Revisiting the fear of snakes in children: the role of aposematic signalling.

Jérémie Souchet,Fabien Aubret

doi:10.1038/srep37619

Abstract

Why humans fear snakes is an old, yet unresolved debate. Its innate origin from evolutionary causes is debated against the powerful influence early experience, culture, media and religion may have on people’s aversion to snakes. Here we show that the aversion to snakes in human beings may have been mistaken for an aversion to aposematic signals that are commonly displayed by snakes. A total of 635 children were asked to rate single item images as “nice” or “mean”. Snakes, pets and smiley emoticon items were not rated as “mean” unless they displayed subtle aposematic signals in the form of triangular (rather than round) shapes. Another 722 children were shown images featuring two items and asked which item was “nice” and which item was “mean”. This context dependent comparison triggered even sharper responses to aposematic signals. We hypothesise that early primates evolved an aversion for aposematic signals in the form of potentially harmful triangular shapes such as teeth, claws or spikes, not for snakes per se. Further, we hypothesise that this adaptation was in turn exploited by snakes in their anti-predatory threat display as a triangular head or dorsal zig-zag pattern, and is currently the basis for efficient international road-danger signalling.

Highlights

Snakes are one of the most common subjects of intense fears and phobias in humans[1,2,3,4,5]
Tests were designed to assess the raw perception of children of a single item image (Fig. 1A to D) as either nice or mean; and of double item images (Fig. 1E to H) in order to trigger a context-dependant response
Our tests with single and double item images demonstrated that the decision process in the vast majority of children was influenced by the presence of aposematic signalling: snakes, pets and smiley emoticon images were overall rated as “nice” unless they displayed one or two subtle aposematic signals in the form of triangular shapes

Summary

Introduction

Snakes are one of the most common subjects of intense fears and phobias in humans[1,2,3,4,5]. Some authors suggested that an evolutionary arms race between early constrictor snakes and mammals triggered the development of orbital convergence, visual specialisation, and brain expansion in early primates; and incidentally the current human reactions observed in response to the appearance of venomous snakes (viperids and elapids[3,4,8]). Detecting and avoiding venomous snakes may have contributed to survival of early humans and primates While ambush predators such as vipers need to be invisible to their prey, they have evolved a number of traits to either deter potential predators or to avoid being trampled, such as warning or aposematic signals. How human beings detect and assess aposematic signals has, to our knowledge, not been explored and could hold the key to our current (mis)understanding of snake fear and phobia. Tests were designed to assess the raw perception of children of a single item image (Fig. 1A to D) as either nice or mean (listen to S2 single item image); and of double item images (Fig. 1E to H) in order to trigger a context-dependant response (i.e. children were asked to indicate which of the two items was nice and which was mean – listen to S2 double item image)

Methods

Results

Conclusion