 In a seminal contribution, Turing (1936) introduced what is now called the    Turing machine: an abstract model  of an idealized computing device. A Turing machine contains a central processor, governed by precise mechanical rules, that manipulates symbols inscribed along a linear array of memory locations. Impressed by the enormous power of the Turing machine formalism, many researchers seek to construct computational models of core mental processes, including reasoning, decision-making, and problem solving. This enterprise bifurcates into two main branches. The first branch is artificial intelligence (AI), which aims to build “thinking machines”. Here the goal is primarily an engineering one—to build a system that instantiates or at least simulates thought—without any pretense at capturing how the human mind works. The second branch, computational psychology, aims to construct computational models of human mental activity. AI and computational psychology both emerged in the 1960s as crucial elements in the new interdisciplinary initiative   cognitive science, which studies the mind by drawing upon psychology, computer science (especially AI), linguistics, philosophy, economics (especially game theory and behavioral economics), anthropology, and neuroscience.