Habituation - Examples of The Habituation Process in Animals and Humans

Examples of The Habituation Process in Animals and Humans

Habituation has been observed in an enormously wide range of species from motile single-celled organisms such as the amoeba and Stentor coeruleus to sea slugs to humans. Habituation processes are adaptive allowing animals to adjust their innate behaviors to changes in their natural world. A natural animal instinct, for example, is to protect themselves and their territory from any danger and potential predators. It is obvious that an animal needs to respond quickly to the sudden appearance of a predator. What may be less obvious is the importance of defensive responses to the sudden appearance of any new, unfamiliar stimulus, whether it is dangerous or not. An initial defensive response to a new stimulus is important because if an animal fails to respond to something that could potentially be dangerous, it could turn out deadly. Despite this initial innate defensive response to an unfamiliar stimulus, the response becomes habituated if the stimulus repeatedly occurs but causes no harm. An example of this is the prairie dog habituating to humans. Prairie dogs give alarm calls when they detect a potentially dangerous stimulus. This defensive call occurs when any mammal, snake, or large bird approaches them. However, they habituate to noises, such as human footsteps, that occur repeatedly but result in no harm to them. If prairie dogs never habituate to nonthreatening stimuli, they would be constantly sending out alarm calls and wasting their time and energy. However, the habituation process in prairie dogs may depend on several factors including the particular defensive response. In one study that measured several different responses to the repeated presence of humans, the alarm calls of prairie dogs showed habituation whereas the behavior of escaping into their burrows showed sensitization.

Another example of the importance of habituation in the animal world is provided by a study with harbor seals. In one study researchers measured the responses of harbor seals to underwater calls of different types of killer whales. The seals showed a strong response when they heard the calls of mammal-eating killer whales. However, they did not respond strongly when hearing familiar calls of the local fish-eating population. The seals, therefore, are capable of habituating to the calls of harmless predators, in this case harmless killer whales. While some researchers prefer to simply describe the adaptive value of observable habituated behavior others find it useful to infer psychological processes from the observed behavior change. For example habituation of aggressive responses in male bullfrogs has been explained as “an attentional or learning process that allows animals to form enduring mental representations of the physical properties of a repeated stimulus and to shift their focus of attention away from sources of irrelevant or unimportant stimulation.” Even odor habituation can take place centrally, in the brain. In rats Deshmukh and Bhalla (2003) hypothesized that cells in the hippocampus could time the intervals between odor inputs; frequent stimuli resulted, in their study, in a cessation of response at the level of the hippocampus.

Habituation of innate defensive behaviors is also adaptive in humans, such as habituation of a startle response to a sudden loud noise. But habituation is much more ubiquitous even in humans. An example of habituation that is an essential element of everyone’s life is the changing response to food as it is repeatedly experienced during a meal. When people eat the same food during a meal, they begin to respond less to the food as they become habituated to the motivating properties of the food and decrease their consumption. Eating less during a meal is usually interpreted as reaching satiety or “getting full”, but experiments suggest that habituation also plays an important role. Many experiments with animals and humans have shown that providing variety in a meal increases the amount that is consumed in a meal, most likely because habituation is stimulus specific and because variety may introduce dishabituation effects. Food variety also slows the rate of habituation in children and may be an important contributing factor to the recent increases in obesity.