The evolution of learning.

Most processes or forms of learning have been treated almost as special creations, each as an independent process unrelated to others. This review offers an evolutionary cladogram linking nearly one hundred forms of learning and showing the paths through which they evolved. Many processes have multiple forms. There are at least five imprinting processes, eleven varieties of Pavlovian conditioning, ten of instrumental conditioning, and eight forms of mimicry and imitation. Song learning evolved independently in at least six groups of animals, and movement imitation in three (great apes, cetaceans and psittacine birds). The cladogram also involves at least eight new processes: abstract concept formation, percussive mimicry, cross-modal imitation, apo-conditioning, hybrid conditioning, proto-pantomime, prosodic mimicry, and image-mediated learning. At least eight of the processes evolved from more than one source. Multiple sources are of course consistent with modern evolutionary theory, as seen in some obligate symbionts, and gene-swapping organisms. Song learning is believed to have evolved from two processes: auditory imprinting and skill learning. Many single words evolved from three sources: vocal mimicry, discrimination learning, and abstract concept formation.