What psychological phenomenon does the phrase "The fisherman does not hook a fish with every cast of the line" best describe?

A) stimulus generalization
B) shaping
C) primary reinforcement
D) partial reinforcement

This phrase best describes the phenomenon of partial reinforcement, where a behavior is not reinforced every time it occurs, leading to a slower rate of learning but a more persistent behavior once learned. Just like a fisherman doesn't catch a fish with every cast, a behavior may not always be rewarded, but the subject keeps performing it in the hopes of being reinforced eventually.