Special Issue on The Brain Mechanisms of Imitation Learning

For a long time, imitation learning has been a key topic of psychology and cognitive sciences. Recent progress in neurosciences has, however, opened the way to a better understanding of the neural foundations of the complex mechanisms of imitation and has formed the basis for computational studies of its neural correlates. A key event in this development was the discovery of the so-called ‘mirror neuron system’. While evidence that specialized areas of the human brain contribute to imitation had long been suspected from results of various lesion studies (Nichelli, DeRenzi, & Motti, 1980; Serdaru, Lhermite, & Pillon, 1986; Shimomura & Mori, 1998), the mirror neuron system was found in normally behaving subjects. The mirror neuron system refers to a network of brain areas in premotor and parietal cortices that is activated by both the recognition and the production of the same kind of object oriented movements performed by oneself and by others—see Decety, Chaminade, Grezes, and Meltzoff (2002) Iacoboni et al. (2001) Rizzolatti, Fogassi, and Gallese (2001) for recent reports on this system in monkeys and humans, and its link to imitation. Inspired by the mirror neuron system, imitation learning has also become again a core topic of research in robotics (Billard, 2001; Dautenhahn, 1995; Matarić, 2002; Schaal, 1999), after the original wave of robotic imitation based on symbolic artificial intelligence methods lost its thrust in the late 1980s. Endowing robots and other machines with the ability to learn from observing and interacting with humans would have numerous advantages as tool to accomplish flexible means of human–robot interaction. First and foremost, imitation learning is a powerful mechanism for reducing the complexity of search spaces for learning. When observing either good or bad examples, one can