Final answer:
Jay's fear is an example of stimulus generalization, where a response to a specific stimulus is spread to similar situations, leading to the same fearful response in any confined space.
Step-by-step explanation:
Jay's fear of confined spaces resulting from the intense fear he experienced on the subway can be explained by stimulus generalization. This psychological phenomenon occurs when a response to a specific stimulus becomes associated with similar stimuli, leading to the same response despite differences in the original and new stimuli. In Jay's case, the confined space of the subway, alongside the sudden halt and the loss of balance, has become a conditioned stimulus for the intense fear response. Now, any environment that feels confined triggers Jay's physiological and emotional arousal, indicating a generalization from the original fear-inducing situation to similar environments.