Five exaptations in speech: Reducing the arbitrariness of the constraints on language

Why your "head is in the clouds" during thinking: the relationship between cognition and upper space

Higher-order cognition in humans has not generally been viewed as closely entwined with the brain mechanisms mediating more basic perceptual-motor interactions in 3-D space. However, recent findings suggest that perceptual and oculomotor mechanisms that are biased toward the upper field (which disproportionately represents radially distant space) are activated during complex mental operations, ranging from semantic processing to mental arithmetic and memory search. The particularly close affinity with upward conjugate eye deviations--further confirmed in a study of 24 schoolchildren who responded to various mental questions and demands--suggests that active, abstract thinking in humans may have expropriated the focal-extrapersonal brain systems involved in saccadic exploration of the distant environment in other primates.

Dopamine and the origins of human intelligence

A general theory is proposed that attributes the origins of human intelligence to an expansion of dopaminergic systems in human cognition. Dopamine is postulated to be the key neurotransmitter regulating six predominantly left-hemispheric cognitive skills critical to human language and thought: motor planning, working memory, cognitive flexibility, abstract reasoning, temporal analysis/sequencing, and generativity. A dopaminergic expansion during early hominid evolution could have enabled successful chase-hunting in the savannas of sub-Saharan Africa, given the critical role of dopamine in counteracting hyperthermia during endurance activity. In turn, changes in physical activity and diet may have further increased cortical dopamine levels by augmenting tyrosine and its conversion to dopamine in the central nervous system (CNS). By means of the regulatory action of dopamine and other substances, the physiological and dietary changes may have contributed to the vertical elongation of the body, increased brain size, and increased cortical convolutedness that occurred during human evolution. Finally, emphasizing the role of dopamine in human intelligence may offer a new perspective on the advanced cognitive reasoning skills in nonprimate lineages such as cetaceans and avians, whose cortical anatomy differs radically from that of primates.