Signaalstimuli

Signaalstimuli, in ethology, are environmental cues that trigger a specific, often innate, behavioral response in animals. They act as releasing signals for fixed action patterns (FAPs), sequences of behavior that run to completion once initiated. The concept, associated with Niko Tinbergen and colleagues, emphasizes that certain simple features of a stimulus can disproportionately drive behavior, even when the rest of the sensory context is variable.

Signaalstimuli are typically characterized by their ecological relevance and their minimal informational content: a small, salient cue, such as a red patch on a rival, the shape of a beak or comb, or a parental egg outside the nest. When detected, the cue elicits a stereotyped response that is relatively resistant to learning and context, though it can be modulated by internal state or prior experience. The released response is called a fixed action pattern.

Common examples include the red belly of male stickleback fish triggering aggression in conspecifics, or an egg outside a goose's nest provoking egg-rolling behavior despite other distractions. Not all stimuli act as signaalstimuli; many responses arise from learned associations or more general arousal. Signaalstimuli are central to understanding innate behavior and the evolution of signaling systems in animals, and they inform comparative studies of perception, decision-making, and the neural basis of behavior.