ABSTRACT
Aversive stimuli are those events that organisms evade, avoid, or escape from. Stings, attacks, foul odors, bright light, and very loud noises are examples of events that organisms are prepared to evade on the basis of phylogeny. Escaping or avoiding these primary aversive stimuli had survival value, presumably because those animals that emitted this behavior survived and reproduced. In other words, organisms do not learn that these stimuli are aversive; they are biologically prepared to avoid or escape such events.
