Other Types of Studies Showing that Snakes Hold Special Status in Threat Perception

Abundant evidence has shown that human and nonhuman primates have perceptual biases for rapid detection of evolutionarily fear-relevant stimuli (snakes) in terms of threat perception using the visual search paradigm. There are, however, several levels at which one can criticize these paradigms. In this chapter, I summarize the problems with visual search studies. Then, I explore electroencephalogram studies using the early posterior negativity (EPN), an event-related potential (ERP) component that reflects early selective visual processing of emotionally significant information, which increases when evolutionarily relevant threat stimuli are presented. Some studies have found that EPN amplitudes in response to snake images are larger than are those for spider or crocodile images. This larger EPN for snakes is interpreted as increased source activity in visual areas, as projected from the amygdala by triggering fear circuits. Of course, this projection route confers a significant advantage for primates to rapidly respond to potential risks, helping them to evolve efficiently. These results suggest that humans are predisposed to attend rapidly to snakes through our evolutionary lineage and confirm that spiders do not appear to hold special early attentional value.