Kubovy Perception Lab
UVA Lab


Velocity, Distance, and Time

Since we now knew that only the motion after the impact was important and that the horizontal motion did not matter, we were left to analyze the movement in a line from point A (impact) to point B (stopping point). This motion could be completely described by velocity, distance, time, acceleration, and jerk (the derivative of acceleration).

First we designed an experiment to examine the velocity, distance, and time variables, ignoring acceleration and jerk. To determine which of these variables change the perceived duration rating we created three conditions. In one condition the amount of time the dot moved after impact was held constant while the speed it rebounded (and thus the distance it travelled) was changed. In another condition the distance travelled after rebound was held constant, but the dot moved faster or slower to cover that distance in a shorter or longer time. In the third condition the velocity of the dot was held constant after impact, but it was allowed to cover either a longer distance over a longer time or a shorter distance over a shorter time.

If, for instance, time was the only important variable then we should observe the effect only when time is varied. Thus, in the condition in which the "time" variable was held constant the long and short versions of the video should affect perceived duration in the same way. We hypothesized that time travelled after impact would be the important variable, with distance and velocity of the motion path being unimportant. The results confirmed this hypothesis.

 

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