Professor of Psychology
Why Two Minds Are Better Than One: The Evolution of Words
III. Development of Non-Verbal & Uniquely Human Behavior During an Infant’s First Year
8:00 PM, Monday, November 26, 2012
The evolution of language is an intractable problem if it is assumed (à la Chomsky, 1986) that it emerged full-blown during the ~6,000,000 year period that followed the separation of humans and chimpanzees. It’s intractable because there is no biological basis for postulating so large and complex a mutation or the exaptation of another part of the brain to produce such an immediate effect. Equally serious is our lack of knowledge about the role of non-verbal social skills, also uniquely human, without which language could never have evolved. Bipedalism resulted in a reduction in the size of the pelvis, in particular, a reduction in the size of the birth canal that could no longer accommodate an infant whose adult brain would be > 750-800 cc. Other more recent anatomical changes that were favorable for the evolution of language included the loss of fur, a new method of carrying a newborn infant and a loss of pigmentation in the cornea. Because of the small size of the human pelvis, a newborn human infant differed from other non-human primates in two respects. She was smaller and she also required longer and more intensive interactions with her mother. Prolonged periods of mutual eye gaze facilitated the infant’s acquisition of a dyadic sense of ‘self’ and ‘other’ and joint attention (triadic) to particular objects. Joint attention is a non-verbal cognitive skill that is the foundation of the mechanism for assigning arbitrary names to events and objects, i.e., the evolution of vocabulary. All of these processes are uniquely human.
Herbert Terrace is a Professor of Psychology and Psychiatry at Columbia University. He began teaching at Columbia in 1961 and held visiting positions at the University of Sussex and Oxford University. He has received fellowships from the Guggenheim and Fulbright foundations and from All Souls College at Oxford University. He is the author of Nim (1979) and co-editor (with Janet Metcalfe) of The Missing Link in Cognition (2010) and Agency & Joint Attention (2013). He is currently working on a book on the evolution of language. Since 1961 his research on animal and primate cognition has been funded by NIMH, NSF, and the James McDonald foundations. He has a BA& MA from Cornell University and a PhD from Harvard University. At Columbia, he has served as the Director of Graduate Students in the Psychology Department and has taught courses on the evolution of intelligence, the evolution of language and animal cognition.