The Influence of Olfactory Context on the Perception of Emotional Facial Expressions: The Moderating Role of Anhedonia

The present study investigated whether olfactory context influences the processing of ambiguous happy and fearful facial expressions at both the behavioral and neural level, and whether this influence depends on individual differences in anhedonia, indexed continuously by SHAPS scores. Hypothesis 1 predicted that higher SHAPS scores would be associated with reduced neural responsiveness specifically to happy facial expressions, with no comparable reduction expected for fearful faces. Hypothesis 2 predicted that anhedonia would moderate the facilitatory effect of pleasant olfactory context on happy facial expressions, such that it would be attenuated at higher levels of anhedonia. At the behavioral level, independently of anhedonia and olfactory context, facial expression exerted a consistent effect on how the ambiguous stimuli were processed. Fearful expressions were categorized less accurately than happy expressions, and both the categorization response and the subsequent intensity judgment were slower for fearful than for happy expressions. Both expressions were morphed to the same, relatively low intensity (20%), meaning that the distance from the neutral baseline was equal across emotions. The fact that fearful expressions were harder to categorize points to a difference in perceptual similarity, consistent with previous descriptions of the greater perceptual similarity between fearful and neutral facial configurations relative to happy and neutral configurations (Wieser et al., 2014). This baseline asymmetry provides the context against which the role of anhedonia should be interpreted. Anhedonia is characterized by a diminished capacity to experience pleasure and reduced responsiveness to rewarding stimuli. Beyond reward dysfunction, it has been associated with altered emotional processing, reduced sensitivity to positive information, and atypical interpretation of social cues. Because pleasant odors can act as rewarding affective signals, individuals with elevated anhedonia may be less responsive to their modulatory effects during emotion perception. The present study aims to investigate whether olfactory context influences the perception of ambiguous emotional facial expressions and whether this relationship is moderated by individual differences in anhedonia. A non-clinical sample of adults will complete an emotional categorization task using low-intensity morphed happy and fearful faces presented under three olfactory conditions: a pleasant odor (lavender), an unpleasant odor (isovaleric acid), and an odorless control condition. Behavioral measures will include emotion categorization, perceived emotional intensity, and reaction time. Individual levels of anhedonia will be assessed using a standardized self-report questionnaire. Simultaneously, electroencephalographic activity will be recorded to examine event-related potentials associated with multisensory emotional processing. It is expected that olfactory context will bias the interpretation of ambiguous facial expressions in a valence-congruent manner, while higher levels of anhedonia will attenuate the influence of pleasant olfactory cues because of reduced sensitivity to rewarding information. By integrating behavioral and electrophysiological measures, this study seeks to advance the understanding of how reward-related individual differences influence multisensory emotion perception and the neural mechanisms underlying social-emotional processing.

The interpretation of emotional facial expressions is a fundamental component of social cognition. However, emotional faces, particularly those with low emotional intensity or uncertain valence, are rarely processed in isolation and are often influenced by contextual information from other sensory modalities. Olfactory cues represent a particularly relevant source of affective context due to the close anatomical and functional connections between the olfactory system and neural networks involved in emotion, memory, and reward processing. Although previous research has demonstrated that odors can influence the perception of emotional faces, little is known about how individual differences in anhedonia shape this multisensory process. Anhedonia is characterized by a diminished capacity to experience pleasure and reduced responsiveness to rewarding stimuli. Beyond reward dysfunction, it has been associated with altered emotional processing, reduced sensitivity to positive information, and atypical interpretation of social cues. Because pleasant odors can act as rewarding affective signals, individuals with elevated anhedonia may be less responsive to their modulatory effects during emotion perception. The present study aims to investigate whether olfactory context influences the perception of ambiguous emotional facial expressions and whether this relationship is moderated by individual differences in anhedonia. A non-clinical sample of adults will complete an emotional categorization task using low-intensity morphed happy and fearful faces presented under three olfactory conditions: a pleasant odor (lavender), an unpleasant odor (isovaleric acid), and an odorless control condition. Behavioral measures will include emotion categorization, perceived emotional intensity, and reaction time. Individual levels of anhedonia will be assessed using a standardized self-report questionnaire. Simultaneously, electroencephalographic activity will be recorded to examine event-related potentials associated with multisensory emotional processing. The present study investigated whether olfactory context influences the processing of ambiguous happy and fearful facial expressions at both the behavioral and neural level, and whether this influence depends on individual differences in anhedonia, indexed continuously by SHAPS scores. Hypothesis 1 predicted that higher SHAPS scores would be associated with reduced neural responsiveness specifically to happy facial expressions, with no comparable reduction expected for fearful faces. Hypothesis 2 predicted that anhedonia would moderate the facilitatory effect of pleasant olfactory context on happy facial expressions, such that it would be attenuated at higher levels of anhedonia. At the behavioral level, independently of anhedonia and olfactory context, facial expression exerted a consistent effect on how the ambiguous stimuli were processed. Fearful expressions were categorized less accurately than happy expressions, and both the categorization response and the subsequent intensity judgment were slower for fearful than for happy expressions. Both expressions were morphed to the same, relatively low intensity (20%), meaning that the distance from the neutral baseline was equal across emotions. The fact that fearful expressions were harder to categorize points to a difference in perceptual similarity, consistent with previous descriptions of the greater perceptual similarity between fearful and neutral facial configurations relative to happy and neutral configurations (Wieser et al., 2014). This baseline asymmetry provides the context against which the role of anhedonia should be interpreted.