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| Poster #200 A natural lesion model unravels the nature of chemical fear communication |
| Jasper H.B. de Groot Behavioural Science Institute, Radboud University, Nijmegen, --, Netherlands |
Debunking the human tiny smeller myth, scientific research has revealed that humans have excellent smell abilities, including social communication. Studies show that humans convey adaptive social information, such as emotions, through body odor, synchronizing senders and receivers via behavioral, affective, and neural responses. However, the question of whether humans use pheromones—species-wide chemical signals that trigger innate responses—for social communication remains unresolved, presenting a multidisciplinary challenge beyond the scope of psychology. To investigate this, we combined insights from chemical analyses of fear odors with a study of patients with Urbach-Wiethe Disease (UWD), an extremely rare, recessive genetic condition marked by basolateral amygdala (BLA) calcification, while other brain regions remain intact. Notably, BLA damage causes hyper-responsiveness to unconditioned fear stimuli and impaired fear learning, making UWD a unique natural lesion model to examine whether human chemical communication relies more on innate or learned mechanisms. In South Africa, where UWD is more prevalent, we established a custom-built lab space with an airport-transportable olfactometer. A double-blind within-subjects experiment was conducted with 5 UWD patients and 14 controls matched on age, gender, IQ, and smell ability. Participants smelled three odors—fear (synthesized molecules from chemical analysis), disgust (isovaleric acid, resembling sweat), and neutral (odorless air)—while classifying morphed faces (35% to 65% fear-disgust continuum). Results revealed a significant and strong hyperfear-perception bias in UWD patients (Cohen’s d = 1.15), highlighting that fear odor could be synthesized and that the BLA has a critical role in potentially innate human chemical communication. |