PATHOLOGICAL FEAR OF GUNS SKIN
The ability to recognize danger presented by a snake by only a pictured skin detail was also observed in Vervet monkeys ( Isbell and Etting, 2017), and Capuchin monkeys were able to recognize whether the presented snake was dangerous or harmless only based on the skin pattern ( Meno et al., 2013). Souchet and Aubret (2016) proposed that venomous snakes adopt this phenomenon and use contrasting patterns and morphology with sharp edges as an aposematic signal to deter enemies and communicate their dangerousness. Moreover, some naturally occurring shapes and patterns are perceived negatively, and processed faster than other patterns, such as sharp edges ( Guthrie and Wiener, 1966 Bar and Neta, 2006, 2007), zig zag patterns ( Üher, 1991), or strong contrasting patterns in general ( Näsänen et al., 2001). The human brain reacts much faster to pictures of snake skin than similarly, colored bird feathers ( van Strien and Isbell, 2017). However, recent research has shown that the pattern of snake scales is also important. LoBue and Deloache (2011) provide evidence that it is the distinctive coiled snake morphology that attracts prioritized human attention. Moreover, EEG studies show that neural processing of snake stimuli is prioritized when compared to other animals such as spiders and birds ( van Strien et al., 2014). Among evolutionarily irrelevant (neutral) stimuli, snake pictures act as strong distractors ( Soares et al., 2009a) and are detected faster ( LoBue and Deloache, 2011 Soares et al., 2014) than, for example, flowers and mushrooms, but not faster than stimuli of modern threats such as guns ( Fox et al., 2007 Zsido et al., 2018b). These illustrations are included in the study and may be freely used as a standardized assessment tool when investigating the role of fear and disgust in human emotional response to snakes.ĭue to a long co-evolutionary history with snakes, both humans and non-human primates evolved specific neural mechanisms for rapid snake recognition ( Isbell, 2006 LoBue and DeLoache, 2008 Öhman et al., 2012 Van Le et al., 2013 Baynes-Rock, 2017). A new set of subjects ( n = 104) sorted these snakes and confirmed that the illustrated snakes evoked the same discrete emotions as their photographic counterparts. Third, we randomly selected 20 species (10 fear-evoking and 10 disgust-evoking) out of the previous set and had them professionally illustrated. The results showed that the fear-evoking and disgust-evoking snakes fit mainly into their respective groups. Another set of respondents ( n = 172) sorted the set, once according to perceived fear and the second time according to perceived disgust. Second, to create stimuli evoking a discrete emotional response, we developed a picture set consisting of 40 snakes with exclusively fear-eliciting and 40 snakes with disgust-eliciting features. We then identified the specific traits contributing to the perception of fear (large body size, expressive scales with contrasting patterns, and bright coloration) and disgust (thin body, smooth texture, small eyes, and dull coloration). Snakes rated as the most fear-evoking were from the family Viperidae ( Crotalinae, Viperinae, and Azemiopinae), while the ones rated as the most disgusting were from the group of blind snakes called Typhlopoidea ( Xenotyphlopinae, Typhlopinae, and Anomalepidinae).
First, two independent groups of respondents evaluated 45 images covering most of the natural variability of snakes and rated responses to either perceived fear ( n = 175) or disgust ( n = 167). We designed three-step-selection experiments to identify prototypical snake species evoking exclusively fear or disgust. Different snakes may evoke fear or disgust in humans, or even both emotions simultaneously. However, snake species differ in their true level of danger and are highly variable in appearance despite the uniform legless form.
Humans perceive snakes as threatening stimuli, resulting in fast emotional and behavioral responses.
2Department of Zoology, Faculty of Science, Charles University, Prague, Czechia.1National Institute of Mental Health, Klecany, Czechia.
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