Abstract
Snakes have provided a serious threat to primates throughout evolution. Furthermore, bites by venomous snakes still cause significant morbidity and mortality in tropical regions of the world. According to the Snake Detection Theory (SDT Isbell, 2006; 2009), the vital need to detect camouflaged snakes provided strong evolutionary pressure to develop astute perceptual capacity in animals that were potential targets for snake attacks. We performed a series of behavioral tests that assessed snake detection under conditions that may have been critical for survival. We used spiders as the control stimulus because they are also a common object of phobias and rated negatively by the general population, thus commonly lumped together with snakes as “evolutionary fear-relevant”. Across four experiments (N = 205) we demonstrate an advantage in snake detection, which was particularly obvious under visual conditions known to impede detection of a wide array of common stimuli, for example brief stimulus exposures, stimuli presentation in the visual periphery, and stimuli camouflaged in a cluttered environment. Our results demonstrate a striking independence of snake detection from ecological factors that impede the detection of other stimuli, which suggests that, consistent with the SDT, they reflect a specific biological adaptation. Nonetheless, the empirical tests we report are limited to only one aspect of this rich theory, which integrates findings across a wide array of scientific disciplines.
Highlights
In his classic treatise on ‘‘The expression of the emotions in man and animals’’, Darwin [1] recognized snakes as an important evolutionary threat to humans and other primates
As shown by the significant interaction between target and exposure time, F (4, 204)519.54, p,.0001, the results confirmed our hypothesis that the detection of snakes was faster than that of spiders and mushrooms at the shortest stimulus duration, independently on the number of distractor stimuli
In addition to the reliable interaction between stimuli and exposure duration described in the article, there were several other reliable effects in the ANOVAs
Summary
In his classic treatise on ‘‘The expression of the emotions in man and animals’’, Darwin [1] recognized snakes as an important evolutionary threat to humans and other primates. The emphasis on snakes as a central agent in primate evolution proposed by the SDT [8] provides a novel theoretical rationale for expecting differential effects of snakes and spiders both on human visual attention and defensive behaviors. Because spiders primarily prey on insects rather than mammals [29], the case for an evolutionary origin of spider fear is clearly weaker than that for snakes They are ideal comparison stimuli for testing the SDT. The results showed that snakes more potently capture attention than spiders (and mushrooms) under high perceptual load conditions [34] Those preliminary studies were designed to open the avenue for the extensive behavioral testing presented in the present study. Our experimental work focused on factors such as stimulus duration, foveal versus peripheral vision, the complexity of the display as indicated by number of distracting items, and top-down versus bottom-up control of attention, which correspond to ecological conditions thought to be important for snake detection [8]
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
