Mr. Schab, who did the experiments while at Yale University, now does psychological research at the General Motors Research Laboratories in Warren, Mich. He presented his results in this month's issue of The Journal of Experimental Psychology: Learning, Memory and Cognition.

''People seem to believe from their own experiences that odors are special, in the sense that they can recall very vividly events from 20, 30 years ago,'' he said.

Aroma and Emotion

Mr. Lyman said odors, unlike sights or sounds, are processed through the brain's limbic system, which is involved in emotions. That might help odors bring back memories with emotional overtones, he said.

In one experiment, 72 Yale undergraduates were presented with a list of 40 common adjectives and told to write down the opposite of each word. They were not told that the next day they would be asked to recall the words they had written.

Each student was exposed to a chocolate smell during the word exercise only, during the later recall test only, on both occasions or on neither. All students were told to imagine the smell of chocolate on both occasions.