Cognitive dissonance is the mental tension you feel when two of your beliefs, or a belief and an action, contradict each other. You value your health and you smoke; you think of yourself as honest and you have just told a lie. Leon Festinger, who set out the theory in 1957, argued that the tension is unpleasant enough that people work to reduce it, and that they often do so not by changing what they do but by changing what they believe.

Cognitive dissonance at a glance

  • What it is: discomfort caused by holding inconsistent thoughts, or by acting against your own views.
  • Who described it: the American social psychologist Leon Festinger, in A Theory of Cognitive Dissonance (1957).
  • Three ways out: change the behaviour, change the belief, or add a justification that makes the conflict feel smaller (“one cigarette won’t hurt”).
  • What it is not: a diagnosis, a disorder or a sign of low intelligence. It is an ordinary response that almost everyone has.
  • Close relatives: confirmation bias and the wider family of cognitive biases.

The $1 vs $20 experiment

The study that made the theory famous was published by Festinger and James Carlsmith in 1959. Seventy-one male students at Stanford University spent an hour on two deliberately tedious tasks: putting 12 spools on a tray, emptying it and filling it again for half an hour, then turning 48 square pegs a quarter turn at a time for another half hour. Afterwards most were asked to tell the next participant, who was in fact working with the experimenter, that the tasks had been interesting and enjoyable. Some were paid $1 for this, others $20; a control group was not asked to say anything.

Later, in what looked like an unrelated interview, everyone rated how enjoyable the tasks had been on a scale from −5 to +5. Data from 11 students had to be discarded, five of them because they suspected the real purpose and three because they refused the money. The averages for the rest:

  • Control (no lie): −0.45, slightly on the boring side.
  • Paid $20 to lie: −0.05, not reliably different from the control group.
  • Paid $1 to lie: +1.35, clearly positive.

The surprise is the direction. A larger reward produced less change of opinion. Twenty dollars, a large sum in 1959, was a perfectly good reason to say something untrue. One dollar was not, so the students who took it were left with a contradiction: “I said it was fun” and “it was dull”. The easiest belief to adjust was the second one.

Other classic studies

After a choice: spreading the alternatives

In 1956 Jack Brehm asked people to rate household products, then let them choose between two they had rated similarly. When they rated the items again, the chosen one tended to look better and the rejected one worse. This “free-choice” effect is why a decision, once made, often feels more obviously right than it did while you were making it. Knox and Inkster found a real-world version in 1968: bettors at a racetrack were more confident about their horse just after placing their bet than just before.

Suffering for a group

In 1959 Elliot Aronson and Judson Mills had students pass a mild or a severe “initiation” before joining a discussion group, then listen to a deliberately dull discussion. Those who went through the severe version rated the group more favourably. Having paid a price, people are motivated to believe it was worth it.

When a prophecy fails

Festinger’s idea grew partly out of fieldwork. In When Prophecy Fails (1956), he and his colleagues Henry Riecken and Stanley Schachter described a small group that expected the world to end on a set date. When it did not, some members did not abandon the belief but explained the failure and became more eager to spread their message. It is a case study rather than an experiment, but it shows the theory’s central claim: when evidence and commitment collide, commitment often wins.

Hypocrisy as a lever for change

Dissonance can also push behaviour in a better direction. In a 1994 study, Jeff Stone, Elliot Aronson and colleagues had young adults publicly argue that safe sex matters, then reminded some of them of times they had not used condoms themselves. Faced with the gap between what they preached and what they did, more of them bought condoms at the end of the session, and they bought more on average, than participants in the control conditions. Being made aware of your own inconsistency can motivate you to close it in the direction you already endorse.

Where it comes from: children and monkeys

Is dissonance a product of adult self-image? Louisa Egan, Laurie Santos and Paul Bloom tested this in 2007 with preschool children, choosing between stickers, and with capuchin monkeys, choosing between coloured sweets. After choosing between two equally liked options, both groups later preferred a new option over the one they had rejected, which they did not do in a control condition with no first choice. The authors read this as the first evidence of decision rationalisation in young children and non-human primates.

Avoiding information: dissonance and confirmation bias

Festinger predicted that people would avoid information likely to increase dissonance. A 2009 meta-analysis by William Hart and colleagues found a moderate preference for information that supports existing views (d = 0.36). The preference was weaker when the person’s view was not tied to their values or held with conviction, and when they felt confident; it reversed when challenging information was useful for a goal they were pursuing. This is where dissonance meets confirmation bias: one way to keep the tension low is simply not to look.

Does a high IQ protect you?

There is no evidence that it does, and some evidence that reasoning skill can be recruited to defend a position. In a 2017 experiment, Dan Kahan and colleagues gave people a tricky data-interpretation problem. Those highest in numeracy did best when the data were about a new skin-rash treatment. When the same numbers were about a gun control ban, answers became politically polarised, and the polarisation was greater, not smaller, among the most numerate. The authors call this identity-protective cognition rather than dissonance, but it makes the same practical point: being good with numbers did not stop people reaching the conclusion that fitted their views.

Reasoning ability and the willingness to apply it even-handedly are different things. Our pages on critical thinking and the availability heuristic look at other ways capable people misjudge.

Has the theory held up?

The idea is one of the most cited in social psychology, but some of its classic methods have been questioned.

  • The free-choice paradigm. In 2010 Keith Chen and Jane Risen argued that the classic “spreading” of alternatives can appear even when preferences do not change at all, as a statistical by-product of the rate–choose–rate design. Later studies that controlled for this, such as one in Geneva in 2014, found that choice did change preferences for some materials (the rejected odours) but not others (faces).
  • The induced-compliance paradigm. In 2024 a team led by David Vaidis in Toulouse ran the same essay-writing procedure in 39 labs in 19 countries, with 4,898 participants. Writing an essay against one’s own view did shift attitudes compared with writing a neutral essay, but there was no difference between high and low choice, the comparison the theory depends on. The authors concluded that the paradigm may not provide robust evidence for dissonance.

The fair summary: people clearly justify their choices and commitments, and inconsistency clearly feels uncomfortable, but the size of the effect in the best-known laboratory set-ups is smaller and less reliable than textbooks once suggested.

How to deal with cognitive dissonance

  • Name the conflict. Write down the two thoughts that clash. Vague unease is easier to explain away than a clear contradiction.
  • Notice the quick justification. “Everyone does it” and “it was worth it anyway” are often signs that the belief is being bent to fit the behaviour.
  • Look for the uncomfortable evidence on purpose. The meta-analysis above suggests the default is to avoid it.
  • Separate the decision from your identity. A mistaken purchase or opinion is easier to revise when it is not a verdict on who you are.
  • Use the tension. As the hypocrisy studies show, the same discomfort can be a reason to bring your actions into line with what you believe.

Trust and scope notes

This page summarises published research for general information, with figures taken from the studies listed below. Cognitive dissonance is a concept from social psychology, not a clinical diagnosis. If inner conflict is causing you persistent distress, a qualified professional is the right person to talk to. The IQ Revealed test is an online reasoning test of 40 original items for adults aged 18 and over; it does not measure cognitive dissonance, and a reasoning score says little about how someone handles conflicting beliefs. Our guide to how IQ tests work explains what an online test can and cannot tell you.

IQ Revealed is not affiliated with, endorsed by or connected to the researchers, universities, journals or publishers named on this page. Names are used only to identify the research being described.