Theoretical Models

[Received wisdom has been that the brain has at birth all the neurons it will ever have. You may remember that from Christopher Reeves' encouragement of neuronal regeneration research after his paralysis. Geidd has been on the forefront of work that has suggested that there are several 'waves' of central nervous system neuronal growth, connective 'foliation,' and dieback in the first 22 years of life. This has very strong implications for child development, particularly in the teen and early adult years, and explains a lot of what linguists already were finding about language acquisition. Its implications in terms of everything from parenting to our legal system are huge. Note that this is a very brief article that does not popularize. For a clear, unbiased view of the issues involved, see Teenage Brain: A work in progress A brief overview of research into brain development during adolescence. 2001. BD

Geidd-School:

Elizabeth Powell. "Studying Functional Differences in the Adolescent Brain may Provide Evidence that the Nervous System is Responsible for Behavior." Serendip. Bryn Mawr. Found July 4, 2005. http://serendip.brynmawr.edu/bb/neuro/neuro04/web1/epowell.html

BOCYF: New Research on Brain Development During the Adolescent Years One of the most remarkable findings in neurobiology over the last decade is the extent of change that can occur in the brain, even in the adult brain, as a function of the physical, social, and intellectual environment. Starting in infancy and continuing into later childhood, there is a period of exuberant synapse growth followed by a period of synaptic “pruning” which is largely completed by puberty. Although, neuroscientists have documented the time line of this synaptic waxing and waning, they are less sure about what it means for changes in children’s and adolescents’ cognitive development, behavior, intelligence, and capacity to learn. Generally, they point to correlations between changes in synaptic density or numbers and observed changes in behavior based on developmental and cognitive psychology.

With new technologies that permit analysis of living brains, the National Institutes of Health has just released exciting new evidence about brain development that continues well into the adolescent years. According to Jay Giedd from the National Institute on Mental Health, advances in computers and mathematics and imaging technology now allow scientists to examine the developing brain as never before. During key periods, the amount of gray matter in some areas can nearly double within as little as a year, followed by a correspondingly drastic loss of tissue as unneeded cells are purged and the brain continues to organize itself. “The brain greatly overproduces the number of brain cells and connections – more than could possibly survive. And then there is a fierce battle amongst these cells and connections and only a very small percentage of them make it. We knew this process occurred in the womb and maybe for the first 19 months of life. But the big surprise was when we actually started following the same child or children with sequential scans as they were growing that there was a second wave of overproduction.” This process of overproduction of individual brain cells which causes a thickening of gray matter continues to increase, peaking around the time of puberty. With puberty, there is a second “pruning’ of cells. This pruning process follows a “use it or loose it’ principle – the cells and connections that are used are going to be the ones that survive; those that aren’t will be the ones that perish. According to Giedd, “the exciting news is that unlike infants whose brain activity is completely determined by their parents and environment, the teens may actually be able to control how their own brains are wired and sculpted.” This new scientific evidence clearly has some important implications for how we think about pre-adolescent and adolescent development. However, according to Elizabeth Sowell, a neuroscientists from the University of California in Los Angeles, “I don’t think anybody has yet figured out a way to make this clinically relevant… still, we’re all hoping that perhaps experts in education or psychology will find ways to make those connections.”

"In the 1960s, when I became a graduate student in linguistics, generative grammar was the hot new topic.  Everyone from philosophers to psychologists to anthropologists to educators to literary theorists was reading about transformational grammar.  But by the late 1970s, the bloom was off the rose, although most linguists didn’t realize it; and by the 1990s, linguistics was arguably far on the periphery of the action in cognitive science.   To some extent, of course, such a decline in fortune was simply a matter of fashion and the arrival of new methodologies such as connectionism and brain imaging.  However, there are deeper reasons for linguistics’ loss of prestige, some historical and some scientific. 

The goal [of Foundations of Language and his work in general. bd] is to integrate linguistics with the other cognitive sciences, not to eliminate the insights achieved by any of them.  To understand language and the brain, we need all the tools we can get.  But everyone will have to give a little in order for the pieces to fit together properly. 

[P]osition: ...the overall program of generative grammar was correct, as was the way this program was intended to fit in with psychology and biology.  However, a basic technical mistake at the heart of the formal implementation, concerning the overall role of syntax in the grammar, led to the theory being unable to make the proper connections both within linguistic theory and with neighboring fields.  Foundations of Language develops an alternative, the parallel architecture, which offers far richer opportunities for integration of the field."

Mesulam M.-Marsel. 1998. "From sensation to cognition." Brain. 121, 1013-1052, found July 2, 2005
PDF http://brain.oxfordjournals.org/cgi/reprint/121/6/1013.

Mesulam does not obviate the traditional perspective that places language primarily in Broca/Wernecke, Geschwind. Instead, he adds to that model an in-out system that focuses a large proportion of linguistic assignment, storage and processing at the sensory and limbic sets. Note that the system is most fully realized in words that prompt to the auditory and visual (A and V in illustration to the right, in which the limbic/paralimbic is displayed in yellow) sets.

" Language is based on a special kind of relationship between sensation and cognition. It allows the formulation and communication of experiences, thoughts and memories through the mediation of arbitrary symbols known as words. The arbitrary associations between word and meaning eventually enter the realm of consolidated knowledge and, as in the case of familiar face and object recognition, become coordinated by transmodal nodes outside the limbic system. The encoding and activation of associations related to language follow principles of organization that are quite analogous to those involved in object recognition and explicit memory."

We examine the question of which aspects of language are uniquely human and uniquely linguistic in light of recent suggestions by Hauser, Chomsky, and Fitch that the only such aspect is syntactic recursion, the rest of language being either specific to humans but not to language (e.g., words and concepts) or not specific to humans (e.g., speech perception). We find the hypothesis problematic. It ignores the many aspects of grammar [grammar here is used as a synonym with language, not as that are not recursive, such as phonology, morphology, case, agreement, and many properties of words. It is inconsistent with the anatomy and neural control of the human vocal tract. And it is weakened by experiments suggesting that speech perception cannot be reduced to primate audition, that word learning cannot be reduced to fact learning, and that at least one gene involved in speech and language was evolutionarily selected in the human lineage but is not specific to recursion. The recursion-only claim, we suggest, is motivated by Chomsky’s recent approach to syntax, the Minimalist Program, which de-emphasizes the same aspects of language. The approach, however, is sufficiently problematic that it cannot be used to support claims about evolution. We contest related arguments that language is not an adaptation, namely that it is “perfect,” nonredundant, unusable in any partial form, and badly designed for communication. The hypothesis that language is a complex adaptation for communication which evolved piecemeal avoids all these problems.

Before we can study language, we are faced with an immediate problem that may strike you as very odd in this day and age. Just what is language?

I discuss three orientations to what the word "thinks" might mean, the mentalist, the behavioral, and the avowal orientations, and explain some variations of each. I urge that mapping out thinking in this way allows us to examine some important issues that escape us with more familiar theories (e.g., mind-brain identity theory, the thesis of intentionality, etc.) and that these have important implications for theorists in the social sciences. I argue that psychological behaviorists often turn out to be philosophical mentalists in disguise, and that a position of philosophical behaviorism is profoundly different from the sort of behaviorism familiar to psychologists.

I shall concentrate on variations of three orientations to what thinking is, and to what words like "thinking," "thinks," and "thought" mean. Each has its merits and its weaknesses.

1. One treats thinking in terms of private mental events, inner processes or occurrences or states.
2. According to a second orientation, what it is to think such-and-such is to have a tendency to behave in a certain range of ways appropriate to the application of that term.
3. And according to a third orientation - a close cousin of the second - the person who thinks such-and-such is the person who is prepared to say that he or she thinks such-and-such.

Is there a language gene (or genes)? We can learn a great deal about how language works by looking at problem areas, and have been doing so at least since Paul Broca. Stromswold's work is with twins, and is highly technical. In short, she has found that certain kinds of specific language impairment (SLI) is heritable.