Abstract
Odor context can affect the recognition of facial expressions. However, there is no evidence to date that odor can regulate the processing of emotional words conveyed by visual words. An emotional word recognition task was combined with event-related potential technology. Briefly, 49 adults were randomly divided into three odor contexts (pleasant odor, unpleasant odor, and no odor) to judge the valence of emotional words (positive, negative, and neutral). Both behavioral and Electroencephalography (EEG) data were collected. Both the pleasant odor and unpleasant odor contexts shortened the response time of the subjects to emotional words. In addition, negative words induced greater amplitudes of early posterior negativity (EPN) and late positive potential (LPP) than the positive and neutral words. However, the neutral words induced a larger N400 amplitude than the positive and negative words. More importantly, the processing of emotional words was found to be modulated by external odor contexts. For example, during the earlier (P2) processing stages, pleasant and unpleasant odor contexts induced greater P2 amplitudes than the no odor context. In the unpleasant odor context, negative words with the same odor valence induced greater P2 amplitudes than the positive words. During the later (N400) stages, various regions of the brain regions exhibited different results. For example, in the left and right frontal areas of the brain, exposure to positive words in a pleasant odor context resulted in a smaller N400 amplitude than exposure to neutral words in the same context. Meanwhile, in the left and right central regions, emotional words with the same valence as pleasant or unpleasant odor contexts elicited the minimum N400 amplitude. Individuals are very sensitive to emotional information. With deeper processing, different cognitive processes are reflected and they can be modulated by external odors. In the early and late stages of word processing, both pleasant and unpleasant odor contexts exhibited an undifferentiated dominance effect and could specifically modulate affectively congruent words.
Highlights
People feel relaxed and happy when they smell the fragrance of flowers, and they feel disgusted when they smell moldy food
The pleasantness score was highest for the pleasant environment, followed by the no odor environment (p \ 0.001) and the unpleasant odor environment (p \ 0.001)
It was observed that the speed of emotional word recognition was affected by the external odor environment
Summary
People feel relaxed and happy when they smell the fragrance of flowers, and they feel disgusted when they smell moldy food. Many studies had shown that when people smelt different odors, the valence scores or recognition speed of facial or bodily expression showed different performance. In a study conducted by Cook et al (2017), odors were found to enhance assessed valence in an interactive manner (e.g., disgusting faces are perceived as more negative in an unpleasant odor environment) (Cook et al 2017). Cook et al (2015) demonstrated that odor valence affects evaluations of the valence of neutral faces (Cook et al 2015). Food odors can affect the recognition of facial expressions. Unpleasant food odors prompt people to recognize facial expressions more quickly, especially fearful expressions (Li et al 2020). Li and Wang found that unpleasant odor context promoted the recognition of bodily expressions (Li and Wang 2021). Preliminary neurological evidence further suggests that emotional odors modulate responses of the visual cortex to emotional faces (Forscher and Li 2012; Seubert et al 2010)
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