Dendrophilia and the Evolution of Human Cognition
Understanding of the neural mechanisms involved in human cognition, and their evolutionary history, requires comparisons between humans and nonhuman animals. Ideally, such comparisons are grounded in an explicit, computational framework encompassing both formal and neural components. I review work comparing cognitive computation in humans with nonhuman primates, other mammals, and birds carried out in the last decades to explore the neural basis and evolutionary origins of human cognition. This comparative research suggests the dendrophilia hypothesis, which proposes that humans are unusual in our ability to process complex hierarchical structures across multiple cognitive domains (language, music, etc.). These hierarchical abilities require computational power at the supra-regular level (above finite state), which support processing of the abstract tree structures needed for language, music and other complex cognition. However, dendrophilia makes heavy use of the finite-state serial processing abilities shared with many other species. I propose that human general hierarchical abilities are supported anatomically by the great enlargement of Broca's area in our species, along with the broadening of its connections to large portions of the parietal and temporal lobes. Computationally, Broca's region in humans may act as a domain-general "stack", or auxiliary memory, supporting supra-regular computation in both language and music.