experience vs. innateness

[Gary Marcus]

Dear Ping (cc: INFO-CHILDES).,

I agree with your claim that the "' innate'-versus-' learned'" dichotomy is
a false one -- but maybe not for the reasons you suggest.  You seem to want
to abandon the distinction because you think that experience is always
implicated, that "interaction between experience and brain development" is
paramount..

You are undoubtedly right that some of the "development of neural tissues
and the like could occur as .. a result of learning experiences."  But how
could it be otherwise?  Surely whenever we learn something the brain
changes in some way.

The real question is whether the brain is importantly shaped in ways that
may not have anything to do with learning.  The Nelson review that you
mentioned does highlight ways in which experience can play an important
role in shaping the brain, but it leaves out part of the story. For
example, Nelson notes that there are critical periods in the development of
binocular depth perception, but doesn't discuss evidence that at least some
important parts of the visual system are organized prior to experience. The
sorts of visual deprivation studies that Nelson appears to have in mind
(e.g., those of  Hubel & Wiesel) have often been misinterpreted. Though
they do show that visual experience plays a role in development, they do
not show that the initial structure is itself a consequence of learning.
Hubel expressed this point clearly in his 1988 book _Eye, Brain and Vision_
(W. H. Freeman) when he wrote that

>  "the nature-nurture question is whether postnatal development depends on
> experience or goes on even after birth according to a built-in program.
> We still are not sure of the answer, but from the relative normality of
> responses at birth, we can conclude that the unresponsiveness of cortical
> cells after deprivation was mainly due to a deterioration of connections
> that had been present birth, not a failure to form because of a lack of
> experience."

An up-to-the-minute (and cleverly-titled) commentary by Mark Hubener and
Tobias Bonhoeffer ("Eyes wide shut", Nature Neuroscience, December 1999,
volume 2, 1043-1044) goes to making the same point: "ocular dominance
columns and orientation maps can develop almost normally without visual
input". Learning must play some role in fine-tuning things, but the basic
structure seems to be available prior to (womb-external) experience.

The empirical evidence is not yet all in, not in the case of language, and
not even in the case of vision, where we have much more straightforward
animal models. But it is clear that biology is full of mechanisms that can
lead to the development of intricately structured machinery, without
requiring learning.

The reason that we should abandon the "nature-versus-nurture" dichotomy is
not because the distinction is fuzzy, but because the "versus" gets things
wrong. It's not an either-or situation -- there can be no learning without
something being innate. And having more innate machinery typically makes
you a better learner, not a weaker one. Sea slugs can learn, a little. But
only a little, because their innate learning machinery is fairly
impoverished. We humans can probably use the same mechanisms (whatever
mechanisms support conditioning have probably been conserved,
evolutionarily speaking), but lucky for us, we seem to have other
innately-given learning mechanisms as well. It's not nature VERSUS nurture,
it's nature AND nurture. Part of development is about learning, but it part
of it is not; we will need to understand both parts in order to have a
complete account.

Best wishes,
Gary


At 01:18 PM 12/1/99 -0500, Ping Li wrote:
>Dear INFO-CHILDES Colleagues,
>
>In light of this list's recent debate on Chomsky's position on sensorimotor
>experience, I'd like to draw your attention to a short article by Charles
>Nelson  "Neural Plasticity and Human Development" (Current Directions in
>Psychological Science, Vol. 8, No. 2, 1999, pp.42-45). In this article,
>Nelson reviews many studies that suggest that the development of neural
>tissues and the like could occur at various points in life as a RESULT of
>learning experiences, and that such development could occur at anatomical,
>neurochemical, or metabolic levels (see also a recent article by my
>colleague C. Kinsley here on the interaction between motherhood, neural
>growth, and learning and memory; Nature, Vol. 402, 137-138, 1999). Nelson
>goes on to argue that the perennial "innate"-versus-"learned" debate in
>developmental psychology is fallacious. Because the nervous system changes
>in response to the demands of the learning environment, especially early in
>life, it is more important, Nelson suggests, for us to examine the
>interaction between experience and brain development (e.g, "the role of
>experience in sculpting neural systems"), than to argue about whether
>aspects of behavior are innate or learned. His example/illustration on face
>recognition (p.44) could easily apply to language. Let me quote the last
>sentence of his article: "In doing so, we may be able to shed some of the
>contentious history that has plagued our discipline for years (e.g., nature
>vs. nurture; innate vs. learned), and embrace new theoretical and empirical
>approaches to human development and brain function."
>
>Sincerely
>
>Ping Li
>***********************************************************************
>Ping Li, Ph.D.                          Email: ping at cogsci.richmond.edu
>Department of Psychology                http://www.richmond.edu/~pli/
>University of Richmond                  Phone: (804) 289-8125 (office)
>Richmond, VA 23173                             (804) 287-6039 (lab)
>U.S.A.                                  Fax:   (804) 289-1905
>***********************************************************************
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