Why do we want to talk? Evolution of neural substrates of emotion and social cognition
Cognitive and emotional processes are now known to be intertwined and thus the limbic system that underlies emotions is important for human brain evolution, including the evolution of circuits supporting language. The neural substrates of limbic functions, like motivation, attention, inhibition, evaluation, detection of emotional stimuli and others have changed over time. Even though no new, added structures are present in the human brain compared to nonhuman primates, evolution tweaks existing structural systems with possible functional implications. Empirical comparative neuroanatomical evidence is presented here in support of such changes in the limbic system, including the amygdala and the orbitofrontal cortex. Given their possible functional significance, these alterations may further enable and enhance human interest and motivation to communicate beyond what is seen in other primates living in complex social groups. The argument here is that even though emotion processing is likely needed for increased social complexity independent of language, the reason why humans want to talk may be related in part to the enhancement of socioemotional processes resulting from the reorganization and rewiring of underlying neural systems some of which are interconnected to the language areas. Neurodevelopmental disorders in humans affecting both language and sociability fuel such arguments.
