The Role of Vocal Learning in Language. Evolution and Development

Resumo

Vocal learning, one of the subcomponents of language, is put at center stage in this dissertation. The overall hypothesis is that vocal learning lays the foundation for both language evolution (phylogeny) and development (ontogeny), and also high-level cognition. The computational ability found in vocal learning is seen as so enhanced in humans as to yield the kind of recursion that supports language. Empirical evidence on vocal learning in nonhuman animals and humans from behavioral, neuroanatomical, neurophysiological, genetic, and evolutionary fields is suggestive that vocal learning interacts with other cognitive domains at multiple levels. The positive correlation between the hippocampal volume and open-ended vocal production in avian vocal learning species suggests the possible involvement of the hippocampus in vocal learning. The empirical studies of foxp2 in nonhuman animals and humans suggest that foxp2 plays a role in multimodal communication and general cognition. Phylogenetically, Sapiens’ vocal learning abilities are unique among primates. Compared with nonhuman primates, our species possesses stronger and more enhanced connections between the superior temporal cortex and premotor cortex as well as the striatum. In Sapiens, meaning aside, vocal learning as such can explain many features found in speech and its ontogeny such as the specialized auditory mechanism for speech, the preferential attention to speech in newborns, the primacy of vocal imitation among multimodal (visual and auditory) imitative skills and the stages seen in learning to speak. All these characteristics seem to be different and abnormal, albeit to different degrees, in autism. A 25-30% of the autistic population is non/minimally verbal but even the high functioning end of the autistic spectrum presents with abnormalities, such as difficulties in processing speed and an impaired imitative capacity that could be satisfactorily explained if language entered again the definition (and diagnosis) of what autism is, with an special emphasis on vocal learning.