Attentional Modulation of Contamination Sensitivity in Complex Odour Mixtures: Sharper Perceptual Boundaries for Food compared to Non-Food Odours

Processing of contaminants in odour mixtures is influenced by their categorisation into food and non-food categories. For example, we previously found that participants were more likely to perceive food odours as contaminated by non-food odours than vice versa, and that this effect was robust to changes in explicit task instructions. However, due to the mixing of food and non-food components, processing differences between categories were not captured by this task design and thus remain to be explored. In the current pre-registered study, we address this knowledge gap by determining the effects of attention on the perception of odour mixtures containing only food or non-food components. Participants (N = 24) assessed the perceived dominance of a target odour within an odour mixture. Response times to all odours increased towards the dilution series’ midpoint and were faster for food odour compared to non-food odour mixtures. Perceived target dominance increased linearly for non-food targets but exhibited a sigmoidal shape with a steeper slope (smaller just-noticeable difference) for food targets. This implies that distinguishing two food odours was easier than distinguishing between two non-food odours, likely due to definitions higher relevance of distinct object category boundaries subserving contamination avoidance. At the same time, contamination sensitivity might be lower for non-foods, allowing for greater tolerance of deviations. Attention did not influence the perception of non-food but did so for ambivalent food mixtures and when the target was completely absent.