[[File:3-spined_stickleback.jpg|alt=|thumb|A 3-spined stickleback like those used in Tinbergen's experiments.]]
One example of fixed action patterns is the courtship and aggression behaviors of the male [[stickleback]], particularly the [[Three-spined stickleback|three-spined stickleback]], during mating season, described in a series of studies by Niko Tinbergen.<ref name=":82"/><ref name=":2">{{cite journal |last1=Rowland |first1=William |title=Habituation and development of response specificity to a sign stimulus: male preference for female courtship posture in stickleback |journal=Animal Behaviour |date=February 3, 2000 |volume=60 |issue=1 |pages=63–68 |accessdate=|doi=10.1006/anbe.2000.1462 |pmid=10924204 |s2cid=23095310 }}</ref> During the spring mating season, male sticklebacks ventrum turns red and they establish a territory to build a nest.<ref name=":82"/> They attack other male sticklebacks that enter their territory, but court females and entice them to enter the nest to lay their eggs.<ref name=":82"/> Tinbergen used models of sticklebacks to investigate which features of male and female sticklebacks elicited attack and courtship behavior from male sticklebacks.<ref name=":82"/> Tinbergen's main findings were that male sticklebacks responded in a relatively invariant way and attacked even the most crude of models with a red belly, but in contrast, courted a model with a swollen belly.<ref name=":82"/> He also found that when presented with both a real male stickleback and a crude model, if the model's stomach was more red, the stickleback would attack the model as opposed to the other real male stickleback.<ref name=":82"/>
