phi-phenomenon

phi-phenomenon

(ˈfaɪfɪˌnɒmɪnən)
n, pl -na (-nə)
1. (Psychology) the illusion that when two lights are rapidly turned on and off in succession something appears to move backwards and forwards between them while the lights stay stationary
2. (Psychology) a similar illusion in which one light appears to move smoothly backwards and forwards
[C20: arbitrary use of Greek phi]