VMBO Year 3 · Behaviour · Section 8.2

Causes of behaviour

Stimuli and responses

A stimulus is a detectable change inside or outside an organism. A reaction to it is called a response. Many forms of behaviour involve responses to stimuli.

• External stimuli come from the surroundings, such as light, sounds or smells.
• Internal stimuli arise within the body, such as changes associated with hunger, thirst or fear.

These influences often work together. Seeing food is an external stimulus; signals associated with hunger increase the likelihood of eating.

Motivation

Motivation describes an organism's readiness or tendency to perform particular behaviour. The same external stimulus may produce different behaviour depending on internal state. An animal that has just eaten may show less interest in food than a hungry one. Motivation is useful for explaining many behaviours, but not every reflex or automatic response requires a conscious desire to act.

Sign stimuli

A sign stimulus is a particular feature or signal capable of triggering a characteristic response under suitable conditions. Its effect depends on the animal's internal state and context. The open beak of a begging chick, for example, can stimulate feeding by its parent.

Such stimuli are recognisable features associated with a particular response. They do not guarantee the response in every possible situation.

Supernormal stimuli

A supernormal stimulus is an exaggerated version of a natural stimulus which can elicit a stronger response. In some experiments, a bird may prefer a model egg larger or more conspicuous than its own eggs. Exaggerating relevant features makes the model especially effective, within limits.

Stimuli and human behaviour

Advertising uses visual, auditory and other cues to influence consumer behaviour. Bright packaging, emotionally engaging music and attractive images of food may draw attention or increase interest. Their effects depend on experience, needs and circumstances; people do not all respond in the same way.

Putting the influences together

Behaviour is influenced by the interaction of external information, internal state, inherited tendencies and experience. Stimuli and motivation provide a useful model for understanding why the same animal may respond differently at different times.