The social odor scale: Development and initial validation of a new scale for the assessment of social odor awareness

The degree of attention individuals pay to olfactory cues (called odor awareness) influences the role of odors in everyday life. Particularly, odors produced by the human body (i.e., social odors) are able to carry a wide variety of information and to elicit a broad spectrum of emotional reactions, making them essential in interpersonal relationships. Hence, despite the assessment of awareness toward social odors is crucial, a proper tool is still lacking. Here, we designed and initially validated the Social Odor Scale (SOS), a 12-item scale designed to measure the individual differences in awareness towards different social odors. In Study 1, an exploratory factor analysis (EFA; KMO test: MSA = 0.78; Bartlett’s test: χ2(78) = 631.34, p < 0.001; Chi-squared test: χ2(42) = 71.84, p = 0.003) suggests that the three factors structure was the model that best fit with the Italian version of the scale. The confirmatory factor analysis (CFA) supports a second-order model with one higher-order factor representing social odor awareness in general and three lower-order factors representing familiar, romantic partner, and stranger social odors. The final version of the scale presented a good fit (RMSEA = 0.012, SRMR = 0.069, CFI = 0.998, TLI = 0.997). In Study 2, CFA was performed in the German version of the scale confirming the validity of scale structure. Study 3 and 4 revealed that SOS total score and its subscales were positively correlated with other validated olfactory scales, but not with olfactory abilities. Moreover, SOS was found to be related to the gender of the participants: women reported to be more aware to social odors and, specifically, to familiar social odors than men. Overall, the results indicated that SOS is a valid and reliable instrument to assess awareness toward social odors in everyday life.

Coding of social odors in the hippocampal CA2 region as a substrate for social memory

The ability to encode and update information about individuals is critical for lasting social relationships. Although the hippocampus is important for social recognition memory, its underlying neural representations remain elusive. Here we investigate the neural codes mediating social recognition and learning by examining social odor recognition and associative odor-reward learning in mice. We performed high-resolution calcium imaging from the hippocampal CA2 region of awake head-fixed mice, as CA2 is necessary for social recognition memory. We find that CA2 encodes specific neural representations of novel social odors that are further refined during associative odor-reward learning. Optogenetic silencing of CA2 impairs the formation of reward associations. Furthermore, CA2 population activity represents odors in a geometry that enables abstract representations of social versus non-social odors. Thus, CA2 distinguishes multiple forms of olfactory stimuli to enhance the learning of social odors and associations, which are poised to serve as substrates of social memory.

The Social Odor Scale: development and validation of a new scale for the assessment of Social Odor Awareness

The degree of attention individuals pay to olfactory cues (called odor awareness) influence the role of odors in everyday life. Particularly, odors produced by the human body (i.e., social odors) are able to carry a wide variety of information and to elicit a broad spectrum of emotional reactions, making them essential in interpersonal relationships. Hence, despite the assessment of awareness toward social odors is crucial, a proper tool is still lacking. Here, we designed and validated the Social Odor Scale (SOS), a measure to assess the individual differences in awareness towards different social odors. In Study 1, an exploratory factor analysis (EFA) supports the initially developed four factor structure of the Italian version of the scale. In Study 2, EFA was performed in the German version of the scale confirming the validity of scale structure. Finally, a confirmatory factor analysis (Study 4) corroborates the construct validity of the SOS and its subscales. Hence, the final version of SOS is composed of 16 items, four for each subscale: own, familiar, romantic partner, and stranger social odors. Study 3 and 4 revealed that SOS total score and its subscales were positively correlated with other validated olfactory scales, but not with olfactory abilities. Moreover, SOS was found to reflect the inter-individual variability that characterize social odor processing: SOS was related to age, gender and reproductive state of the participants. Overall, the results indicated that SOS is a valid and reliable instrument to assess awareness toward social odors in everyday life.

Social odors (even when masked) make you more emotional: behavioral and neural insights

Moral rules evolved within specific social contexts that are argued to shape moral choices. In turn, moral choices are hypothesized to be affected by social odors as they powerfully convey socially-relevant information. We thus investigated the neural underpinnings of the effects that social odors operate on the participants’ decisions. In an fMRI study we presented to healthy individuals 64 moral dilemmas divided in incongruent (real) and congruent (fake) moral dilemmas, using different types of harm (intentional: instrumental dilemmas, or inadvertent: accidental dilemmas). Participants were required to choose between deontological or utilitarian actions under the exposure to a neutral fragrance (masker) or social odors concealed by the same masker. Smelling the masked social odor while processing incongruent (but not congruent) dilemmas activates the supramarginal gyrus, consistent with an increase in prosocial attitude. When processing accidental (but not instrumental) dilemmas, smelling the social odor activates the angular gyrus, an area associated with the processing of people’s presence, supporting the hypothesis that social odors enhance the saliency of the social context in moral scenarios. These results suggest that social odors can influence moral choices by increasing the emotional experience during the decision process, and further explain how sensory unconscious biases influence human behavior.

Do females influence paternal responsiveness in male prairie voles Microtus ochrogaster by increasing the salience of infant odors?

Male prairie voles become more responsive to infants following cohabitation with a female. Exposure to female sensory cues prior to offspring birth may influence male paternal tendencies by modifying his response to infant odors in particular or to odors in general. To test these hypotheses, males were housed with an unfamiliar female or a same-sex sibling for 13 days then examined for their response towards either live infants or infant-like inanimate objects covered with one of three odors: water, infant, sub-adult. We recorded the number of males that retrieved and manipulated the infants or odor-covered objects and measured the frequency and duration of time males spent attending to them or engaged in other non-social activities. Female-Cohabited males approached the container holding infant-odor covered objects faster than Male-Cohabited males, but showed no differences in time spent manipulating those objects. Males in both groups spent more time manipulating live infants than odor-covered objects. However, Female-Cohabited subjects were more likely to manipulate odor-covered objects as well as live infants than Male-Cohabited subjects. Additionally, the frequency of self-grooming in Female-Cohabited males was higher for water-covered objects compared to Male-Cohabited males. In presence of water and live infants, Female-Cohabited males groomed themselves with greater frequency than in presence of infant odor or sub-adult odor. The data suggest that female cues increase the male’s sensitivity to infant odors and enhance the salience of non-social odors.