporting arguments. It is argued here that
these arguments are simply orthogonal to the authors’
main goal. More importantly, it is argued that even the
most radical empiricist must embrace some set of primi-
tives as the basis for learning; in some cases, rich primi-
tives may actually be the learning mechanism. The
nativist–empiricist debate is crucial to a healthy dialogue
that allows us to think about how learning and devel-
opment occur, and is therefore vital to our scientific
progress.
KEYWORDS—nativism; empiricism; dead reckoning; lan-
guage; navigation
Spencer et al. (2009) are intent on dismantling the nativist–
empiricist debate, and they frame their arguments as follows.
First, they argue that ‘‘development is often a nonobvious process
that does not easily conform to our intuitions or rational expecta-
tions’’ (p. 79). Second, they argue that the fact of evolution ‘‘does
not remove the need to explain developmental process’’ (p. 80).
Third, they argue that developmentalists must be held to the
‘‘highest of scientific standards’’ because the study of develop-
The author would like to thank Lisa Feigenson, Justin Halberda,Steven Gross, and members of the Language and Cognition Lab andthe Cognitive Development Lab, who all took the time to read theSpencer et al. paper and discuss with me the issues raised therein.
Correspondence concerning this article should be addressed toBarbara Landau, Johns Hopkins University, 231 Krieger Hall,3400 N. Charles St., Baltimore, MD 21218; e-mail: [email protected].
ª 2009, Copyright the Author(s)Journal Compilation ª 2009, Society for Research in Child Development
Volume 3, Number
ment is extraordinarily complex. They offer a wide range of
empirical phenomena illustrating that development is complex
and that human capacities change as a consequence of interac-
tion between the organism and its environment.
Their three points are surely correct, but they are simply
orthogonal to the authors’ main plea: that developmental scien-
tists no longer engage in the nativist–empiricist debate. This
debate is important precisely because it helps us frame answers
to questions about development.
Part of the problem is Spencer et al.’s apparent misunderstand-
ing of the modern nativist position. First, this position does not
embrace the idea that development is simple; it is the very fact of
its complexity that drives the nativist to try to understand what
kinds of rich structures might be capable of supporting the mas-
sive changes that occur over development. Examples abound:
Modern studies of language have long sought to understand how
hearing one’s native language results in learning that language
despite radical differences in experience (Landau & Gleitman,
1985). Modern studies of numerical cognition seek to understand
how knowledge of number changes from a system common to many
species to the one shown by humans alone (Feigenson, Dehaene,
& Spelke, 2004). Modern studies of the development of spatial
representation seek to understand how humans (and other species)
represent location, how these representations are transformed over
one’s own movement, and how these transformed representations
support inferences about one’s current location (Wang & Spelke,
2002). Each of these examples requires that we understand the
basic building blocks of a system, and how these might change
over development, as bodies grow, as minds and brains mature, as
the world of interaction expands.
Second, the nativist may consider the evolutionary contribu-
tion as part of the story of how these building blocks—rather
than others—might have become available to the organism, but
this position does not entail that development itself does not
matter. Our capacity for mental rotation likely embodies abstract
2, Pages 88–90
The Importance of the Nativist–Empiricist Debate 89
geometrical principles that have evolved to reflect principles of
the world in which we have evolved (Shepard, 2001). Still, the
developmentalist wants to understand how this capacity sharpens
over development. Third, surely every developmental scien-
tist—whatever his or her theoretical persuasion—would agree
that we should be held to the highest scientific standards: Our
theories should be coherent and as well articulated as possible,
our empirical tests should be designed to test key principles of
the theories, and our interpretation of empirical results should
extend and enhance those theories.
Spencer et al. particularly worry about positing primitives for
developmental systems. They seem to believe that because their
position emphasizes change, they do not have to specify their
own building blocks. But they do—every theory must start with
primitives. If these are not specified, then we cannot specify the
mechanisms of change, as those changes will operate on the
primitive building blocks. The examples that Spencer et al. offer
to support their arguments are meant to emphasize the detailed
nature of change, but they do not offer theories of either what the
building blocks are, or of how change happens. To do so, they
would need to first specify what the basic building blocks of their
theory should be: the elements of sensations, as proposed by
classical empiricists such as Locke and Hume? Distributed pat-
terns of retinal input, or more abstract structures available to
vision, such as reference systems? Conceptual units such as
nouns and verbs, as assumed by many modern developmental
psycholinguists? After specifying the building blocks, they would
have to explain how experience and interaction with the world
change those building blocks and their organization—either by
growing them, reorganizing them, or eliminating them. One can-
not ignore building blocks just because there is change to
explain. Rather, one cannot explain change unless one also spec-
ifies the nature of the building blocks.
In fact, one of the principal domains of study explored by
Spencer et al. is a perfect example of how a theory of an innate
mechanism can help explain learning. This is the domain of
navigation and the mechanism of dead reckoning. Spencer
et al. worry about the proposal that dead reckoning is an innate
capacity whose appearance does not rely on prior relevant
experience. They object that some of the evidence
offered—navigation of alpine geese along novel and lengthy
routes—is not convincing because the geese were not tested at
birth. They further object that infants’ dead reckoning emerges
‘‘gradually after the onset of independent locomotion.’’ If they
mean that dead reckoning becomes more precise as the infant
moves around the world, then yes, but it is the presence of the
dead reckoning mechanism that would allow the infant to cali-
brate over development at all.
It is instructive to read the discussion by Gallistel, Brown,
Carey, Gelman, and Keil (1991) on the nature of the dead-
reckoning mechanism. The most widely cited example of
dead reckoning is the case of the foraging ant, who leaves
its nest and navigates over long distances to find food. After
Child Development Perspectives, V
finding food, it turns and runs in a direct line to the home
nest without benefit of odor trails or the sight or scent of
the nest. To do this, the ant must compute the rough direc-
tion and distance of its nest at every moment along its out-
ward-bound path. There is powerful evidence for this. If the
ant is displaced in midsearch, it will take the course that
would have been correct if it had not been displaced, show-
ing that the computation of distance and direction from the
nest is guiding its (now erroneous) path. The mechanism
underlying the ant’s behavior is path integration—the inte-
gration of direction and distance over time—so that the ant
has a running record of its current position relative to home.
It is a mechanism by which the ant can learn where it is
at the end of its route relative to the home nest, and can
use that representation to produce the right path to get
home each time. This mechanism can sensibly be considered
a building block for the ant: an innate mechanism that can
be used by the ant to learn where he is moment-to-moment,
by measuring distance and direction on the ant’s very first
foray.
Importantly, because this is a learning mechanism, it can be
calibrated, as recently reported by Wittlinger, Wehner, and
Wolf (2006): Desert ants whose legs are artificially lengthened
(hence take longer strides) overestimate distances, whereas
those whose legs are shortened (taking shorter strides) underes-
timate distances. Thus, the mechanism is capable of change
depending on leg length. Equally important, when these altered
ants now start out from their nest on a new journey, they travel
to the source of food and return to their home nest with their
usual accuracy—they immediately adjust to their new leg
length and alter their travel vector accordingly. Thus, the mech-
anism expects change. The application to human infants is clear:
The path integration mechanism is a starting point—a building
block—that enables learning of one’s current location. It can
be calibrated with growth and experience (longer leg length,
walking faster, learning to run, etc.). Learning one’s current
location at time t relative to other locations can support repre-
sentations of a unified cognitive map that permits inferences
about new routes. Our understanding of the dead reckoning
mechanism is still incomplete, but the evidence suggests that it
is a hard-wired part of the ant’s nervous system as well as that
of human infants. The mechanism is a building block that both
embraces and explains learning because it IS the mechanism of
learning.
Spencer et al.’s objections to the idea that dead reckoning is
an innate mechanism seem to hinge on their idea that experience
counts. Well, experience does count. Just not the way they envi-
sion: Experience is what feeds the mechanism to produce repre-
sentations of current location, and experience is what tunes the
mechanism to keep it robust over development. But experience
does not cause the mechanism.
This conclusion will likely not sit well with Spencer et al., for
reasons aptly put by Gallistel et al. (1991, p. 27):
olume 3, Number 2, Pages 88–90
90 Barbara Landau
Here (with dead reckoning) we have a spectacular example of a
dedicated specialized learning mechanism that makes possible the
moment-to-moment acquisition of positional information. People’s
reaction to the claim that this is a learning mechanism is also reve-
latory of the (we believe erroneous) conceptual framework within
which most of us think about learning . . . when one draws the con-
clusion that . . . the learning mechanism is the mechanism that
integrates velocity with respect to time, they balk . . . the way out
of this paradox is to recognize that learning is, generally speaking,
the acquisition of particular mechanisms dedicated to the acquisi-
tion of particular kinds of representations—in this case, a represen-
tation of the animal’s momentary spatial position.
Even the strongest empiricist position—say, that of Locke or
Hume—requires a starting point to explain development. If
Spencer et al. want to suggest that there are no starting points
at all, they will find themselves quite disadvantaged in trying
to develop a coherent theory of any domain. If they want to
argue that the building blocks offered by nativists are the
wrong ones, then fair enough. In that case, they can propose
different building blocks and accompanying mechanisms, and
see how well these account in detail for a given set of empiri-
cal phenomena, thereby providing exciting new contributions to
the ongoing debate. But none of this requires that we abandon
the nativist–empiricist dialogue. Rather, it embraces that
dialogue, and invites us to think deeply about the origins and
Child Development Perspectives, V
nature of human understanding—issues pondered throughout
history by the greatest minds in philosophy, psychology, and
cognitive science.
REFERENCES
Feigenson, L., Dehaene, S., & Spelke, E. S. (2004). Core systems ofnumber. Trends in Cognitive Sciences, 8(7), 307–314.
Gallistel, C. R., Brown, A., Carey, S., Gelman, R., & Keil, F. (1991)Lessons from animal learning for the study of cognitivedevelopment. In S. Carey & R. Gelman (Eds.), The epigenesis ofmind: Essays on biology and cognition (pp. 3–36). Hillsdale, NJ:Erlbaum.
Landau, B., & Gleitman, L. R. (1985) Language and experience:Evidence from the blind child. Cambridge, MA: Harvard UniversityPress.
Shepard, R. (2001). Perceptual-cognitive universals as reflections of theworld. Behavioral and Brain Sciences, 24, 581–601.
Spencer, J. P., Blumberg, M. S., McMurray, B., Robinson, S. R.,Samuelson, L. K., & Tomblin, J. B. (2009). Short arms and talkingeggs: Why we should no longer abide the nativist–empiricistdebate. Child Development Perspectives, 3, 79–87.
Wang, R., & Spelke, E. (2002). Human spatial representation: Insightsfrom animals. Trends in Cognitive Science, 6(9), 376–382.
Wittlinger, M., Wehner, R., & Wolf, H. (2006). The ant odometer:Stepping on stilts and stumps. Science, 312, 1965–1967.
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