Venomous snakes elicit stronger fear than nonvenomous ones: Psychophysiological response to snake images

Abstract

Snakes have been important ambush predators of both primates and human hunter-gatherers throughout their co-evolutionary history. Viperid snakes in particular are responsible for most fatal venomous snakebites worldwide and thus represent a strong selective pressure. They elicit intense fear in humans and are easily recognizable thanks to their distinctive morphotype. In this study, we measured skin resistance (SR) and heart rate (HR) in human subjects exposed to snake pictures eliciting either high fear (10 venomous viperid species) or disgust (10 nonvenomous fossorial species). Venomous snakes subjectively evaluated as frightening trigger a stronger physiological response (higher SR amplitude) than repulsive non-venomous snakes. However, stimuli presented in a block (more intense stimulation) do not trigger a stronger emotional response compared to sequentially presented stimuli (less intense stimulation). There are significant interindividual differences as subjects with high fear of snakes confronted with images of viperid snakes show stronger, longer-lasting, and more frequent changes in SR and higher HR compared to low-fear subjects. Thus, we show that humans demonstrate a remarkable ability to discriminate between dangerous viperids and harmless fossorial snakes, which is also reflected in distinct autonomous body responses.

The Ultimate List of the Most Frightening and Disgusting Animals: Negative Emotions Elicited by Animals in Central European Respondents

“…Given the fact that many snakes can be deadly, it would probably be advantageous to generalize and fear all the snakes the same rather than taking a risk of being bitten by a venomous snake. However, recent studies have shown that not all snakes are perceived as one category in terms of experienced emotions (not only fear, but also disgust; see below [ 23 , 57 ]. Some snake morphotypes are feared more than others.…”

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

“…This may also be reflected behaviorally. Capuchins do not head-cock to models of snakes or novel stimuli 26 , they react similarly to two- and three-dimensional images, and, like macaques and humans, they are able to distinguish between dangerous and non-dangerous snakes 26 , 32 , 72 , 73 , an ability that undoubtedly requires excellent visual discrimination. Capuchins are the most terrestrial of platyrrhines, and the risk from terrestrial as well as arboreal venomous snakes may have put a premium on excellent vision for objects that are close by and in front of oneself.…”

Attentional, emotional, and behavioral response toward spiders, scorpions, crabs, and snakes: Do they all scare us?

“…However, we do not think that this result should be generalized to the population level as it is most probably a by-product of the experimental design (see also [28]). On the one hand, a high fear rating of snake stimuli should be expected since they were all highly venomous vipers [10,24,56]. On the other hand, to spider-fearful participants, spiders are the most salient stimuli no matter the objective dangerousness of others and therefore snakes are rated as less frightening in comparison.…”

“…Snakes were also shown to be detected faster than other animals in visual search tasks using an eyetracking camera [21,22], even in suboptimal visual conditions [23]. Venomous snakes also evoked elevated psychophysiological responses [24]. Recently, coevolution between snakes and primates was illustrated in an example of snake venom and resistance to it in primates [25].…”