An ability to detect threatening stimuli more efficiently than nonthreatening stimuli.
People are born with automatic visual detection mechanisms for evolutionarily threatening stimuli, such as snakes. These fearful stimuli are detected more quickly than nonthreatening stimuli and are thought to have evolutionary origins; efficiently detecting threats, no doubt provided a selective advantage for our human ancestors.
For example, when presented with images containing threatening elements, such as spiders, and non-threatening elements, such as flowers, people can locate the sinister parts more quickly than the non-threatening- elements. The search times are not affected by the location of the sinister element or the number of distracters surrounding the element. Similarly, people can locate an angry face in a group of happy or sad faces more quickly than a happy or sad face in a group of angry faces. The ability to detect evolutionarily threatening stimuli is a function of perceptual processes that automatically scan the visual field below the level of conscious awareness. Unlike conscious processing, which is relatively slow and serial, threat detection occurs quickly and parallel with other visual and cognitive processes
Almost anything possessing the key threat features of snakes, spiders, and angry faces can trigger the threat detection mechanism, such as the wavy line of a snake, the thin legs and sizeable circular body of spiders, and the V-shaped eyebrows of an angry face. Given their evolutionary relevance, it is reasonable that other general predatory features (e.g., forward-looking eyes) will also trigger the threat-detection mechanism. Still, little research of this type has been conducted. In any event, the sensitivity to certain threat features explains why twigs and garden hoses often frighten young children and why people have a general fear of insects that superficially resemble spiders (e.g., roaches). When people have conscious fears or phobias of threatening stimuli, the threat detection ability is more sensitive, and search times for threatening stimuli are further reduced. Once attention is captured, fearful stimuli are also better at holding attention than nonthreatening stimuli.
Consider threatening stimuli to rapidly attract attention and imply threat or foreboding (e.g., designs of markers to keep people away from an area). Abstracted representations of threat features can trigger threat-detection mechanisms without the accompanying adverse emotional reaction. Therefore, consider such elements to attract attention in noisy environments, such as a dense retail shelf display. Achieving a balance between maximum detectability and minimal adverse effect is more art than science, and therefore should be explored with caution and verified with testing on the target audience.
See also Baby-Face Bias, Freeze-Flight-Flight-Forfeit, Inattentional Blindness, and Red Effect.