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Problem :

A female Herring gull has a red spot on her beak. When they see this spot, her chicks will peck at it and the female bird will regurgitate food for the chicks. Identify two key stimuli and their resulting fixed action patterns in this situation.

The red spot on the female bird's beak acts as a KS to the chicks causing the beak pecking FAP as a result. The pecking in turn acts as a KS for the female bird, triggering the regurgitation FAP.

Problem :

A male stickleback fish will normally become aggressive upon seeing the red belly of another male stickleback. These males will become extremely aggressive when they see a large red object. Why does this happen?

The aggression FAP is released by the color red (the KS). A red object that is much larger than a normal stickleback belly will act as a supernormal stimulus and thus release a reaction that is stronger than normal.

Problem :

Ducklings must crouch to avoid predators that fly overhead. The silhouette of predatory birds is the same shape as that of adult ducks in reverse. A duckling knows to crouch when a predatory bird flies overhead, but does not crouch when adult ducks do. What two key stimuli does the duck require to trigger the crouching fixed action pattern?

The shape of the bird overhead is one KS, but it is not sufficient to trigger the crouching FAP. The shape must also be moving in the correct direction to be identified as a predator and trigger crouching.

Problem :

In the above problem, what type of stimulus is the combination of predator shape and direction that triggers the crouching FAP in ducklings?

A stimulus which consists of two distinct KS units that are both required to trigger the FAP is known as a configurational key stimulus.

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