The Subtle Signaling Strength of Smells: A Masked Odor Enhances Interpersonal Trust

Abstract

Most everyday smells, from lavender to body odors, are complex odorant mixtures that “host” particular compounds that guide (social) behavior and motivation (biomarkers). A key element of social behavior is interpersonal trust, and building on previous research showing that (i) lavender odor can enhance trust, and that (ii) certain compounds in body odor can reduce stress in mice and humans (called “social buffering”), we examined whether a grassy-smelling compound found in both body odors and lavender, hexanal, would enhance interpersonal trust. Notably, we applied odor masking to explore whether trust could be influenced subconsciously by masked (i.e., undetectable) hexanal. In Study 1 (between-subjects), 90 females played a Trust Game while they either smelled hexanal (0.01% v/v), clove odor (eugenol: 10% v/v), or hexanal masked by clove odor (a mix of the former). As a sign of higher trust, participants gave more money to a trustee while exposed to masked hexanal (vs. the mask: eugenol). In Study 2 (within-subjects, double-blind), another sample of 35 females smelled the same three odors, while they rated the trustworthiness of a spectrum of faces that varied on trustworthiness. Controlling for subjective odor intensity and pleasantness and substantiating that masked hexanal could not be distinguished from the mask, faces were perceived as more trustworthy during exposure to masked hexanal (vs. the mask: eugenol). Whereas non-masked hexanal also increased face trustworthiness ratings, these effects disappeared after controlling for the odor’s subjective intensity and pleasantness. The combined results bring new evidence that trust can be enhanced implicitly via undetected smells.

Olfaction in the Multisensory Processing of Faces: A Narrative Review of the Influence of Human Body Odors

“…Translated to olfactory issues, exposure to pleasant body odors (male axillary sweat) induced trustworthiness attribution in a Trust Game (Lobmaier et al, 2020), whereby participants gave more money to a trustee during the game. Similar findings were reported in women following exposure to an isolated component of human body effluvium (i.e., hexanal;van Nieuwenburg et al, 2019). Implicit exposure to hexanal not only affected interpersonal attribution of trust in a Trust Game, but also increased face trustworthiness ratings (van Nieuwenburg et al, 2019).…”

“…Similar findings were reported in women following exposure to an isolated component of human body effluvium (i.e., hexanal;van Nieuwenburg et al, 2019). Implicit exposure to hexanal not only affected interpersonal attribution of trust in a Trust Game, but also increased face trustworthiness ratings (van Nieuwenburg et al, 2019). The influence of the odorant on face trustworthiness ratings was particularly evident when presented outside of conscious awareness, thus ruling out an effect merely based on differences in odor intensity or pleasantness.…”

From sterile labs to rich VR: Immersive multisensory context critical for odors to induce motivated cleaning behavior

“…Statistical analysis Outliers: For cleaning task parameters (not standardized), outliers were identified with the most robust scale measure in the presence of outliers, namely values surpassing three median absolute deviation (MAD) units (Leys, Ley, Klein, Bernard, & Licata, 2013). When outliers were identified, their values were changed to be one unit on that variable's scale above the next extreme score on that variable that was not an outlier (Field, 2009, p. 153;Field, 2013, p. 198), a procedure also used in our previous research (e.g., Kamiloglu, Smeets, de Groot, & Semin, 2018;van Nieuwenburg, de Groot, & Smeets, 2019). As sniffing data were standardized per subject and per odor, outlier analysis was deemed unnecessary.…”

Effect of scent on comfort of aircraft passengers

“…People are more prosocial and willing to help others in the environment with pleasant ambient fragrance [18]. Trust can also be enhanced implicitly via undetected smells [19].…”