What Is Reactivity? Psychology Explains This Phenomenon

By: Julia Thomas

Updated March 15, 2020

Medically Reviewed By: Whitney White, MS. CMHC, NCC., LPC

Have you ever caught yourself acting differently when others can see you? Or, maybe you've noticed others behaving differently when they think no one is observing them. If so, what you might have seen were instances of a phenomenon psychologists call reactivity. Here's a look at what reactivity is, different types of reactivity, its impact, and what you can do about it.

Reactivity - Psychology Definition

Reactivity is a psychological phenomenon that happens when someone changes the way they behave because they know they're being observed. Their behavior might become more positive or negative, depending on the situation and the people involved. The person being observed may change their behavior based on their understanding of what the observer expects.

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Types Of Reactivity

Beyond the basic definition, scientists have identified several distinct types of reactivity. The following are some special types of reactivity.

Hawthorne Effect

The Hawthorne effect happens during research studies when the people participating know they're being studied. The experimenters pay close attention to them, and they change the way they behave as a result. This effect was named for the Hawthorne Works Plant, where researchers conducted a study on productivity. When an experimenter singled someone out and gave them attention, they worked harder and performed better.

John Henry Effect

The John Henry effect is a special case of the Hawthorne effect. It also happens in research studies, but in this situation, the participants affected to change their behavior because they know they're in the control group and could compare their behavior to what those in the experimental group were doing and how they were reacting. Scientists see this as an attempt to overcome what the control group participants see as a disadvantage - that nothing interesting will happen in their group, and they will not receive special attention.

Experimenter Effect

In a scientific experiment, the researchers must be extremely careful not to let the participants know what they expect the study to show. If they do, the experimenter effect can happen. This is when the participants alter their behavior based on what they think the experimenter thinks they will do.

Observer-Expectancy Effect

The observer-expectancy effect is a type of reactivity that happens when someone gives subtle cues as to what they expect that influence the performance of the person asked to do something. They may not even realize that they are giving these cues, but the person performing will pick them up, anyway.

The background behind the observer-expectancy effect is interesting. The idea is based on an experiment called the "Clever Hans" experiment. A philosopher and a psychologist wanted to find out if a certain horse could do arithmetic as its owner claimed it could. The owner would give a question, and the horse would tap out the answers with its hoof.

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The researchers noticed several things during their observations. First, if the owner didn't know the answer, the horse got the answer wrong most of the time. Second, if the horse couldn't see the owner, it couldn't get the answer right, either. Finally, they noticed that if the owner did know the answer, as the horse's taps approached the correct number, the owner's posture and facial expression changed. The horse, then, was responding to what the owner expected of them.

Pygmalion Effect And Golem Effect

Reactivity can happen in a school setting, too. In the Pygmalion effect, students change their behavior based on what they think the teachers expect from them. If a teacher expects the children to perform well, they will perform better than they would if the teacher had no expectations.

The Golem effect is similar to the Pygmalion effect, except that it happens when teachers have low expectations of their students. When they do, the students tend to slack off more and show worse performance.

A similar thing can happen to teachers as well. If a student is more attentive to the teacher's lecture, the teacher tends to grade them higher even if their work isn't better than that of the students who didn't pay attention to.

Both the Pygmalion and Golem effects can happen in other settings, too. In industrial settings, for example, the leader's expectations can change the way they treat the employees. They give employees who they expect to do better more time, attention, learning opportunities, trust, respect, and responsibilities. And this makes it much easier for those favored employees to perform better.

Bradley Effect

The Bradley effect is named after Los Angeles Mayor Tom Bradley, an African-American candidate in the 1982 race for governor of California. Bradley was far ahead in the polls but failed to win. Experts have theorized that the reason for the discrepancy between the poll numbers and the election results were related to the voters' desire to give a socially acceptable answer.

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Even though they wanted to vote for a white candidate, they didn't want to appear as a racist, so they answered the poll is saying they would vote for the African-American. But, when they were not being observed, in the privacy of the voting booth, they made a choice they wanted to make. Analysts have suggested that the Bradley effect has happened in many other elections and is still a concern today.

The Watching-Eye Effect

The watching-eye effect is a type of reactivity in which people behave differently when they're being watched. What's fascinating is that people may change their behavior even when they merely see images of eyes, such as a picture of an eye posted on a wall. This effect can be useful for crime reduction because it gives people the sense that they're being watched even if no one is present. They know that those aren't real eyes, but they respond to them as if they were.

Why Does Reactivity Matter?

Reactivity is an interesting phenomenon, but it also has a great impact in many situations. Scientists, teachers, and leaders all need to be aware that reactivity can happen and take steps to overcome it. At the same time, law enforcement departments and others can make use of this effect to bring about positive results.

In Scientific Research

In scientific studies, the researchers must design their experiments carefully to avoid unwanted reactivity. One option is to study people unobtrusively. To do that, they obtain information without the subjects, even knowing that they are a part of a research study. For example, scientists might put up a poster in a public place and watch how people passing by react to it. To avoid reactivity, they would have to stay hidden or get their data from a hidden surveillance camera. And, they would have to keep their study a secret until it was completed.

In research where unobtrusive observation is not possible, scientists most often use a blind experiment design. In a blind experiment, information is withheld from subjects, technicians, data analysts, and those experimenting. This reduces the possibility of any kind of bias that might lead to reactivity. Often, the participants don't even know what hypothesis is being tested.

In a single-blind medical experiment, the subjects wouldn't know what treatment they were being given. For example, they wouldn't know whether they were getting a placebo or an actual medication.

In a double-blind experiment, the researchers and subjects are both unaware of who is in the control group and who is in the experimental group. So, for example, when testing a medication, neither researchers nor subjects would know who was getting the placebo and who was getting the real medication.

In a triple-blind study, those monitoring the research are also unaware of who's in the control group. However, triple-blind studies are less common, because, in many instances, the people monitoring the research need to be fully informed to ensure the ethical treatment and safety of each participant.


In education, it's important for teachers to understand that the way they respond to their students may be influenced by reactivity. They need to avoid basing their evaluations of students on factors other than their actual performance. If they recognize that their expectations of students can change the students' performance, they can choose to expect the most positive results whenever possible simply.


In workplaces, leaders can use their understanding of reactivity to enhance the performance of workers. If they expect them to do well, give them attention, offer them learning opportunities, respect them, and lean towards trusting them more, the workers are more likely to perform better.

What You Can Do If You're Experiencing Reactivity

Reactivity can be a fun topic to explore. Yet, if you're in a situation where you or someone else is responding with reactivity, the consequences might be quite negative. For example, if you are a college student and your professor expects the worst of you, you may have trouble making the grade you desire. If you're a worker and your boss doesn't give you the opportunities you want, it may be because of their reactivity. As a parent, you may be puzzled at your child's bad behavior, not realizing that you're treating one of your children differently based on your expectations.

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It's always a good idea to understand what's happening so that you can deal with it appropriately and effectively. Talking to a counselor is a good option for people who are experiencing reactivity, whether through their own biases or the biases of those around them.

During your therapy, you can identify instances of reactivity that are happening in your life. Then, you can consider different ways to approach those interactions. You can talk to a counselor at BetterHelp to learn more about how reactivity is impacting you and those around you so that you and those you care about can avoid the problems that come with this phenomenon.

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