Odors Are More Sensitive to Evaluative Conditioning than Sounds

Stimuli of different modalities can acquire an affective value via evaluative conditioning. This process describes a shift in perceived affective quality of a neutral stimulus towards the hedonics of an associated affective stimulus. The olfactory system, as compared to other modalities, might be especially prone to attributing affective value to an odor due to its close neuroanatomical connectivity with brain regions processing emotion.

In the present study, we investigated whether perceived affective quality of odors is more sensitive to evaluative conditioning than that of sounds. For this purpose, 48 healthy participants (50% male) rated unfamiliar and emotionally neutral odors and sounds before and after pairing with either aversive or neutral pictures.

Our results show a stronger decrease in odor valence and stronger increases in arousal and dominance ratings for odors paired with aversive compared to neutral pictures. For sounds, ratings of valence, arousal, and dominance were independent of picture emotionality.

Odors appear to be more sensitive to evaluative conditioning than sounds. Our findings extend existing modality comparisons mainly focusing on characteristics of odor-associated memories by specifically looking at affective quality of the odor itself in associative learning.

Perceived affective quality of a stimulus goes along with the tendency to approach or avoid this stimulus. For odors, it is especially prone to change into an aversive direction. This may have implications for food and fragrance choices but also for the understanding of clinical conditions in which odors become highly aversive, such as post-traumatic stress disorder.