a man was trapped behind a refrigerator and nearly suffocated. subsequently, he has a phobia of tight, enclosed spaces and is afraid to ride on small, crowded elevators. however, he has no fear of large, uncrowded elevator rides. the man's fear of small elevators is an example of and his lack of fear toward large elevators is an example of

The man's fear of small elevators is an example of "stimulus generalization", and his lack of fear toward large elevators is an example of "stimulus discrimination".

Stimulus generalization refers to the propensity for stimuli like a unique stimuli in a learning worldview to deliver a reaction approximating that learnt under the first condition. A generalization inclination can be drawn up demonstrating that the more comparable the stimuli the more comparable the reactions.
Stimulus discrimination refers to a phenomenon recognized in behaviorist learning theory, the individual figures out how to recognize, for reaction purposes, between comparable stimuli.