Psychological Sets

The Basic Idea

Imagine you’re walking on the sidewalk with a friend and you see a pile of stones—two side by side, and then a chain beneath them forming a curved line. It reminds you of a smile. “Look,” you say. “A face.”

Days later, you’re making pancakes for your toddler, and you pull out some blueberries to put on top. The shape of the pancake reminds you of something: you put two blueberries side by side forming eyes, and then a row beneath them to form a happy face. “Look,” says your two-year-old. “A face.”

Of course, it is difficult not to see a face in these instances—because you see faces frequently, your mind is accustomed to them, and therefore begins to perceive them in other contexts. In this case, you are making use of a psychological set: a group of expectations that guides our perceptions and behaviors. Because your mind is used to things being a certain way, the psychological set colors your expectations, and helps you perceive the world in ways consistent with your views. While the face perception example describes a “perceptual set,” psychological sets are called “mental sets” when they inform how we solve problems.

We don’t see things as they are—we see things as we are.

– Anaïs Nin, writer

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Key Terms

Mental sets: Psychological sets that rely on familiar ways of solving problems.

Perceptual sets: Psychological sets that rely on familiar ways of perceiving stimuli.

Schema: A cognitive framework, based on previous knowledge and experiences, that helps humans organize and interpret incoming information.


Mental sets

The mental set was demonstrated in a 1940 experiment by Abraham Luchins. In this experiment, Luchins asked subjects to fill a jug with a specified amount of water, using the content of three other jugs. Only one technique could possibly be used to complete the task. Most candidates were successful—however, this was only the beginning.

After this simple task, Luchins gave his participants a different problem, one that could be solved using the same technique, or a simpler one. Luchins believed that expectations would guide outcomes, informing his theory of psychological sets. Because of this understanding, Luchins hypothesized that his participants would use the same technique as before, even though there were simpler ones available. Luchins was correct. His experiments showed that even when alternatives are available, people tend to use processes that have proved successful in the past. In other words, they tend to rely on mental sets.

In his 1931 experiment, Norman Maier proved what is today known as a specific type of mental set called functional fixedness. Maier asked participants to find a way to attach two strings hung from a ceiling, with the use of a variety of heavy household items. Although it was possible to complete the task in all circumstances, most of Maier’s subjects could not do it because they could not see uses for these objects other than the ones for which they were designed. For example, they could not possibly see a way a vacuum could be used to tie together two strings, since they were held back by their understanding of what a vacuum is actually used for. Since people were generally unable to look outside the boxes set by their previous expectations, Maier’s subjects failed to complete the task.

Perceptual sets

In 1955, psychologists Jerome Bruner and Leigh Minturn took the idea of mental sets to inform their study of perceptual sets. They designed an ambiguous handwritten figure that could be interpreted as either the letter B or the number 13. Presenting it alongside a series of numbers, they found that the figure was frequently interpreted as the number 13. When they presented the figure alongside a series of letters, however, their predictions were proved accurate when experiment subjects saw the figure as the letter B. Bruner and Minturn realized that what you see depends on what you look for, and that expectations could frequently influence actual perceptions.


Abraham Luchins

Abraham Luchins was a student of Max Wertheimer, the originator of Gestalt psychology, a field of psychology which studies perceptions from a structuralist point of view. Although well-versed in the study of perceptions, Luchins is most well known for his research on the mental set and his water jug experiments. Luchins also contributed to a school of research on group psychotherapy and research methods.

Norman Maier

Norman Maier was an American psychologist who conducted thoughtful and creative experiments in order to provide insight on unique aspects of human behavior. He was the inventor of the “two-cords problem,” which has been widely replicated as evidence of functional fixedness. Maier is also the author of Principles of Animal Psychology, a 1935 textbook describing his extensive research on the cognitive development of rats.

Jerome Bruner

Jerome Bruner was an American psychologist well known for his contributions to cognitive learning theory and educational psychology. Having taught at Harvard, Oxford, and NYU, Bruner is one of the most cited psychologists of our time, and has made provocative research discoveries regarding how we learn, perceive, and interpret information.


Mental sets

Often, mental sets are helpful as they are based on prior experiences, and therefore can inform realistic expectations of the world around us. If there is a solution to a particular problem that has consistently worked in the past, then pulling out this solution is likely to be a quick fix, and should not be advised against.

However, when the problem changes, or a new possible solution presents itself, mental sets can hold us back as we try to work within what we know and resist the temptation to try new things. While having relevant experience is often seen as an advantage in the workplace, it is not always a driver of creativity—and bringing in a novice can often provide a fresh perspective on a problem.

One mental set in particular is referred to as functional fixedness: the inability to use objects in ways they were not designed for. When you have plenty of experience with an object, you may be unable to make uses for it outside the use for which it was intended. When you encounter a new object, however, you may be able to see how it could do other things to solve a problem because your expectations have yet to be clouded by your experiences.

“The definition of insanity is doing the same thing over and over again and expecting different results.”

—Albert Einstein

Perceptual sets

Similarly to mental sets, perceptual sets can be both adaptive and inhibiting. While they lead us to make accurate conclusions about our world based on prior expectations, perceptual sets can also keep us within a box prescribed by our own conscious, and close us off to a world that does not fit within our expectations.

Many people have had the experience of going through a breakup, and suddenly seeing signs of their ex-lover everywhere they look. In another context, you may learn a new word and start seeing it everywhere. While the actual world around you hasn’t changed, your perception has. It’s the same reason practising gratitude or harboring an optimistic outlook can cause more positive things to show up in your life—what’s there has not changed; what you’re looking for has.

“What we see deeply depends on what we look for.”

—John Lubbock


  1. The pitfalls of “expertise”
    In the late 1990s, psychologist Jennifer Wiley took the idea of mental sets a step further, relying on the experience of fixation: when a person clings rigidly to a mental set that is not proving effective. Wiley’s work revealed that experts, obviously well-versed in their fields, were particularly susceptible to fixation as a result of having highly ingrained mental sets about specific ways to solve a problem. Although it is widely believed that experience will provide the foundation on which problem solving can thrive, this finding—replicated by others—reminds us that a fresh perspective can bring a fresh solution, and that expertise is not always all it’s cracked up to be.
  2. The power of suggestion
    Perhaps you remember the 2018 debate about a famous and divisive audio clip circulating on Reddit. In this audio clip, listeners could often hear both the names “Yanny” or “Laurel” if they listened closely. Regular people were in uproar, shocked and confused that one sound could have two completely different takeaways. It was later revealed that in actuality, “Laurel” was the sound originally recorded—however, pitched at a high enough frequency, the brain could easily interpret this sound as “Yanny.”
    While it is possible that either sound could be heard, your interpretation of the audio clip may also depend on your expectations. If a person, prior to having you listen, told you that the sound said “Yanny,” you may be more likely to hear it that way. Just as you should not ask a child if they have a stomach ache because they may suspiciously develop one, the existence of perceptual sets everywhere—even on Reddit—reminds us of the power of suggestion.

Case Studies

Mental sets and medical diagnoses

Even esteemed professionals in our society are susceptible to mental sets. When you arrive at the doctor’s office and begin listing off your recent symptoms, your doctor is challenged with the task of paying attention to you—not the other dozen patients she saw that day. While she listens to you, however, your doctor’s mental picture of your diagnosis and prognosis is subconsciously influenced by the expectations she has around those symptoms, which have been shaped by her other patients’ experiences. Although doctors are surely doing their best, diagnoses are not 100% accurate—and a mental set may cause a doctor to overlook some aspects of your predicament while emphasizing others that suit her expectations. Of course, mistakes that stem from these mental sets can have an enormous compounded impact on patients’ lives, potential health results, and healthcare funding.

Emotional affect and creativity

In a 2013 study, researchers Haager, Kuhbandner, and Pekrun were able to prove that a positive mood could be beneficial in overcoming the constraints of a mental set. They had participants solve 60 similar problems which were all solved using the same complex strategy. They then gave the participants a break, and purposely induced either positive or negative moods in all of them. Afterward, participants continued to work on the problems, the new ones offering up a potentially simpler solution. The researchers found that participants experiencing a positive mood were much more likely to find the simple solution and use it than those experiencing the negative mood. This finding is important, as it teaches us that frustration begets frustration: when you are in a negative mood, don’t try solving a complex problem. A simpler solution might present itself from a sunnier disposition.

Related TDL Resources

Priming, explained.

Priming is what happens when you are manipulated into seeing something a certain way because of prior stimuli. It is one effect of perceptual sets, and can have an undue impact on how we make daily decisions.

The Dunning-Kruger effect, explained.

The Dunning-Kruger effect describes why our perceptions of our own talents are inhibited and manipulated by the level of our skills themselves. As we know from mental sets, expertise can sometimes be a barrier to creativity, and novices can often provide innovative ideas in the workplace.

Confirmation bias, explained.

What we see depends on what we look for. Confirmation bias describes our tendency to seek out information that corresponds with beliefs we already hold.


Abraham S. Luchins. (2008, May 8). Wikipedia, the free encyclopedia. Retrieved February 13, 2021, from

Blackburn, S. (2020, May 1). How psychology explains how expectations influence your perceptions. Verywell Mind.

Cherry, K. (2020, December 3). How do mental sets impact your ability to solve problems? Verywell Mind.

Furong, H., Shuang, T., & Zhujing, H. (2018, December 11). Unconditional perseveration of the short-term mental set in chunk decomposition. Frontiers.

Green, H. (2014, March 17). Perceiving is Believing: Crash Course Psychology #7 [Video]. YouTube.

Haager, J. S., Kuhbandner, C., & Pekrun, R. (2013). Overcoming fixed mindsets: The role of affect. Cognition and Emotion28(4), 756-767.

Jerome Bruner. (2003, July 5). Wikipedia, the free encyclopedia. Retrieved February 15, 2021, from

Problem solving. (2002, February 25). Wikipedia, the free encyclopedia. Retrieved February 13, 2021, from

McLeod, S. (2010). Perceptual set. Study Guides for Psychology Students – Simply Psychology.

Norman Maier. (2012, March 8). Wikipedia, the free encyclopedia. Retrieved February 13, 2021, from

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