Unconscious odour conditioning in human subjects.

In the first session, two groups of male and female subjects were given a stressful task involving the completion of eleven WAIS block patterns under time limitations. A low intensity of a neutral odour (TUA) was present for half of the subjects. During a second session several days later, subjects completed a mood rating scale and then entered a room, where the odour of TUA was present, to judge a series of photographs of people and complete a second mood rating scale. During the first session female subjects completed significantly fewer block patterns, and completed fewer correct designs. In the second session, female subjects who had experienced TUA odour in the stress condition showed an increase in anxiety ratings. They also had higher ratings scores when judging the photographs. In contrast, subjects who did not experience odour during the stress session became calmer during the second session. None of the female subjects reported perceiving the odour irn either session. As both pairing and elicitation occurred at low levels of awareness, the study demonstrates how odours might acquire values through pairing with emotionally significant events.