The "jump" and "release" effects: some observations on the perception of causality.

Two experiments studied the "release" and "jump" effects. Suppose that--on a homogeneous background--a single object moving on a straight trajectory has a constant physical velocity along all its path except in the middle where this velocity is higher or lower for a short time. The release effect occurs when this velocity is lower and the jump effect when it is higher. In the release effect, the object appears to be released from something that held it back. In the jump effect, the object appears to make a jump forward. In line with Premack's 1990 view, these effects suggest a reclassification of causal phenomena in terms of the perceived origin of the change in movement. This origin is perceived as external in Michotte's launching effect and as both internal and external in the release effect and as internal in the jump effect.