The Perception Of Falling Objects

Aristotle believed that objects fell at a constant velocity, which raised the possibility that people's visual perception of falling motion might be biased away from acceleration towards constant velocity. I tested this idea by requiring participants to judge whether a ball moving in a simulated naturalistic setting appeared to accelerate or decelerate, as a function of its motion direction and the amount of acceleration/deceleration. I found that the point of subjective constant velocity (PSCV) differed between up and down but not between left and right motion directions, which indicated that more acceleration was needed for a downward-falling object to appear at constant velocity than for an upward “falling” object. I found no significant differences in sensitivity to acceleration for the different motion directions. My results support the idea that Aristotle's belief may in part be due to a bias that reduces the perceived magnitude of acceleration for falling objects.