Author Info: Thomas A. Farmer, Cornell University – email: taf22@cornell.edu
Title: Cognitive Constraints Also Matter
Cognitive constraints on the evolution of language are inevitable. Accordingly, the focus of this presentation will be to consider the manner in which working memory capacity, a cognitive system relatively overlooked in the language evolution literature, may have contributed to the evolution of human language. More specifically, this presentation aims to illustrate that seemingly qualitative differences in language capability between humans and non-human primates may be reduced, in part, to cross-species quantitative differences in the capacity for working memory. Although it is generally assumed that non-human primates have some capacity for symbol learning, their symbol concatenation ability is largely deficient. Savage-Rumbaugh et al. (1998) attribute this “syntactic” deficiency, in part, to a lack of working memory capacity.
Baddeley, Gathercole, and Papango (1998) argue that working memory capacity plays a strong role in language learning. Specifically, these authors assert that the phonological loop exists largely as a mechanism that facilitates the learning of new words. The phonological loop temporarily stores incoming sounds while additional sound information is processed, and this temporary sound storehouse facilitates a more permanent retention of the words (typically more than one sound) that comprise a language. The authors also implicate the phonological loop in the acquisition of syntax; maintaining multiple words in the phonological loop affords humans the ability to extract syntactic structures from the available linguistic input. 
Based on the work of Savage-Rumbaugh et al., it does appear plausible that the lack of syntactic ability in non-human primates may be due, in part, to the lack of a modality-specific short-term memory storehouse large enough to facilitate symbol concatenation processes. 
Moreover, Conway and Christiansen (2001) review an extensive body of literature regarding the non-human primate capacity for sequential, statistical, and hierarchical learning. In all three categories, non-human primates seem to possess some capability; however, in all three cases, humans substantially outperform them. The differences are most marked in relation to hierarchical learning; non-human primates closely related to humans seem to have notable difficulty learning, or spontaneously engaging in, hierarchical action. Hierarchical learning is an imperative aspect of language acquisition. Syntax is not linear, but proceeds in the hierarchical concatenation of phrasal components. This lack of hierarchical learning capability provides further evidence in support of the importance of working memory in explaining the differential language abilities of humans and non-human primates. The ability to maintain language-relevant information while processing additional information is critical to the subsequent concatenation of hierarchical phrases. 
	Literature reviews in the areas of working memory and statistical learning clearly illustrate that 1) both are important for language use, especially in regard to syntax, and that 2) non-human primates are largely lacking in both of these cognitive capacities. Moreover, it seems quite plausible that the lack of working memory capacity hinders substantial hierarchical learning in non-human primates. It can be inferred, then, that the emergence of modern language could not have occurred until the neurological structures underlying the working memory system were appropriately developed. Indeed, the evolution of the neural substrates underlying the working memory system will be discussed, as well as further implications for language evolution research. Although examining working memory, and its influence on hierarchical learning, may not completely answer the “when” and “why” questions of the language evolution puzzle, considering it as crucial to the evolution of modern language seems unavoidable given existing evidence

						References

Baddeley, A., Gathercole, S., & Papango, C. (1998). The phonological loop as a language 	learning device. Psychological Review, 105(1), 158-173. 
Conway, C. M., & Christiansen, M. H. (2001). Sequential learning in non-human
 primates. Trends in Cognitive Sciences, 5, 539-546.
Savage-Rumbaugh, S., Stuart, S. G., & Taylor, T. J. (1998). Apes, language, and the human 
mind. New York: Oxford University Press.
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