Language Evolution and Computation Bibliography

Understanding the evolution of language requires evidence regarding origins and processes that led to change. In the last 40 years, there has been an explosion of research on this problem as well as a sense that considerable progress has been made. We argue instead that the richness of ideas is accompanied by a poverty of evidence, with essentially no explanation of how and why our linguistic computations and representations evolved. We show that, to date, (1) studies of nonhuman animals provide virtually no relevant parallels to human linguistic communication, and none to the underlying biological capacity; (2) the fossil and archaeological evidence does not inform our understanding of the computations and representations of our earliest ancestors, leaving details of origins and selective pressure unresolved; (3) our understanding of the genetics of language is so impoverished that there is little hope of connecting genes to linguistic processes any time soon; (4) all modeling attempts have made unfounded assumptions, and have provided no empirical tests, thus leaving any insights into language's origins unverifiable. Based on the current state of evidence, we submit that the most fundamental questions about the origins and evolution of our linguistic capacity remain as mysterious as ever, with considerable uncertainty about the discovery of either relevant or conclusive evidence that can adjudicate among the many open hypotheses. We conclude by presenting some suggestions about possible paths forward.

Set representations are explicitly expressed in natural language. For example, many languages distinguish between sets and subsets (all vs. some), as well as between singular and plural sets (a cat vs. some cats). Three experiments explored the hypothesis that these representations are language specific, and thus absent from the conceptual resources of non-linguistic animals. We found that rhesus monkeys spontaneously discriminate sets based on a conceptual singular-plural distinction. Under conditions that do not elicit comparisons based on approximate magnitudes or one-to-one correspondance, rhesus monkeys distinguished between singular and plural sets (1 vs. 2 and 1 vs. 5), but not between two plural sets (2 vs. 3, 2 vs. 4, and 2 vs. 5). These results suggest that set-relational distinctions are not a privileged part of natural language, and may have evolved in a non-linguistic species to support domain general quantitative computations.

When we transform thoughts into speech, we do something that no other animal ever achieves. Children acquire this ability effortlessly and without being taught, as though discovering how to walk. Damage to specific areas of the brain that are critical to language shows the profound selectivity of cerebral organization, underlining the exquisite biological structure of language and its computational features. Recent advances bring new insights into the neurogenetic basis of language, its development, and evolution, but also reveal deep holes in our understanding.

There is a surprising degree of overlapping structure evident across the languages of the world. One factor leading to cross-linguistic similarities may be constraints on human learning abilities. Linguistic structures that are easier for infants to learn should predominate in human languages. If correct, then (a) human infants should more readily acquire structures that are consistent with the form of natural language, whereas (b) non-human primates patterns of learning should be less tightly linked to the structure of human languages. Prior experiments have not directly compared laboratory-based learning of grammatical strucutures by human infants and non-human primates, especially under comparable testing conditions and with similar materials. Five experiments with 12-month-old human infants and adult cotton-top tamarin monkeys addressed these predictions, employing comparable methods (familiarization-discrimination) and materials. Infants rapidly acquired complex grammatical structures by using statistically predictive patterns, failing to learn structures that lacked such patterns. In contrast, the tamarins only exploited predictive patterns when learning relatively simple grammatical structures. Infant learning abilities may serve both to facilitate natural language acquisition and to impose constraints on the structure of human languages.

This article explores the evolution of language, focusing on insights derived from observations and experiments in animals, guided by current theoretical problems that were inspired by the generative theory of grammar, and carried forward in substantial ways to the present by psycholinguists working on child language acquisition. We suggest that over the past few years, there has been a shift with respect to empirical studies of animals targeting questions of language evolution. In particular, rather than focus exclusively on the ways in which animals communicate, either naturally or by means of artificially acquired symbol systems, more recent work has focused on the underlying computational mechanisms subserving the language faculty and the ability of nonhuman animals to acquire these in some form. This shift in emphasis has brought biologists studying animals in closer contact with linguists studying the formal aspects of language, and has opened the door to a new line of empirical inquiry that we label evolingo. Here we review some of the exciting new findings in the evolingo area, focusing in particular on aspects of semantics and syntax.With respect to semantics, we suggest that some of the apparently distinctive and uniquely linguistic conceptual distinctions may have their origins in nonlinguistic conceptual representations; as one example, we present data on nonhuman primates and their capacity to represent a singular-plural distinction in the absence of language. With respect to syntax, we focus on both statistical and rule-based problems, especially the most recent attempts to explore different layers within the Chomsky hierarchy; here, we discuss work on tamarins and starlings, highlighting differences in the patterns of results as well as differences in methodology that speak to potential issues of learnability. We conclude by highlighting some of the exciting questions that lie ahead, as well as some of the methodological challenges that face both comparative and developmental studies of language evolution.

In this response to Pinker and Jackendoff's critique, we extend our previous framework for discussion of language evolution, clarifying certain distinctions and elaborating on a number of points. In the first half of the paper, we reiterate that profitable research into the biology and evolution of language requires fractionation of ``language'' into component mechanisms and interfaces, a non-trivial endeavor whose results are unlikely to map onto traditional disciplinary boundaries. Our terminological distinction between FLN and FLB is intended to help clarify misunderstandings and aid interdisciplinary rapprochement. By blurring this distinction, Pinker and Jackendoff mischaracterize our hypothesis 3 which concerns only FLN, not ``language'' as a whole. Many of their arguments and examples are thus irrelevant to this hypothesis. Their critique of the minimalist program is for the most part equally irrelevant, because very few of the arguments in our original paper were tied to this program; in an online appendix we detail the deep inaccuracies in their characterization of this program. Concerning evolution, we believe that Pinker and Jackendoff's emphasis on the past adaptive history of the language faculty is misplaced. Such questions are unlikely to be resolved empirically due to a lack of relevant data, and invite speculation rather than research. Preoccupation with the issue has retarded progress in the field by diverting research away from empirical questions, many of which can be addressed with comparative data. Moreover, offering an adaptive hypothesis as an alternative to our hypothesis concerning mechanisms is a logical error, as questions of function are independent of those concerning mechanism. The second half of our paper consists of a detailed response to the specific data discussed by Pinker and Jackendoff. Although many of their examples are irrelevant to our original paper and arguments, we find several areas of substantive disagreement that could be resolved by future empirical research. We conclude that progress in understanding the evolution of language will require much more empirical research, grounded in modern comparative biology, more interdisciplinary collaboration, and much less of the adaptive storytelling and phylogenetic speculation that has traditionally characterized the field.

Empirical data have recently begun to inform debates on the evolutionary origins of music. In this paper we discuss some of our recent findings and related theoretical issues. We claim that theories of the origins of music will be usefully constrained if we can determine which aspects of music perception are innate, and, of those, which are uniquely human and specific to music. Comparative research in nonhuman animals, particularly nonhuman primates, is thus critical to the debate. In this paper we focus on the preferences that characterize most humans' experience of music, testing whether similar preferences exist in nonhuman primates. Our research suggests that many rudimentary acoustic preferences, such as those for consonant over dissonant intervals, may be unique to humans. If these preferences prove to be innate in humans, they may be candidates for music-specific adaptations. To establish whether such preferences are innate in humans, one important avenue for future research will be the collection of data from different cultures. This may be facilitated by studies conducted over the internet.

Understanding developmental and evolutionary aspects of the language faculty requires comparing adult languages users' abilities with those of non-verbal subjects, such as babies and non-human animals. Classically, comparative work in this area has relied on the rich theoretical frameworks developed by linguists in the generative grammar tradition. However, the great variety of generative theories and the fact that they are models of language specifically makes it difficult to know what to test in animals and children lacking the expressive abilities of normal, mature adults. We suggest that this problem can be mitigated by tapping equally rich, but more formal mathematical approaches to language.

We propose a theoretical framework for exploring the evolution of the music faculty from a comparative perspective. This framework addresses questions of phylogeny, adaptive function, innate biases and perceptual mechanisms. We argue that comparative studies can make two unique contributions to investigations of the origins of music. First, musical exposure can be controlled and manipulated to an extent not possible in humans. Second, any features of music perception found in nonhuman animals must not be part of an adaptation for music, and must rather be side effects of more general features of perception or cognition. We review studies that use animal research to target specific aspects of music perception (such as octave generalization), as well as studies that investigate more general and shared systems of the mind/brain that may be relevant to music (such as rhythm perception and emotional encoding). Finally, we suggest several directions for future work, following the lead of comparative studies on the language faculty.

From a biologist's perspective, language has its own particular design features. It is present in virtually all humans, appears to be mediated by dedicated neural circuitry, exhibits a characteristic pattern of development, and is grounded in a suite of constraints that can be ...

We argue that an understanding of the faculty of language requires substantial interdisciplinary cooperation. We suggest how current developments in linguistics can be pro.tably wedded to work in evolutionary biology, anthropology, psychology, and neuroscience. We submit that a distinction should be made between the faculty of language in the broad sense (FLB)and in the narrow sense (FLN). FLB includes a sensory-motor system, a conceptual-intentional system, and the computational mechanisms for recursion, providing the capacity to generate an in.nite range of expressions from a finite set of elements. We hypothesize that FLN only includes recursion and is the only uniquely human component of the faculty of language. We further argue that FLN may have evolved for reasons other than language, hence comparative studies might look for evidence of such computations outside of the domain of communication (for example, number, navigation, and social relations).

Language is an apparent miracle. Children master it with exceptional ease, while simultaneously struggling to walk, hold a fork, and recognize that others have thoughts and emotions that differ from their own. They perform, with near perfection, mental computation and generalizations about language which are virtually impossible for state of the art computers. They grasp the tree-like phrase structure of language even though their parents have never taught them, and most probably couldn't even if they wanted to (such properties of language are not the stuff of school education). And children babble on about the present, past, and future, creating imaginary worlds that no one but they can see.

Humans, but no other animal, make meaningful use of spoken language. What is unclear, however, is whether this capacity depends on a unique constellation of perceptual and neurobiological mechanisms or whether a subset of such mechanisms is shared with other organisms. To explore this problem, parallel experiments were conducted on human newborns and cotton-top tamarin monkeys to assess their ability to discriminate unfamiliar languages. A habituation-dishabituation procedure was used to show that human newborns and tamarins can discriminate sentences from Dutch and Japanese but not if the sentences are played backward. Moreover, the cues for discrimination are not present in backward speech. This suggests that the human newborns' tuning to certain properties of speech relies on general processes of the primate auditory system.

Bound to become a classic and to stimulate debate and research, The Evolution of Communication looks at species in their natural environments as a way to begin to understand what the real units of analysis of communicating systems are, using arguments about design and function to illuminate both the origin and subsequent evolution of each system. It lights the way for a research program that seriously addresses the problem of how communication systems, including language, have been designed over the course of evolution.

Table of Contents

1 Synopsis of the Argument
2 The Evolution of Communication: Historical Overview
3 Conceptual Issues in the Study of Communication
4 Neurobiological Design and Communication
5 Ontogenetic Design and Communication
6 Adaptive Design and Communication
7 Psychological Design and Communication
8 Comparative Communication: Future Directions