What is emergence anyway?
bates at CRL.UCSD.EDU
Fri Jul 30 18:46:17 UTC 1999
Talmy is right that it is important to find empirical tests that can
distinguish between grammatical outcomes that have a dedicated
neurocognitive structure and those that have instead emerged
across the course of learning and communication, supported by
neurocognitive mechanisms that have "still kept their day jobs"
(i.e. mechanisms that continue to do non-linguistic work for which
they evolved long before grammar ever appeared). It's not an easy
matter, but there is evidence on the point. Here are just a few
1) Children who have early damage to the putative language organs
in the left hemisphere go on to acquire lexical and grammatical
abilities that are perfectly normal (i.e. they are not aphasic,
although as a group brain-damaged children tend to perform in
the low-normal range, corresponding to an approximate average
loss of 5 - 7 IQ points). Interesting, if these children are
studied after 5 years of age, there seems to be no evidence
whatsoever for differences as a function of early left- vs.
right-hemisphere damage. This conclusion now appears to be
on very solid ground, as several recent and comprehensive
reviews of the literature have shown (by our research group;
by Vargha-Khadem and colleagues; by Eisele and Aram). There
were some inklings in the 1970's that this might not be the
case (e.g. papers by Dennis & Whitaker, Woods & Teuber), but if you go
back and read those carefully you will see that none of these studies
were able to compare left- and right-hemisphere-damaged children
directly. Either they looked only at children with left-hemisphere
damage vs. controls, or they compared LHD and RHD to separate
control groups without ever conducting a direct "head-on" comparison
of the sort that would be required to conclude that one hemisphere
is irreversibly superior to the other. At the very least, this
conclusion suggests that there is no bounded and lateralized "organ"
in the left hemisphere that is innately and irreversibly dedicated
to grammar, and furthermore, parts of the brain that would ordinarily not
be used to mediate grammatical processing can be encouraged to do so, quite
2) Recent neural imaging studies of normal adults have shown that
the putative language areas of the left hemisphere are also involved
in the mediation of non-linguistic processes. For example, studies
from many different laboratories have shown that *ALL* of the
candidate areas in and around the "Broca complex" are active in the
planning and/or covert execution of non-linguistic mouth movements
and/or non-symbolic movements of the hand. In other words, these
areas may be involved in the processing of grammar, but they do a lot
of other things as well, a point that is quite relevant to the
notion of a "dedicated" neuro-cognitive system. Similar findings
are beginning to pile up for the posterior language areas as well.
3) Another outcome of recent imaging studies is the now-widespread
finding that many different parts of the brain are activated during
language tasks, in patterns that vary depending on task demands,
strategies, the expertise and experience of an individual subject.
It may turn out that it makes no more sense to ask "where is language
in the brain" than it does to ask "where is the dance in the dancer?"
To be sure, it is the human brain (and only the human brain) that
does language, but the case is not looking very good right now for
the idea that it does so with a dedicated and well-defined language
organ that has evolved to do language and language alone. -liz bates
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