Can ambient odors influence the recognition of emotional words? A behavioral and event-related potentials study

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.

The processing characteristics of bodily expressions under the odor context: An ERP study

The recognition of facial expressions has been shown to be influenced by contextual odors. The aims of this study were (1) to investigate whether odor has a similar effect on the recognition of bodily expressions, and (2) to analyze the time-course of such effects. Sixty-nine adults were randomized into three groups to identify bodily expressions (happy, fearful, and neutral) in three odor environments (pleasant odor, unpleasant odor, and no odor). Event-related potentials (ERPs) induced by the viewing bodily expressions were analyzed. Behaviorally, the unpleasant odor context promoted the recognition of bodily expressions. The ERP results showed odor influences on bodily expression recognition in two phases. In a middle stage phase (150-200 ms post-stimulus onset), VPP amplitudes induced by bodily expressions were greater in an unpleasant odor context than in a pleasant odor context. In a mid-late stage phase (beyond 200 ms), an interaction between contextual odor and bodily expression type was observed. When exposed to an unpleasant contextual odor, N2 and LPP amplitudes related to fearful bodily expressions were smaller than when exposed to other odor contexts, showing the promoting effect of mood coherence effect. Behavioral and ERP evidence confirmed that contextual odor can modulate the visual processing of bodily expressions, with an overall promoting effect of an unpleasant odor on bodily expression processing (phase one) and a specific modulating influence of odors on affectively congruent/incongruent bodily expressions (phase two).

The scent of attraction and the smell of success: crossmodal influences on person perception

In recent decades, there has been an explosion of research into the crossmodal influence of olfactory cues on multisensory person perception. Numerous peer-reviewed studies have documented that a variety of olfactory stimuli, from ambient malodours through to fine fragrances, and even a range of chemosensory body odours can influence everything from a perceiver's judgments of another person's attractiveness, age, affect, health/disease status, and even elements of their personality. The crossmodal and multisensory contributions to such effects are reviewed and the limitations/peculiarities of the research that have been published to date are highlighted. At the same time, however, it is important to note that the presence of scent (and/or the absence of malodour) can also influence people's (i.e., a perceiver's) self-confidence which may, in turn, affect how attractive they appear to others. Several potential cognitive mechanisms have been put forward to try and explain such crossmodal/multisensory influences, and some of the neural substrates underpinning these effects have now been characterized. At the end of this narrative review, a number of the potential (and actual) applications for, and implications of, such crossmodal/multisensory phenomena involving olfaction are outlined briefly.

Prior exposure to Hedione, a model of pheromone, does not affect female ratings of male facial attractiveness or likeability

The existence of pheromones in humans is controversial, partly because of definitional difficulties and partly because of the question of possible chemical substances. The synthetic compound Methyl dihydrojasmonate (Hedione) is potent to bind to vomeronasal-type 1 receptors (VN1R1s) and activate limbic areas of the brain in a sex-specific manner. However, one of the most important definitional points for a human pheromone effect has not yet been investigated, i.e., whether smelling Hedione, a model of pheromone, has a behavioral effect. We tested in females whether Hedione leads to altered perception of male social stimuli. Each of the included women were sensitive to Hedione and were tested around the time of ovulation in three consecutive sessions, during each they were exposed to either Hedione or Phenylethyl alcohol or Odorless air. We measured the speed of male face recognition (implicit priming task) and collected ratings of facial attractiveness and likeability of men (explicit task). Only about half of the women tested were sensitive to Hedione. Those women did not show any effect of Hedione exposure in the implicit priming task and moderate, but non-significant effects in the explicit task. We therefore assume that Hedione is not a potent model of pheromone in humans and this observation may be due to the fact that the artificially produced substance is not suited for signaling the proximity of other humans. Furthermore, the high rate of Hedione-specific anosmia leads to the hypothesis that a substantial proportion of individuals has a poor V1NR1 receptor expression.

A Review of the Effects of Valenced Odors on Face Perception and Evaluation

How do valenced odors affect the perception and evaluation of facial expressions? We reviewed 25 studies published from 1989 to 2020 on cross-modal behavioral effects of odors on the perception of faces. The results indicate that odors may influence facial evaluations and classifications in several ways. Faces are rated as more arousing during simultaneous odor exposure, and the rated valence of faces is affected in the direction of the odor valence. For facial classification tasks, in general, valenced odors, whether pleasant or unpleasant, decrease facial emotion classification speed. The evidence for valence congruency effects was inconsistent. Some studies found that exposure to a valenced odor facilitates the processing of a similarly valenced facial expression. The results for facial evaluation were mirrored in classical conditioning studies, as faces conditioned with valenced odors were rated in the direction of the odor valence. However, the evidence of odor effects was inconsistent when the task was to classify faces. Furthermore, using a z-curve analysis, we found clear evidence for publication bias. Our recommendations for future research include greater consideration of individual differences in sensation and cognition, individual differences (e.g., differences in odor sensitivity related to age, gender, or culture), establishing standardized experimental assessments and stimuli, larger study samples, and embracing open research practices.

α-Pinene odor exposure enhances heat stress tolerance through Daf-16 in Caenorhabditis elegans

Aromatherapy has been widely used as complementary and alternative medicine to reduce pain and induce sleep. However, the scientific evidence regarding the biological effects of odor is scarce and the underlying molecular mechanisms have not been clarified. We treated worms with contactless S-(-)- and R-(+)-α-pinene and analyzed heat stress tolerance. Odor stimulation induced motility recovery after incubation at 35 °C for 4 h. This increase in heat stress tolerance was not present in odr-3 mutants and daf-16 mutants. S-(-)- and R-(+)-α-pinene expanded health span and increased fat accumulation. Moreover, S-(-)- and R-(+)-α-pinene modulated the expression of 84 and 54 genes, respectively. These results show that α-pinene odor stimulation is related to stress tolerance, lipid metabolism, and health span via some specific signaling pathways. This study may provide a potential target for antiaging and disease prevention.

Unpleasant Food Odors Modulate the Processing of Facial Expressions: An Event-Related Potential Study

In real-life situations, emotional information is often expressed through multiple sensory channels, with cross-talk between channels. Previous research has established that odor environments regulate the recognition of facial expressions. Therefore, this study combined event-related potentials (ERPs) with a facial emotion recognition task to investigate the effect of food odor context on the recognition of facial expressions and its time course. Fifty-four participants were asked to identify happy, fearful, and neutral faces in an odor context (pleasant, unpleasant or neutral). Electroencephalography (EEG) was performed to extract event-related potentials (ERPs). Behaviorally, unpleasant food odors triggered faster recognition of facial expressions, especially fearful ones. ERP results found that in the early stage, unpleasant food odors within 80–110 ms evoked a larger P100 amplitude than pleasant food odors and no odors, which showed that the unpleasant odor environment promoted the rapid processing of facial expressions. Next, the interaction between odor environment and facial expressions occurred during the middle stage, and the fearful expression evoked a smaller VPP (vertex positive potential) amplitude than the happy and neutral expressions when exposed to the unpleasant food odor environment. This result indicates that unpleasant odor environment consumed fewer cognitive resources when judging fearful expression, showing the promoting effect of mood coherence effect. These findings provided evidence for how people chose odor environments to facilitate the recognition of facial expressions, and highlighted the advantages of unpleasant food odors in communicating emotional information across the olfactory and visual pathways.

Background odors affect behavior in a dot-probe task with emotionally expressive faces

Odors affect perception of social cues in visual environments. Although often underestimated, people use their sense of smell to guide approach or avoidance behavior in social contexts. However, underlying psychological mechanisms are not well known. Prior work suggested olfactory effects are due to increased attention or arousal, or depend on the congruency between olfactory and visual cues. Our aim was to assess how odors influence attentional processes using a dot-probe task with odor-congruent and odor-incongruent facial expressions (happy, disgusted and neutral expressions paired with pleasant odor, unpleasant odor and no-odor). In a preregistered analysis plan, we hypothesized either faster reaction times attributed to arousal from odors in general, or to faces that were emotionally congruent with the odors. We also hypothesized time-on-task effects specific to the odor compared to the control condition. Using Bayesian linear models, we found strong evidence that the faces were rated as more arousing and emotional in odor contexts. However, the dot-probe task did in fact not provide an effective cue to selective visual attention, and odors did not modulate overall attention to the faces. However, we found a time-on-task effect such that in the unpleasant odor condition, response times decreased over time, whereas in the no-odor and pleasant condition there was a slight increase in response times. We conclude that time-on-task effects is an interesting venue for odor-visual interaction research, and such effects might explain inconsistent findings in the prior research literature.