AP Psychology Practice Test

Which phenomenon is an example of an illusion?

1. Shape constancy

2. Perceptual set

3. Phi phenomenon

4. Perceptual adaptation

The correct answer is: Phi phenomenon

The phi phenomenon is indeed an example of an illusion. It refers to the optical illusion of perceiving continuous motion between separate objects viewed in rapid succession. This is commonly experienced in film and animation, where a series of still images presented in quick succession create the illusion of movement. The brain interprets these individual frames as a fluid motion, highlighting the way our perception can be influenced by the timing of visual stimuli. Shape constancy and perceptual adaptation relate to how we perceive objects under varying conditions, but they are based on the brain's ability to maintain a stable perception despite changes in sensory input. Perceptual set involves a tendency to perceive things in a certain way based on expectations, past experiences, or context. While these concepts are relevant to perception, they do not specifically demonstrate an illusion like the phi phenomenon does.