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This is a guest post by Herbert Terrace and Michael Studdert-Kennedy, in the form of a response to Marc Hauser, Charles Yang, Robert Berwick, Ian Tattersall, Michael Ryan, Jeffrey Watumull, Noam Chomsky, and Richard C. Lewontin, "The Mystery of Language Evolution", Frontiers of Psychology 2014.

Herb Terrace explains:

At Charles Yang's suggestion, Michael Studdert-Kennedy and I would like to offer a commentary to Language Log in response to an article that appeared in 2014 in Frontiers of Psychology […]. That commentary was peremptorily rejected by Frontiers without explanation.

"Each of us learns his language from other people, through the observable mouthing of words under conspicuously intersubjective circumstances." (Quine, 1960)

In a recent article on the evolution of language, Hauser et al. (2014) concluded that, despite "an explosion of research on this problem," there has been a "poverty" of viable ideas and that, until further evidence is available, our “ . . . understanding of language evolution will remain one of the great mysteries of our species" (p. 1).

The evidence that Hauser et al. (2014) considered is limited, however, reflecting a syntactocentric view of generative linguistics and a failure to consider recent discoveries about the social and cognitive development of a human infant during her first year of life. The latter limitation is a direct consequence of the former.

We do not question the value of the syntactocentric model for descriptive linguistics. But for evolution, it provides no path along which words, the conceptual-intentional primitives of language, which are preconditions for syntax and no less uniquely human, might have developed. Nor does the circular form of their model (Hauser et al., 2002, Figure 2) acknowledge the generally accepted hierarchical structure of language (e.g., Jakobson, 1970) in which syntax must have evolved from semantic and logical relations among words.

Here we call attention to the imperative and declarative functions of words and to the fact that “words” trained in experiments on animal language are strictly imperative. An imperative utterance is uni-directional, its purpose to motivate another being to act, e.g., to provide food, to hug, move out of my territory, etc. In principle, vending machines can be designed to satisfy imperatives. By contrast, declarative communication, implying conversation between a speaker and a listener, was a fundamental step in the evolution of language.

Hauser et al. (2014) seem to be aware that no animal has been trained to communicate declaratively. Discussing Nim Chimpsky, “the chimpanzee that produced the only corpus of data in all animal language studies", they remark that he "produced signs considerably below the expected degree of combinatorial diversity seen in two-year old children…with no understanding of syntactic structure or semantic interpretation". But that observation points to a contradiction in the syntactocentric model of language, a model supposedly uncontaminated by social factors. Any discussion of semantics implies social engagement between a speaker and a listener, in particular, conversation. Indeed, without conversation a child would never learn any words at all, let alone a language.

We are hardly the first to observe that words must have the evolved before syntax (e.g., Bickerton, 1981, 2014; Deacon, 1997; Donald, 1991; Jackendoff, 2002). Nor are we the first to observe the importance of shared reference in the emergence of a child’s first words (Bloom, 2000). We simply call attention to recent research on pre-verbal social mechanisms that contribute to a child’s understanding of a speaker’s referential intent. Hauser et al. (2014) endorse ontogeny as an "important source of evidence for the biological basis of language" (p. 3), but confine their examples to grammar.

Before the recent spurt of research on the social development of infants, little attention was paid to the psychological implications of major anatomical differences between humans and chimpanzees or to the resulting differences in the social evolution of various members of Homo that intervened. A common theme of this research is the fragility of the human infant at birth, forcing extensive postnatal dependency. About 6 mya, long before the size of the Homo brain began to grow, bipedalism was the most important feature distinguishing our ancestors from chimpanzees. One consequence of bipedalism was a decrease in the size of the pelvis, setting a limit on the size of the head that could pass through the birth canal. A human infant’s brain at birth is only ~25% of its adult size; a chimpanzee’s, ~40% (Rosenberg & Trevathan, 1996). Another anatomical change was loss of fur (Wheeler, 1985). Without fur to cling to, a human infant had to be cradled in her mother’s arms where her eyes could readily meet her mother’s.

An infant experiences two significant modes of interaction during her first year. During a dyadic (intersubjective) stage (2-6 months), she is cradled and engages in bouts of face-to-face contact with her mother. These provide opportunities for the infant to detect discrepancies between her and her mother’s emotional states, e.g., when she is happy (or sad) and her mother is not. Beebe (2014), Beebe et al. (2010), Lyons-Ruth (1999), Stern (1985) and Trevarthen and Aitken (2001) hypothesize that infants develop a sense of another’s emotional state from these discrepancies.

During a triadic stage (joint attention), the infant engages in mutual eye gaze with her mother toward particular objects or events and shares attention to them (Scaife & Bruner, 1975; Tomasello, 1995). Behavioral markers of joint attention include the infant’s efforts to direct her mother’s attention by repeatedly shifting her gaze between her mother and an object, and by smiling and cooing when she achieves her goal (Carpenter & Kristen, 2012). Because joint attention combines the mother’s and the infant’s attention to particular objects or events, it allows the infant to infer referential intent from another’s utterances and thereby serves as a foundation for declarative vocabulary (Brooks & Meltzoff, 2008). Evolutionarily, this capacity must have emerged before words.

Although there are sporadic examples of mutual eye gaze in nonhuman primates (Ferrari et al., 2009), it is not sustained with the intensity of mother–infant gaze (Suomi, 2005). Psychologists believe that nonhuman primates use facial and bodily expression to interpret another’s behavior, while infants use them to apprehend another’s mental state (e.g., Tomasello, 2010). Evidence for the perception of other minds in non-human primates does not support the idea that they can coordinate their perceptions of each other’s mind. That is a key difference in the social psychology of human and non-human primates (Terrace, 2013).

Hauser et al. (2014) disregard intersubjectivity and joint attention because the syntactocentric model eschews social factors. But that model doesn’t determine what is and is not relevant for theories of language evolution. There is wide consensus that social factors, in particular those between infant and mother during the infant’s first year precipitate the infant’s first words. As noted by (Hobson, 2002),

Those psychologists who believe that humankind became unique by acquiring language are not altogether wrong. But they are not altogether right, either. Before language, there was something else more basic, in a way more primitive, and with unequalled power in its formative potential that propelled us into language. Something that could evolve in tiny steps, but suddenly gave rise to the thinking processes that revolutionized mental life…That something else was social engagement with each other. The links that can join one person's mind with the mind of someone else— especially, to begin with, emotional links— are the very links that draw us into thought.

Without those links we would have no words, without words, no syntax.

Bibliography

Beebe, B. (2014). My journey in infant research and psychoanalysis: Microanalysis, a social microscope. Psychoanalytic Psychology, 31(1), 4. doi: 10.1037/a0035575

Beebe, B., Jaffe, J., Markese, S., Buck, K. A., Chen, H., Cohen, P., Bahrick, L., Andrew, H., & Feldstein, S. (2010). The origins of 12-month attachment: A microanalysis pf 4-month mother-infant interaction. London, UK: Routledge.

Bickerton, D. (1981). The Roots of Language. Ann Arbor, MIchigan: Karoma Publishers.

Bickerton, D. (2014). More Than Nature Needs: Language, Mind, and Evolution. Cambridge, MA: Harvard University Press.

Bloom, P. (2000). How Children Learn The Meanings of Words. Cambridge: The MIT Press.

Brooks, R., & Meltzoff, A. (2008). Infant gaze following and pointing predict accelerated vocabulary growth through two years of age: a longitudinal, growth curve modeling study. Journal of Child Language, 35(01). doi:10.1017/S030500090700829X

Carpenter, M., & Kristen, L. (2012). Joint Attention, Communication, and Knowing Together in Infancy Joint Attention. Cambridge MA: MIT Press.

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Ferrari, P., Paukner, A., Ionica, C., & Suomi, S. (2009). Reciprocal face-to-face communication between rhesus macaque mothers and their newborn infants. Current Biology, 19, 1768-1772.

Hauser, M., Chomsky, N., & Fitch, W. T. (2002). The faculty of language: What is it, who has it, and how did it evolve? Science, 298, 1569-1579.

Hauser, M., Yang, C., Berwick, R., Tattersall, I., Ryan, M., Watumull, J., Chomsky, N., & Lewontin, R. (2014). The mystery of language evolution. Front Psychol, 5, 1-12.

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Quine, W. V. O. (1960). Word and Object. Cambridge, MA: MIT Press.

Rosenberg, K. R., & Trevathan, W. R. (1996). Bipedalism and human birth: The obstetrical dilemma revisited. Evolutionary Anthropology, 4, 161-168.

Scaife, M., & Bruner, J. (1975). The capacity for joint visual attention in the infant. Nature, 253, 265-266.

Stern, D. N. (1985). The interpersonal world of the infant. New York: Basic Books.

Suomi, S. (2005). Mother-infant attachment, peer relationships, and the development of social networks in rhesus monkeys. Human Development, 48, 67-79.

Terrace, H. (2013). Becoming Human: Why Two Minds are Better than One. Agency and joint attention (pp. 11-48): Oxford University Press.

Tomasello, M. (1995). Joint attention as social cognition. Joint attention: Its origins and role in development, 103-130.

Tomasello, M. (2010). Origins of human communication. Cambridge, Mass.; London: MIT Press.

Trevarthen, C., & Aitken, K. J. (2001). Infant intersubjectivity: Research, theory, clinical applications. Journal of Child Psychology and Psychiatry, 42(1), 3- 48.

Wheeler, P. (1985). The loss of functional body hair in man: the influence of thermal environment, body form and bipedality. Journal of Human Evolution, 14, 23-28.

Preparation of this manuscript was supported by NIH grant MH081153-06.

We thank Beatrice Beebe, Katherine Nelson and Robert Remez for their helpful comments.

Above is a guest post by Herbert Terrace and Michael Studdert-Kennedy.

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