Detecting snakes is literally built into our visual cortex.

Human visual processing appears to have a hardwired bias for detecting snakes, particularly in the lower visual field. Evolutionary theories suggest this stems from the survival advantage of quickly spotting snakes, which posed a significant threat to early humans. Research, like that from Isbell (2006), points to the "Snake Detection Theory," arguing that primates developed enhanced visual sensitivity to snake-like patterns—such as horizontal, sinuous shapes—due to predation pressure. Studies (e.g., Van Le et al., 2013) show faster detection of snake images in the lower visual field, where snakes are more likely to appear in natural environments. This is supported by neuroscientific evidence indicating the amygdala responds rapidly to snake-like stimuli, even before conscious awareness.