Assessing Personality Using Body Odor: Differences Between Children and Adults

Many studies have demonstrated that smell is an important sense in social interactions, and recently it was determined that olfactory cues might also convey information concerning certain personality traits. The present study investigated whether personality traits might be recognized using olfactory cues in contexts other than male-female interactions. 75 children (35 girls and 40 boys, M = 8.29 years) and 75 young adults (41 women and 34 men, M = 20.5 years) rated the personality traits of 50 unknown individuals (24 women and 26 men, M = 24.02 years) based on their body odor. The correlations between scent ratings and the self-assessed personality dimensions of odor donors were analyzed. The results show that both children and adults assess neuroticism relatively accurately, whereas only adults recognized dominance. These results suggest that olfaction supplements visual and auditory cues throughout our whole lives, contributing to the first impression accuracy of certain personality traits.

Human gender differences in the perception of conspecific alarm chemosensory cues

It has previously been established that, in threatening situations, animals use alarm pheromones to communicate danger. There is emerging evidence of analogous chemosensory "stress" cues in humans. For this study, we collected alarm and exercise sweat from "donors," extracted it, pooled it and presented it to 16 unrelated "detector" subjects undergoing fMRI. The fMRI protocol consisted of four stimulus runs, with each combination of stimulus condition and donor gender represented four times. Because olfactory stimuli do not follow the canonical hemodynamic response, we used a model-free approach. We performed minimal preprocessing and worked directly with block-average time series and step-function estimates. We found that, while male stress sweat produced a comparably strong emotional response in both detector genders, female stress sweat produced a markedly stronger arousal in female than in male detectors. Our statistical tests pinpointed this gender-specificity to the right amygdala (strongest in the superficial nuclei). When comparing the olfactory bulb responses to the corresponding stimuli, we found no significant differences between male and female detectors. These imaging results complement existing behavioral evidence, by identifying whether gender differences in response to alarm chemosignals are initiated at the perceptual versus emotional level. Since we found no significant differences in the olfactory bulb (primary processing site for chemosensory signals in mammals), we infer that the specificity in responding to female fear is likely based on processing meaning, rather than strength, of chemosensory cues from each gender.

Chemosignals communicate human emotions

Can humans communicate emotional states via chemical signals? In the experiment reported here, we addressed this question by examining the function of chemosignals in a framework furnished by embodied social communication theory. Following this theory, we hypothesized that the processes a sender experiences during distinctive emotional states are transmitted to receivers by means of the chemicals that the sender produces, thus establishing a multilevel correspondence between sender and receiver. In a double-blind experiment, we examined facial reactions, sensory-regulation processes, and visual search in response to chemosignals. We demonstrated that fear chemosignals generated a fearful facial expression and sensory acquisition (increased sniff magnitude and eye scanning); in contrast, disgust chemosignals evoked a disgusted facial expression and sensory rejection (decreased sniff magnitude, target-detection sensitivity, and eye scanning). These findings underline the neglected social relevance of chemosignals in regulating communicative correspondence outside of conscious access.

Does Personality Smell? Accuracy of Personality Assessments Based on Body Odour

People are able to assess some personality traits of others based on videotaped behaviour, short interaction or a photograph. In our study, we investigated the relationship between body odour and the Big Five personality dimensions and dominance. Sixty odour samples were assessed by 20 raters each. The main finding of the presented study is that for a few personality traits, the correlation between self–assessed personality of odour donors and judgments based on their body odour was above chance level. The correlations were strongest for extraversion (.36), neuroticism (.34) and dominance (.29). Further analyses showed that self–other agreement in assessments of neuroticism slightly differed between sexes and that the ratings of dominance were particularly accurate for assessments of the opposite sex. Copyright © 2011 John Wiley & Sons, Ltd.

Adrenarche and middle childhood

Middle childhood, the period from 6 to 12 years of age, is defined socially by increasing autonomy and emotional regulation, somatically by the development of anatomical structures for subsistence, and endocrinologically by adrenarche, the adrenal production of dehydroepiandrosterone (DHEA). Here I suggest that DHEA plays a key role in the coordinated development of the brain and body beginning with middle childhood, via energetic allocation. I argue that with adrenarche, increasing levels of circulating DHEA act to down-regulate the release of glucose into circulation and hence limit the supply of glucose which is needed by the brain for synaptogenesis. Furthermore, I suggest the antioxidant properties of DHEA may be important in maintaining synaptic plasticity throughout middle childhood within slow-developing areas of the cortex, including the insula, thamalus, and anterior cingulate cortex. In addition, DHEA may play a role in the development of body odor as a reliable social signal of behavioral changes associated with middle childhood.

Role of gut nutrient sensing in stimulating appetite and conditioning food preferences

The discovery of taste and nutrient receptors (chemosensors) in the gut has led to intensive research on their functions. Whereas oral sugar, fat, and umami taste receptors stimulate nutrient appetite, these and other chemosensors in the gut have been linked to digestive, metabolic, and satiating effects that influence nutrient utilization and inhibit appetite. Gut chemosensors may have an additional function as well: to provide positive feedback signals that condition food preferences and stimulate appetite. The postoral stimulatory actions of nutrients are documented by flavor preference conditioning and appetite stimulation produced by gastric and intestinal infusions of carbohydrate, fat, and protein. Recent findings suggest an upper intestinal site of action, although postabsorptive nutrient actions may contribute to flavor preference learning. The gut chemosensors that generate nutrient conditioning signals remain to be identified; some have been excluded, including sweet (T1R3) and fatty acid (CD36) sensors. The gut-brain signaling pathways (neural, hormonal) are incompletely understood, although vagal afferents are implicated in glutamate conditioning but not carbohydrate or fat conditioning. Brain dopamine reward systems are involved in postoral carbohydrate and fat conditioning but less is known about the reward systems mediating protein/glutamate conditioning. Continued research on the postoral stimulatory actions of nutrients may enhance our understanding of human food preference learning.

Olfactory abnormalities in anxiety disorders

The olfactory system plays an important role in both animal and human anxiety reactions. However, results on olfactory performance during the course of clinical anxiety disorders remain scarce. Therefore, we conducted an exploratory pilot study in 17 patients currently diagnosed with an anxiety disorder. Patients participated in olfactory and psychological testing and were compared to 17 healthy controls. Statistical analyses revealed significant deficits concerning olfactory discrimination in patients, while no changes in threshold and identification ability occurred. Most interestingly, patients showed higher intensity estimates and an increased rating range concerning olfactory hedonic judgements. Results are discussed in light of prior findings and related to neural correlates of olfactory perception and anxiety reactions.