What is the name of process in which the response of stimuli decreases after repetitive exposure?

When we enter a room, we may feel distracted about the noisy sound produced by an old air conditioning unit. But when we spend more time inside the room, we tend to ignore the annoying and sound although it is still present. This situation is an effect of habituation. It does not require the animal or person to be aware of this process; it may occur naturally and unconsciously.

A. Basics of Habituation

Habituation is actually a basic process of biological systems. Without it, we would not have the ability to identify the meaningful and changing information from stagnant and irrelevant ones.

Habituation is said to be present in every species of animal, including humans.There are many factors that influence the emergence of habituation in an organism. The two most important factors are:

1. The amount of time in between the first presentation of the stimulus to the organism up to the second presentation, known as inter-stimulus interval.
2. The length of time during which the stimulus is presented, known as stimulus duration.

Suppose there are two stimuli: A and B. The stimulus duration of A is 10 seconds, while that of B is 20 seconds. The concept of habituation holds that the longer the organism is exposed to the stimulus, the faster habituation occurs. Therefore, comparing the stimulus duration of A and B, we can conclude that habituation happens faster in B than in A because the organism is exposed to it. It can be said that the organism got used to B more than to A, and “habit” may be developed in the presence of B than A.

One of the most interesting facts about habituation is that the decrease in response is specific only to the stimulus with which the habit is developed. For example, if you are habituated to the taste of chocolate flavored ice cream, your degree of responding to vanilla flavored ice cream will significantly increase because you have not developed a “habit” of it yet.

B. Significance in Humans

Habituation has a scientific importance in terms of testing psychological phenomena in both animals and humans. For example, an infant may gaze upon a visual stimulus that has been presented to him for 1 minute. After habituation to that stimulus, the observer will determine the amount of time the infant spends in looking at a new stimulus. Then, the observer will compare the results and see if there is a similarity between the two stimuli presented.

Habituation simply means that a person tends to ignore the stimulus to which he has been exposed too many times. For instance, after you wear pants, you will ignore the clothing stimulus as you continue on with doing other things. This is because the pants stimulus has already disappeared perhaps due to neural adaptation in the sensory nerves. If you are habituated to wearing pants when going outside, but you suddenly wear a skirt today, your degree of response to the change in clothing stimulus is increased. This may explain the reason why you may become a bit shy or “not yourself” and often thinks if you look good on that clothing. But after several hours, you feel as though you "got used to it" and no longer puts your attention on it.

By Nathalie Boutros, Ph.D.
​Reviewed by Tchiki Davis, M.A., Ph.D.

What is habituation? Learn what habituation is, the conditions under which it may occur, and how habituation may impact your life.

You have just experienced habituation. The loud and surprising sound initially got your attention and alerted you to the possibility of danger. When it became clear that you weren’t in any danger, your brain determined that it could safely ignore the sound and focus your attention and cognitive resources on other things. In this article, we’ll define habituation and review some psychological principles of habituation. We’ll also discuss how habituation may impact your life and ways that you may be able to overcome some of the undesirable effects of habituation.​

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Habituation is the reduction of a behavioral response to a stimulus after repeated presentations of that stimulus (Rankin et al., 2009). Habituation can occur to stimuli detected by any of your senses. You may become habituated to loud sounds, bright lights, strong odors, or physical touch. Learning to ignore and filter out stimuli that are irrelevant, unimportant, or uninformative may allow you to devote more of your attention and cognitive resources to other things, including things that may signal danger.

Broadly, learning can be defined as any change in behavior that happens after a specific experience. The category of behavioral changes that qualify as learning is vast. Incredibly complex, exclusively human accomplishments like learning how to drive a car, bake a cake, perform surgery, or integrate a differential equation are all examples of learning. Learning can also cover much simpler behavioral changes. 

Habituation has been called the simplest form of learning (Schmid et al., 2015) and is present in many species. Even single-celled organisms are capable of habituation (Eisentstein et al., 1982). The simplicity of habituation, its ubiquity across species, and its relatively straightforward neural underpinnings mean that it is often studied in model species by scientists interested in the neuroscience of learning and memory (Kandel, 2012).

Almost any response or behavior may become habituated. The first time you’re exposed to something intense or surprising you may respond by jumping, calling out in surprise, exploring the environment, or simply looking around. Feelings may also become habituated. You may feel less afraid of your neighbor’s Halloween decorations as October progresses or may feel less annoyed by your new officemate’s loud chewing as time goes on. 

The following clips show some examples of habituation in people and animals. The first two show habituation of a response that occurs after a surprising and potentially danger-signaling stimulus. The last video demonstrates that habituation can also occur to something that doesn’t signal the potential for danger but that is merely interesting.

Although scientists and philosophers have been writing about the phenomenon of habituation for  centuries (Thompson, 2009), it wasn’t formally defined until 1966 (Thompson & Spencer, 1966). Psychologists who study habituation have identified ten characteristics that define habituation (Rankin et al., 2009).
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1. Repeated presentations of a stimulus decrease some dimension of the response to that stimulus. The affected dimension may be the frequency, probability, duration, or magnitude of the response. The response may never fully go away but may instead approach some minimum. The first firework of the night may cause you to jump out of your seat. As the fireworks continue, your reactions may get smaller and smaller until you don’t feel at all surprised or startled by the explosions.
2. Spontaneous recovery: the response to the stimulus will recover if the stimulus is absent for a period. If you only see one firework show a year you may find that your startle response is back to its high point for the first firework of the show each year.
3. Potentiation of habituation: Habituation of the response to the stimulus happens faster each time. If you manage to make it to more than one firework show in a single night, you may find that you habituate faster at the second, third, fourth, and subsequent shows.
4. More frequent stimulus presentation will result in faster or more pronounced habituation (and spontaneous recovery). You’ll probably habituate to the sound of the fireworks faster if they are released every second than if they are released every thirty seconds.
5. Habituation will be faster and more pronounced for weaker or less intense stimuli. Strong stimuli may never produce habitation in some cases. You may habituate to the sound of faraway fireworks within a few minutes but may never get used to the sound of fireworks being set off right next to you.
6. Repeated presentation of the stimuli even after you have become fully habituated to it may have some effects that you’ll only be able to detect in other situations. If the fireworks continue even after you’ve become fully habituated, you may find that you don’t have any startle response to the sound of a car backfiring in the parking lot on the way home from the show.
7. Stimulus specificity: Habituation to one stimulus doesn’t mean that habituation will happen to another stimulus. Although you may have habituated to the sound of fireworks, you may not show any habituation to the sound of loudly barking dogs or crying babies.
8. Dishabituation: If a second, intense, stimulus is presented, the habituated response may reappear in response to the originally habituated stimulus. If someone screams right in your ear after you’ve habituated to the fireworks, the next firework may cause you to startle again.
9. Habituation of the dishabituating stimulus: repeated presentation of the new stimulus will reduce its ability to reverse habituation. If the screamer keeps on screaming right in your ear, to the point where it doesn’t surprise you anymore, your startle response to the fireworks may continue to be habituated.
   
10. Habituation can last for a long time. Habituation of a response may be faster each successive time. If you get a job at an amusement park or other venue where you hear fireworks every night, you may find that your startle response goes away faster and faster each night.

Habituation is very similar to sensory adaptation. Both sensory adaptation and habituation describe a decrease in reactivity to a stimulus after repeated exposure to that stimulus. However, habituation is a behavioral learning effect while sensory adaptation is a physiological effect.

In sensory adaptation, the receptor cells become adapted to a particular level of stimulation (Dalton, 2000). For example, the receptor cells in your nose may adapt to a specific smell, and may no longer respond when they detect that particular aroma. This may be why people don’t tend to notice the smell of their own homes.

In contrast, habituation is a phenomenon of the cells in the nervous system. It is a form of learning, consisting of the brain trying to filter out irrelevant background stimuli in order to allow more attention to be paid to potentially relevant stimuli. For example, imagine that an avid griller moves in next door to you and sets up their grill near your bedroom window. The first time you smell the woodsmoke you may become alarmed, fearing a nearby fire. Repeated exposure to the woodsmoke, without any indication of fire danger, may habituate you to the smell of the smoke to the point that you don’t even notice when your neighbor lights up the grill. It isn’t that the receptor cells in your nose have stopped reacting to smoke - you will still likely notice and perhaps become alarmed if you smell cigarette smoke in your home. Rather, your nervous system has learned that the smell of smoke coming from your neighbor’s grill doesn’t signal danger.

Sensitization is the opposite of habituation. While habituation is a decrease in reactivity to a stimulus after repeated presentations of that stimulus, sensitization is the opposite—increased reactivity to a stimulus after repeated stimulus presentations (Cevik, 2014). Habituation may be adaptive when it allows you to filter out meaningless stimuli so that you can focus your attention on informative stimuli. Sensitization may be adaptive when it allows you to hone in on useful and informative stimuli. For example, if you hear a mosquito buzzing near your ear, you may become sensitized to the sound of buzzing. This may allow you to find and squish the mosquito before it has a chance to sting you. On the other hand, you may become habituated to the sound of buzzing when it's coming from the fluorescent light above you. Being attentive to the sound of the mosquito may help you avoid injury or discomfort. Being attentive to the sound of the fluorescent light probably won't help you in any way.

Habituation and sensitization are opposite to one another at the cellular as well as the behavioral level. At the cellular level, habituation involves the reduction of neurotransmitter release upon successive presentations of the stimulus (Glanzman, 2009). Sensitization involves an increase in neurotransmitter release upon successive presentations of the stimulus (Barbas et al., 2003). 

If you hit the lottery jackpot tomorrow, do you think you’d be happier in five years than you are now? The answer seems obvious—of course, you would be! However, research findings don’t support this conclusion—lottery winners don’t tend to be any happier than people who haven’t won the lottery (Brickman et al., 1978). This is despite reporting that they had more financial security, more leisure time, and an easier retirement after winning the lottery. Habituation may be at play here—lottery winners may have access to a whole new set of enjoyable experiences, leading to increased happiness and pleasure. However, as they are repeatedly exposed to these new happiness-producing stimuli, their happiness responses may become habituated and the new experiences may no longer increase happiness. People tend to adapt to good and bad events and return to the same baseline level of happiness. Happiness may adapt just like startle responses or exploratory behavior.

According to the Sustainable Happiness Model (Sheldon et al., 2013), happiness is composed of three components: your genetics, the largely stable psychobiological characteristics that you’re born with; your circumstances, the situational characteristics that you find yourself in; and activities, the things that you do in your day-to-day life.  According to this model, activities account for about 40% of a person’s happiness. Changing your activities may be the most straightforward way to change your happiness and prevent habituation of happiness. Research on the sustainability of happiness has found many ways to maintain increased happiness. You may be able to stay happy by intentionally practicing and expressing gratitude (Wood et al., 2010), reflecting on your life through the process of journaling (Burton & King, 2008), or by committing acts of kindness (Curry et al., 2018).

You may also be able to stave off habituation of happiness by taking part in new activities (Sheldon & Lyubomirsky, 2007). Giving yourself new, positive, enjoyable experiences and activities may keep you happier for longer.

When people get married they often experience an increase in their happiness and well-being (Waite and Lehrer 2003). Marriage may increase happiness and well-being by increasing social support, emotional support, intimacy, and companionship. Marriage isn’t necessary for these benefits. Unmarried people in committed, cohabiting relationships show similar increases in happiness and well-being at the start of their committed partnerships (Zimmerman & Easterlin, 2006).

After a “honeymoon period” of about two years, happiness levels tend to return to their pre-marriage levels (Lucas et al., 2003). The increased happiness after getting married or starting a committed relationship appears to be transient.

How can you overcome this decline in happiness and life satisfaction from its high point immediately after getting married or initiating a committed relationship? Friendship. People who report that their partner is also their best friend tend to show sustained increases in happiness and life satisfaction after marriage (Grover and Helliwell, 2019). Marriage and committed relationships come with many benefits. However, the social benefits of relationships may be the most important. Having a partner who is a companion, who supports you, and who you simply like to be around, may allow you to continue to live in a “honeymoon” state even after the initial “honeymoon period” of the first few years of a marriage or committed relationship.

Here are some books that may help you learn even more.

Habituation is an adaptive process—it allows you to filter out irrelevant or uninformative stimuli so that you can focus on information that is relevant and important. As you experience the same thing without any changes, you stop noticing it. This is very helpful when it comes to getting a good night’s sleep in a noisy city apartment or learning to ignore the garden hose that looks like a snake. However, when habituation happens to experiences that bring you joy, it may become a problem. Avoiding habituation once you have achieved a goal or have settled into a relationship may require that you intentionally take the time to introduce novelty into your life. You may want to make sure that you continue to give your brain and your senses new stimulation to avoid habituating to the sources of your happiness.

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• Brickman, P., Coates, D., & Janoff-Bulman, R. (1978). Lottery winners and accident victims: Is happiness relative?. Journal of personality and social psychology, 36(8), 917.
• Burton, C. M., & King, L. A. (2008). Effects of (very) brief writing on health: The two‐minute miracle. British Journal of Health Psychology, 13(1), 9-14.
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• Curry, O. S., Rowland, L. A., Van Lissa, C. J., Zlotowitz, S., McAlaney, J., & Whitehouse, H. (2018). Happy to help? A systematic review and meta-analysis of the effects of performing acts of kindness on the well-being of the actor. Journal of Experimental Social Psychology, 76, 320-329.
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• Zimmermann, A. C., & Easterlin, R. A. (2006). Happily ever after? Cohabitation, marriage, divorce, and happiness in Germany. Population and development review, 511-528.​