Releaser, terminator and sign stimuli

The stimuli which cause the actual behaviour pattern to be initiated are referred to as releaser stimuli or just as releasers. An example is the red patches at the base of the beak of the herring gull. This is the releaser for the pecking behaviour of the chicks when the adult bird appears. The pecking action is the releaser causing the parent bird to regurgitate food material from its stomach. This type of released behaviour between individuals regulates much of their social interaction.

Once a behavioural pattern has been carried out it is often necessary to stop it. A termination stimulus (or suppressor) frequently achieves this. A fully stretched stomach causes termination of eating behaviour. An interesting and recently discovered point, concerns the reason why you feel hungry soon after a really big Chinese meal. This is because the low level of fat in the food does not sufficiently stimulate a group of fat detectors in the brain. This information is fed to the cortex, which activates the hunger circuitry much sooner than you would expect.