Olfactory Stimulation Modulates Visual Perception Without Training

Considerable research shows that olfactory stimulations affect other modalities in high-level cognitive functions such as emotion. However, little known fact is that olfaction modulates low-level perception of other sensory modalities. Although some studies showed that olfaction had influenced on the other low-level perception, all of them required specific experiences like perceptual training. To test the possibility that olfaction modulates low-level perception without training, we conducted a series of psychophysical and neuroimaging experiments. From the results of a visual task in which participants reported the speed of moving dots, we found that participants perceived the slower motions with a lemon smell and the faster motions with a vanilla smell, without any specific training. In functional magnetic resonance imaging (fMRI) studies, brain activities in the visual cortices [V1 and human middle temporal area (hMT)] changed based on the type of olfactory stimulation. Our findings provide us with the first direct evidence that olfaction modulates low-level visual perception without training, thereby indicating that olfactory-visual effect is not an acquired behavior but an innate behavior. The present results show us with a new crossmodal effect between olfaction and vision, and bring a unique opportunity to reconsider some fundamental roles of olfactory function.

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.

On Knowing What You Like and Liking What You Smell: Attitudes Depend on the Form in Which the Object is Represented

Attitudes are learned predispositions to respond in a consistently favorable or unfavorable manner with respect to a given object. Three studies examined whether responses elicited by an attitude object depend on the form in which the object is mentally represented. Subjects indicated their preferences for odors in response to descriptive labels (a symbolic representation) and in response to unlabeled scratch-and-sniff patches (a perceptual representation). The correspondence between ratings of symbolic and perceptual object representations was substantially lower than the reliability of ratings within either representational domain. Accessibility of attitudes (indexed by judgment times) was increased by prior expression of attitudes within the same representational domain but not by prior expression of attitudes in the other domain. Discussion considers the importance of these results for models of attitude structure and function.

Olfaction and Human Social Behavior

A total of 94 undergraduate males participated in an experiment designed to examine the impact of a pleasant scent (perfume) on interpersonal attraction and social perception. Subjects met and interacted briefly with one of two female confederates who either wore perfume or did not, and who were dressed either neatly (in a blouse, skirt, and hose) or informally (in jeans and a sweatshirt). Results indicated that the presence of a pleasant scent increased attraction toward the confederates and produced positive shifts in perceptions of several of their traits when they were dressed informally. When the confederates dressed in a neater manner, however, opposite effects were observed. These findings were interpreted as stemming from the fact that subjects reacted more favorably to the confederates when they appeared to be intermediate rather than high or low along a dimension of informality-formality.

Sex differences in task performance associated with attention to ambient odor

The effects of ambient odor (pleasant, unpleasant, none); odor suggestion (present, absent); and sex of subject on mood and performance measures were explored in a 3 x 2 x 2 experimental design. A total of 40 men and 40 women performed a clerical task and a speed and accuracy task (digit deletion), filled out self-evaluations of mood, predicted performance, and rated the odor quality of the test room. Ambient odor conditions significantly affected room smell ratings, but they had no effect on performance or mood. Odor suggestion produced a significant sex-related interaction effect on the digit deletion task, irrespective of actual ambient odor. The results are discussed with respect to sex differences observed in laboratory studies and in epidemiological investigations of multiple chemical sensitivity and sick building syndrome.

Olfactory remediation: current evidence and possible applications

A number of recent psychological investigations has suggested a significant role for olfactory stimulation in the alteration of cognition, mood and social behaviour. These orthodox investigations have a common, if uneasy, relationship with the holistic practice of so-called aromatherapy. This paper reviews the therapeutic effects of dour on health-related behaviour. It distinguishes two types of research activity, one which is quantitative and science- and medicine-based, the other which is qualitative and anecdote- and experience-based. Both of these endeavours are critically assessed and suggestions are made for improvement in methodology and experimental design.

Emotional qualities of odors and their influence on the startle reflex in humans

Recent human and animal research suggests that the startle reflex might serve as a psychophysiological indicator of the emotional valence of foreground stimulation. The present experiment was designed to evaluate the emotional effects of positive and negative odorant stimuli. We examined the effects of continuous hydrogen sulphide (H2S) and vanillin stimulation on the magnitude of the acoustic startle reflex (measured at the M. orbicularis oculi) and on ratings of subjective valence in 16 healthy subjects. In accordance with the view that odors have emotional qualities, we found that H2S, a presumed negative foreground stimulus, significantly enhanced the startle-reflex amplitude relative to neutral air stimulation, whereas vanillin, a positive foreground stimulus, tended to reduce the reflex amplitude compared with neutral air stimulation. Both odorant stimuli were rated as equally intense by the subjects, and heart rate and electrodermal activity were not affected differentially by the two odorants.

EFFECT OF COMPOSITION OF OLFACTORY CUES ON IMPRESSIONS OF PERSONALITY

Ninety female undergraduates participated in an experiment investigating whether composition of three fragrances (perfumes) influenced impressions of personality traits of people who would wear each fragrance. Analysis of covariance with the variance due to liking of the fragrance (a covariate) removed, revealed that fragrance composition influenced impressions of personality. Impressions made of affiliated fragrances (oriental and chypre) were more closely aligned than impression of the dissimilar (floral) fragrance for the multi-item Uninhibited and Traditional Male factors and single item traits such as aggressive, confident, and assertive according to Tukey's tests. The floral fragrance produced significantly (p<.05) lower ratings in these instances. The findings suggest that compositional components of fragrances (olfactory cues) were used in formation of impressions. This has implications for research of the role of olfactory cues in social and professional interactions.