During the first two years of human life a common neural substrate underlies the hierarchical organization of elements in the development of speech as well as the capacity to combine objects manually, including tool use. Subsequent cortical differentiation, beginning at age two, creates distinct, relatively modularized capacities for linguistic grammar and more complex combination of objects. An evolutionary homologue of the neural substrate for language production and manual action is hypothesized to have provided a foundation for the evolution of language (...) before the divergence of the hominids and the great apes. Support comes from the discovery of a Broca's area homologue and related neural circuits 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 neural circuits for complex grammar and complex manual combination of objects. (shrink)

The target article presented a model to stimulate further research and ultimately, a more definitive theory of the ontogeny and phylogeny of hierarchically organized sequential activity. Methodologically, it was intended to stimulate methods for integrating data from different neuropsychological techniques. This response to Givon and Swann focuses on several substantive areas: the role of automaticity in hierarchically organized activity and its neural substrate, the neural ontogeny of planning, cognitive and neural architecture for language functions, and the role of environmental input (...) and interaction in the ontogeny and phylogeny of language, tools, and brain. (shrink)

Ronan Reilly's connectionist simulation both strengthens and advances the theoretical model presented in my 1991 target article, “Language, Tools, and Brain: The Ontogeny and Phylogeny of Hierarchically Organized Sequential Behavior.” Reilly has tested the whole ontogenetic model with a single simulation study explicitly planned for this purpose. His methodology has established that the various components of the theoretical model imply and are compatible with one another. It has also indicated how learning can actualize a pre-established ontogenetic sequence of combining lingusitic (...) symbols and objects. His simulation suggests that the acquisition of linguistic speech may be facilitated by experience with object manipulation, but not vice versa. This hypothesis can and should be empirically tested through research on behavioral development in the two domains. Finally, Reilly has simulated brain architecture, as well as neural learning. His simulation therefore shows how the development of language and object manipulation can result from an interaction between preprogrammed neural architecture (analogous to network architecture) and experience (analogous to the network's training cycles). (shrink)

We propose that some aspects of language evolved to fit the brain, whereas other aspects co-evolved with the brain. Cladistic analysis indicates that common basic structures of both action and grammar arose in phylogeny six million years ago and in ontogeny before age two, with a shared prefrontal neural substrate. In contrast, mirror neurons, found in both humans and monkeys, suggest that the neural basis for intersubjectivity evolved before language. Natural selection acts upon genes controlling the neural substrates of these (...) phenotypic language functions. (shrink)

We approach the issue of holophrasis versus compositionality in the emergence of protolanguage by analyzing the earliest combinatorial constructions in child, bonobo, and chimpanzee: messages consisting of one symbol combined with one gesture. Based on evidence from apes learning an interspecies visual communication system and children acquiring a first language, we conclude that the potential to combine two different kinds of semiotic element — deictic and representational — was fundamental to the protolanguage forming the foundation for the earliest human language. (...) This is a form of compositionality, in that each communicative element stands for a single semantic element. The conclusion that human protolanguage was exclusively holophrastic — containing a proposition in a single word — emerges only if one considers the symbol alone, without taking into account the gesture as a second element comprising the total message. (shrink)