Similarity Hypothesis

The Basic Idea

Consider the closest friends you meet while backpacking abroad. You likely share many similarities; perhaps a thrill for spontaneity, hobbies, appreciation for culture, music preferences, or food choices. During the trip, you find yourself effortlessly interacting with other backpackers: sharing a relatively-unknown scenic route, a local exhibition to visit, or the best bed and breakfast in town. We often relate and empathize easily with similar individuals – this is a result of the similarity hypothesis.

The similarity hypothesis suggests that we tend to be drawn towards those who are similar to ourselves. Similarities can refer to shared attitudes and values, as well as political opinions, cultural background, or even minute details like posture.1

The experience of interacting with similar individuals jumpstarts cognitive processing, like learning, memory, attention, and reasoning. An aspiring musician might remember all the lyrics to their favorite band’s albums. An employee might pick up skills more quickly when assisted by a mentor they admire or identify with. Even when it comes to making comparisons with others, we tend to look for individuals who share similar attitudes and beliefs because it can be difficult to make accurate comparisons when others are too different from us.2

Why do we tend to be drawn towards individuals who share similar attitudes and values?

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Key Terms

Similarity Hypothesis: A hypothesis which states that we tend to be attracted towards individuals who share similar important traits, such as attitudes and values.

Cognitive Processing: A general term to describe any mental function involved in acquiring, storing, interpreting and manipulating information. These functions can be conscious or unconscious, such as attention, memory storage, learning, and reasoning.

Empathy: Understanding an individual from their point of view and experiencing that individual’s feelings, thoughts and perceptions.


In 1954, Leon Festinger proposed in his social comparison theory: when individuals are uncertain of their abilities and opinions, they tend to make comparisons with other similar individuals to assess the accuracy of their own opinion. Festinger’s influential social comparison theory introduced the similarity hypothesis. Since its introduction in A Theory of Social Comparison Processes, a large amount of evidence has supported the hypothesis.3

Festinger’s hypothesis has been used to explain phenomena in a diverse array of fields, from political science to marketing. For instance, in the 1971 The Attraction Paradigm, psychologist Donn Byrne introduced the similarity-attraction theory. Byrne’s theory was based on the similarity hypothesis. He suggested that individuals who share similar “important attitudes” (opinions on family and values) are generally more likely to be attracted to each other, compared to individuals who share similar “less important” attitudes (opinions on a specific type of sink).4 This holds for friendships as well as romantic partners. Byrne further outlined that individuals associate with those who have similar personality characteristics, such as self-esteem, optimism, and conscientiousness.

According to Byrne, personality similarity has a key role to play in the longevity and happiness of a marriage.5 Byrne’s similarity-attraction theory stated that individuals are generally romantically attracted to others who share similar physical characteristics and levels of physical attractiveness. Byrne’s work on similarity-attraction was so influential that further research has supported his theory, with individuals’ preference for similarity being demonstrated in various other aspects such as social habits and socioeconomic status.5

The similarity hypothesis then made its way into the field of economics and decision-making in Amos Tversky’s 1972 book, Elimination by Aspects: A Theory of Choice.6 Tversky influenced choice theory in economics by applying the similarity hypothesis to decision-making, changing the way modern economists approached the field. Based on the hypothesis, he suggested that when a new product enters a market, it will take more demand from the share of a similar product than a dissimilar one. This has important implications for brands: when creating a new line of products, they should make it as dissimilar as possible from their current offering to prevent market cannibalization. Tversky’s work influenced marketing managers, who started adopting his use of the similarity hypothesis to help make marketing entry decisions.7


Leon Festinger

An influential American social psychologist, most renowned for his work on social comparison theory in his 1954 book, A Theory of Social Comparison Processes. Festinger introduced the similarity hypothesis in this book, which has been followed by an enormous amount of data which has provided evidence to support the hypothesis. Several of Festinger’s theories and research also renounced previously dominant behaviorist views of social psychology.

Donn Byrne

An American psychologist and  influential contributor of foundational theory in interpersonal attraction. His work on similarity-attraction theory, based on the similarity hypothesis, was groundbreaking for exploring the relationship between similar attitudes and attraction. Byrne was also an early contributor on the psychology of human sexuality.8

Amos Tversky

One of the founders of behavioral science who helped revolutionize the field of economics and decision-making. Tversky was an influential psychologist who applied the similarity hypothesis to decision-making and choice theory in economics. Along with Daniel Kahneman, Tversky was also a pioneer in loss aversion and prospect theory.


When it comes to attraction, Byrne’s similarity-attraction theory remains relevant today as it provides reassurance that an individual is not alone in their belief. Being attracted to individuals with similar attitudes also enables one to more accurately predict the other’s behaviors in different scenarios, providing an insight into the other’s predilections and “pet peeves” based on similarity.5

Similarly, when we empathize with a target, such as a novel, our enhanced cognitive processing enables us to facilitate reading comprehension. Our reading accelerates and our memory increases. Likewise, when we fail to empathize with a target, such as a film, we evoke a perception of dissimilarity. This creates the opposite effect, and our cognitive processing is inhibited: we lose focus easily, finding it difficult to recall the plot of the film.1

Our enhanced cognitive processing is a result of empathy, which arises from our perception of similarity. This affects the way we interact with other individuals, as the perception of similarity can implicitly evoke empathy between two individuals. The perception of similarity is the reason why an employee may be able to learn new techniques more quickly when assisted by a mentor they empathize with.

Understanding the similarity hypothesis can allow us to better design inclusive educational curricula, particularly in scenarios where it is important to understand individuals or experiences which are not necessarily similar to most learners. This can be especially useful in cross-cultural education, history, minority education, and special-needs classes.1 Applying the similarity hypothesis in these fields of education can help overcome the effort involved in understanding experiences or individuals which are dissimilar.


Despite the repeated evidence upholding the similarity hypothesis, one criticism is that individuals frequently seek novelty and difference, with such experiences providing just as much certainty when it comes to self-evaluation.3

Scholars who disagree with the similarity-attraction theory tend to adopt the complementarity view of attraction. This view states that individuals are more likely to prefer partners who have attributes that are complementary, rather than those who possess replicating attributes. This can be seen when an individual with a certain perceived negative attribute, such as impatience, is more attracted to someone who does not possess that same attribute. The complementarity view of attraction suggests that individuals prefer not to be reminded of their faults by being with someone similar, and therefore they are more attracted to those who will complement and bring out the best in them.5

Emerging studies are also starting to define more clearly that it is perceived similarity, rather than actual similarity, that influences attraction. A 2012 study by American psychologists at Texas A&M and Northwestern University found that, unlike previous findings, actual similarity did not predict romantic attraction as effectively as previously thought.9

There are alternative views when addressing how the similarity hypothesis influences opinion comparisons between individuals. Some argue that comparisons with other similar individuals depend on the type of opinion being evaluated. A study in 2000 by Jerry Suls, René Martin, and Ladd Wheeler highlights results which suggest that we prefer comparing with other similar individuals when it comes to the evaluation of preferences. Think about how you are more likely to care about what your best friend thinks of your outfit, compared to the Lyft driver who dropped you off this morning. In contrast, other studies have suggested that we prefer to compare ourselves with dissimilar individuals when it comes to belief assessment,3 such as evaluating whether a certain statement or proposition is true.

Case Study

The effects of the similarity hypothesis on memory retrieval.

In 2015, Hidetsugu Komeda conducted a study to observe memory retrieval in typically developing (TD) individuals and individuals with Autism Spectrum Disorder (ASD). The similarity hypothesis predicts that individuals with ASD will be able to easily retrieve other individuals with ASD from their memory. Participants were carefully selected and read 24 stories, before completing a recognition task. The results showed that ASD individuals demonstrated the same level of accuracy as TD individuals, but memory-retrieval patterns between the two groups were different.1

Individuals with ASD were able to retrieve ASD-consistent stories more easily than ASD-inconsistent stories. TD individuals were also able to retrieve TD-consistent stories more easily than ASD-protagonist stories. These results are consistent with the similarity hypothesis, suggesting that individuals with ASD characteristics are able to help other ASD individuals due to empathy arising from their similarities.1

Related TDL Content

The Similar-To-Me Effect

Why do we tend to surround ourselves with people similar to ourselves? While it is normal to get along with people who have similar experiences, like your basketball teammate or a fellow college alumnus, favoring people similar to you becomes a problem when it leads to discrimination.

Why do we feel more strongly about one option after a third one is added?

You might never buy the most expensive option, but do you sometimes buy the second-most expensive option? The decoy effect explains why the addition of a third choice can make us spend more money – even if we don’t opt for the new choice.


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About the Author

Joshua Loo

Joshua was a former content creator with a passion for behavioral science. He previously created content for The Decision Lab, and his insights continue to be valuable to our readers.

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