Perceived kinetics in launching and triggering events

In launching and triggering effects [Michotte, 1946 La Perception de la Causalite¨ (Louvain: Publi- cations Universitaires)] object A moves towards object B and, when the two objects make contact, B starts to move. Phenomenally, the movement of A appears to cause the movement of B: either mechanically, in launching, or psychologically, in triggering. Perceived kinetics of these events have been explored in four experiments. We measured P50, the point of subjective equality between experimental stimulus and standard stimulus, of the perceived velocity of B. We found that P50 in control condition, obtained on adding a pause before the motion of B (P50 = -0.005 deg s-1 ), is different from P50 of experimental conditions: in launching (i) the P50 is 0.56 deg s-1; in triggering (ii) the P50 is 0.42 deg s-1. Moreover, in launching para- digm, P50 is also affected by kinetic variations of the objects before and after the collision, related to the impression of `force' of the impact. In the decreased-force condition (iii) a small effect is found: P50 is 0.34 deg s-1; in the increased-force condition (iv) the P50 is 0.96 deg s-1. These results suggest that kinetic properties of causal and triggering displays are based on the global organisation of the events.