People tend to do what others around them are doing. Walk onto an elevator and almost everyone stands facing forward. People in conversation tend to match each other’s speech rate, and even the pitch of their voices.

The judgments made by a group also tend to converge. The classic version of this conformity effect comes from studies by Solomon Asch first conducted in the 1950s. Participants were members of a group who were judging the length of lines. On some trials, the group made judgments that were wrong by a large margin. When participants judged the length of that line again in the future, they generally biased their judgment in the direction of the group, even though they thought the group was probably wrong.

Social forces influence people’s judgments. People want to belong to a group, or want to avoid disagreeing with others, and so they modify their judgments to fit in more with what the group says. Diana Kim and Bernhard Hommel suggest in the April, 2015 issue of Psychological Science that these conformity effects may also arise naturally from the way that people represent the events that go on around them.

When people observe an event happening around them, they understand it in part by using the same brain areas that they would use to prepare to perform that event. Afterward, it may be difficult to distinguish between events that they observed and events that they performed, because both involved information about the specific movements that would be made to perform that action.

To explore this idea relative to conformity, the researchers had participants rate the attractiveness of a large set of faces. Participants made ratings twice over the course of the study by typing a number with a keyboard. After each trial, participants saw either a number or a short video showing a hand typing a number on a computer keyboard like the one they were using. Participants were told that they would see these numbers and videos, but that they had no relationship to the faces that they were rating.

The key measure on this study is the rating people gave the second time they saw the faces. When people had seen videos of a hand typing a number, their ratings were strongly influenced by what they had seen. Overall, there was a tendency for people in general to rate the faces as less attractive the second time they saw them.

However, if the hand they’d seen in the video typed a lower rating than the participant himself or herself had given for that face, their ratings went down a lot. When the hand typed a higher number than the rating the participant had given for a face, the participant’s rating was about the same as what they had given it the first time. When the hand typed the same number as the participant’s rating for that face, the second rating the participant gave came out in between what they gave for those faces where the video hand’s entered number was higher or lower than their initial rating.

This pattern of ratings for the second pass through the pictures reflects a conformity effect: Just seeing numbers did not produce a conformity effect; when they just saw numbers after each face, there was very little impact on the second ratings of the faces. Seeing the hand proved to be the key.

In another study, participants rated faces and saw numbers after each one, but now they were told that those numbers were the average rating for that photo by students at their university. In this version of the study, there was a conformity effect, but the margin of the influence of these numbers was smaller than what was observed in the study with the videos.

When people explicitly represent the actions of another person (such as the video of the hand), that creates something that looks like the classic conformity effect. The effects of watching another person performing an action is at least as strong as finding out the judgments of another group of people.

Many of these results may reflect the memories people have of other people’s actions, because those memories both involve areas of the brain responsible for action planning. At first, it might seem strange that people would confuse their own actions with the actions of others. Only recently in our evolutionary history would it matter whether our memories reflected something we did ourselves or something we observed. Culturally, we care a lot about assigning blame to particular individuals for actions. For most other species, though, it does not matter in the long run whether particular animals have detailed memories of exactly who performed what action in the past.

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