Snakes elicit specific neural responses in the human infant brain

Abstract

Detecting predators is essential for survival. Given that snakes are the first of primates' major predators, natural selection may have fostered efficient snake detection mechanisms to allow for optimal defensive behavior. Here, we provide electrophysiological evidence for a brain-anchored evolved predisposition to rapidly detect snakes in humans, which does not depend on previous exposure or knowledge about snakes. To do so, we recorded scalp electrical brain activity in 7-to 10-month-old infants watching sequences of flickering animal pictures. All animals were presented in their natural background. We showed that glancing at snakes generates specific neural responses in the infant brain, that are higher in amplitude than those generated by frogs or caterpillars, especially in the occipital region of the brain. The temporal dynamics of these neural responses support that infants devote increased attention to snakes than to non-snake stimuli. These results therefore demonstrate that a single fixation at snakes is sufficient to generate a prompt and large selective response in the infant brain. They argue for the existence in humans of an inborn, brain-anchored mechanism to swiftly detect snakes based on their characteristic visual features.

Fast Detection of Snakes and Emotional Faces in the Macaque Amygdala

“…In the present study, all visual stimuli were similarly presented to the monkeys only during training and recording sessions. Therefore, the differences in responses among the eight categories are likely to be attributed to their innate biological significance, consistent with previous studies reporting that behavioral responses to snakes and faces are innate in monkeys (for snakes: Nelson et al, 2003 ; Kawai and Koda, 2016 ; Bertels et al, 2020 ; for faces: Sackett, 1966 ; Sugita, 2008 ). However, previous studies also reported that behavioral responses to these stimuli may be altered by prior experience: macaque monkeys developed a fear of snakes by observational learning ( Cook and Mineka, 1990 ), and stressful early life experience of parents of subjects might alter coping styles of the subjects in response to snakes in marmosets ( Clara et al, 2008 ).…”

“…Growing evidence consistently supports this. For example, naïve monkeys and humans detect snakes more quickly than other objects under a variety of conditions ( Nelson et al, 2003 ; Kawai and Koda, 2016 ; Bertels et al, 2020 ).…”

Titi monkey neophobia and visual abilities allow for fast responses to novel stimuli

“…Vocalizations elicited by snakes draw conspecifics to the location of the snakes, allowing them to learn about the presence of a potential danger and become more vigilant themselves [13][14][15] . In addition, laboratory studies using different methods have consistently shown that both human and non-human primates visually detect snakes more quickly or attend to them longer than other stimuli, including animate stimuli such as spiders, frogs, caterpillars, and birds [ [16][17][18][19][20][21][22] ; earlier studies reviewed in 23 ]. Images of snakes also stimulate more neuronal activity as well as faster and stronger responses in an area of the macaque brain involving attention compared to images of raptors and felids, the two other main classes of predators of primates 24 .…”

Mechanisms of False Alarm in Response to Fear Stimulus: An Event-Related Potential Study

“…Studies have proven that snakes were a typical representation of fear (Isbell, 2006;Erlich et al, 2013;Coelho et al, 2021). This study used previous research methods to induce fear by taking pictures of snakes (Langeslag and van Strien, 2018;Masataka et al, 2018;Beligiannis and Van Strien, 2019;Bertels et al, 2020). In view of the fact that the object of False Alarm must be "similar to the real fear object but not physically threatening, " toy snakes similar to a real snake were selected as the object of False Alarm, and the mechanisms underlying False Alarm were revealed by comparing cognitive processing similarities and differences between the two types of stimuli.…”