APA Dictionary of Psychology

the process by which consciousness arose and developed as a biological adaptation in animals. In mammals, conscious wakefulness, attentional orienting, sensory perception, immediate memory, and so forth are associated with the evolution of the thalamocortical system of the mammalian brain over more than 200 million years. Close functional parallels may exist in birds, some cephalopods, and reptiles such as salamanders and crocodilia.