Non-associative

Meaning: Non-associative learning is a lasting change in response to a stimulus after repeated exposure, with no pairing to a second stimulus (classical conditioning) and no link to a reinforcement or punishment (operant conditioning). Habituation is a decreased response to a repeated, harmless stimulus, like tuning out a ticking clock. Sensitization is an increased response, often after an intense or threatening stimulus, and it can spread to other stimuli. Dishabituation is the return of a habituated response after a new or strong stimulus.

On the MCAT: A passage describes repeated trials with one stimulus, often with a graph of response size over time. A falling response points to habituation; a rising response points to sensitization. To classify the learning, check for pairing or reinforcement. If neither is present, it is non-associative. Gill withdrawal in the sea slug Aplysia is a standard example.

Common confusion: Habituation is not the same as sensory adaptation or fatigue. Sensory adaptation occurs at the receptor level, whereas habituation is a learned change in the behavioral or neural response. If a novel stimulus restores the response (dishabituation), simple fatigue is not the explanation.