Olfactory habituation is a reduced behavioural response to repetitive odour stimulation which can be modulated by both bottom-up and top-down processes. Edibility is a top-down feature that can affect olfactory perception, but whether and how it can modulate olfactory habituation remains unclear. Further, food stimuli attract attention due to their intrinsic salience, which might slow down habituation. Here, we investigated whether olfactory habituation shows a different trend to food or non-food odours. Fifty participants were tested under fasted and fed states in separated sessions. In each session, participants were exposed to the same food and non-food odour in blocks of 20 trials. They rated the perceived odour intensity and pleasantness after each trial. Linear mixed-effects models showed that, regardless of the participants' hunger state, the perceived odour intensity decreased over time only for non-food odours (p=0.007). Conversely, the odour pleasantness decreased more significantly across trials for food (vs. non-food) odours (p<0.001). Our results showed that odour edibility modulates olfactory habituation, supporting the olfactory specific satiety theory, which describes a decrease in the pleasantness of an odour of food repeatedly smelled, without changes in the perceived intensity. However, the influence of other bottom-up features (e.g., trigeminality) cannot be ruled out. To minimize such influences, we are conducting an experiment in which participants complete the same habituation paradigm while being presented with a perceptually malleable odour in terms of edibility. The perceived odour edibility of vanilla odour is induced following a conditioning protocol and participants are assigned to one of two groups (edible vs. non-edible). We hypothesize a habituation trend in the edible (vs. non-edible) group like the one obtained in the above research for food (vs. non-food) odours, respectively.

This work was funded by the University of Trento.