harnad@clarity.Princeton.EDU (Stevan Harnad) (12/21/90)
Below is the abstract of a forthcoming target article to appear in Behavioral and Brain Sciences (BBS), an international, interdisciplinary journal that provides Open Peer Commentary on important and controversial current research in the biobehavioral and cognitive sciences. Commentators must be current BBS Associates or nominated by a current BBS Associate. To be considered as a commentator on this article, to suggest other appropriate commentators, or for information about how to become a BBS Associate, please send email to: harnad@clarity.princeton.edu or harnad@pucc.bitnet or write to: BBS, 20 Nassau Street, #240, Princeton NJ 08542 [tel: 609-921-7771] To help us put together a balanced list of commentators, please give some indication of the aspects of the topic on which you would bring your areas of expertise to bear if you are selected as a commentator. ____________________________________________________________________ Language, Tools, and Brain: The development and evolution of hierarchically organized sequential behavior Patricia Marks Greenfield Department of Psychology University of California, UCLA Los Angeles, CA 90024-1563 electronic mail: rygreen@uclasscf.bitnet Abstract: During the first two years of life a common neural substrate (roughly, Broca's area) underlies the hierarchically organized combination of elements in the development of both speech and manual action, including tool use. The neural evidence implicates relatively specific cortical circuitry underlying a grammatical "module." Behavioral and neurodevelopmental data suggest that the modular capacities for language and manipulation are not present at birth but come into being gradually during the third and fourth years of life. An evolutionary homologue of the common neural substrate for language production and manual action during the first two years of human life is hypothesized to have provided a foundation for the evolution of language before the divergence of hominids and the great apes. Support comes from the discovery of a Broca's area analogue in contemporary primates. In addition, chimpanzees have an identical constraint on hierarchical complexity in both tool use and symbol combination. Their performance matches that of the two-year-old child who has not yet developed the differentiated neural circuits for the relatively modularized production of complex grammar and complex manual construction activity.