Book excerpt: Originally published in 1963, this is a classic work on the psychology of perception. By means of suitable patterns on a partly concealed rotating disc Michotte was able to give the impression of objects in movement; and where certain conditions of speed, position, and time-interval were satisfied, his subjects received the impression of a causal interaction between two objects – for example, the impression that one object has ‘bumped into’ another (the ‘Launching Effect’) or is carrying it along (the ‘Entraining Effect’). In a further group of experiments Michotte studies the conditions in which moving objects look as though they are alive. A large number of experiments are described, and on the basis of them Michotte formulates a theory as to the conditions in which causal impressions occur. He also compares his own views on causality with those of Hume, Maine de Biran, and Piaget.