Innate Releasing Mechanisms

Innate Releasing Mechanisms Definition

Innate releasing mechanisms (IRMs) are a neural network in the brain that responds to a specific stimulus and triggers a particular response. The response is a fixed action pattern (FAP), a sequence of actions that cannot be interrupted and must be completed even if the stimulus is no longer present.

The Difference Between Fixed Action Patterns and Innate Releasing Mechanisms

IRMs and subsequent FAPs are an outlet for pent-up aggression, according to Konrad Lorenz, later expanded upon by Nick Tinbergen.

An IRM indicates a direct link between a scenario or situation and behavioural responses. Think of the IRM as the thing that needs to be activated to trigger a FAP. It takes a specific stimulus to activate the IRM, which triggers the FAP.

Fig. 1 - Dogs display aggressive behaviours, but are they innate?

As we mentioned earlier, an innate releasing mechanism is the existing neural network in the brain that is hardwired to the species. It is what recognises the stimulus that occurs to trigger a pattern of behaviour in response. The behaviour pattern triggered is called a fixed action pattern. Fixed action patterns arise because of the innate triggering mechanism that initiates them.

Innate Releasing Mechanisms in Ethology

Konrad Lorenz was the first to coin the term fixed action patterns, and his research has been extended several times, most notably by Niko Tinbergen, who coined the term innate releasing mechanisms.

Both suggested that release could also be interpreted as the lifting of inhibitions.

The aggression is stored, and then certain stimuli remove the inhibitions to release it, which can be seen in the hydraulic model of instinctive behaviour. This is not always the case, because not all innate releasing mechanisms involve aggression. As mentioned earlier, behaviours are innate and instinctive.

Greylag Goose Egg-retrieval

In this study, Lorenz and Tinbergen examined the behaviour of geese when an egg was displaced from the nest. They found that after the goose leaves the nest, it performs a series of movements to bring the egg back:

1. The goose notices the egg first, and this is the signal stimulus.
2. Then the goose stretches her neck over the egg so that the egg comes under her beak.
3. With the underside of its beak, the goose rolls the egg back into its nest.

An important note about this process is that if you moved the egg while the goose was rolling it back into its nest, the goose would continue the process until the end. It did not matter that the egg was no longer there, and here we can confidently say that it was a fixed pattern of action. The behaviour had to be completed even if the egg was moved.

Fig, 2 - Egg retrieval behaviour can be found in greylag geese¹.

The sight of the egg outside the nest is the specific stimulus required to trigger this sequence of behaviours, and scientists were able to manipulate this further by testing what about the egg did this.

They found that the goose responded to an object that resembled an egg in shape, size and weight in the same way it responded to an egg. This led to the term ‘sign stimulus’, also known as the release, because when the object was similar to the egg and taken away, the goose exhibited the FAP behaviour in response.

What do we mean by the Word ‘Innate’? How Does This Work in Humans?

It is something that has been controversial in the course of research on this topic. After studying birds and fish to understand fixed patterns of action and innate triggering mechanisms, transferring this research to other animals, especially humans, has caused some problems.

Most importantly, it has been difficult to determine whether a behaviour is innate or learned. To say that a behaviour is innate, it must be observed in animals that have not yet had the opportunity to learn it, usually young animals.

Fig. 3 - Can we truly say behaviours are innate or learned?

In humans, however, it is much more difficult to establish an IRM and subsequent FAP because culture and social norms govern the behaviour of many people. Where a social situation triggers a smile in one group of people, it triggers nothing at all in another. Some even feel it is impolite to smile in certain situations.

Examples of the Innate Releasing Mechanism

Here is an example of an IRM concerning male sticklebacks.

Problems with Innate Releasing Mechanisms

There are some problems with the theory of innate releasing mechanisms and the following fixed action patterns that occur.

• Reductionist: innate releasing mechanisms reduce complex behaviours to a simple, biological factor.

• Measuring intention: it is difficult to measure intention in animals and humans accurately. We cannot say with certainty that IRM and FAP are due to an animal’s aggressive nature because they cannot tell us their intention.

• Not applicable to humans: the research conducted on animals is not generalisable to human behaviour, and so far, studies have found it difficult to establish exames of IRMs and FAPs in humans.

Humans have a complex system that determines their behaviour, namely free will. While certainly innate in some species, aggression is not so uncontrolled in humans. We have a choice to act out our anger, and most situations and stimuli do not result in instinctive behaviour in humans that must be carried out.