Social pressure changes an individual's judgement to stay in accordance with the group opinion, but the effect lasts only for three days, according to a South China Normal University study.

The phenomenon of personal judgments being influenced by others' believes is a well-established fact in psychology research. But the new research points out that the effects of social pressure, too, have an expiry date.

"Our findings suggest that exposure to others' opinions does indeed change our own opinions - but it doesn't change them forever," said psychological scientist and study author Rongjun Yu of South China Normal University, in a statement. "Just like working memory can hold about 7 items and a drug can be effective for certain amount of time, social influence seems to have a limited time window for effectiveness."

Previous studies have already established a relationship between public opinion influence and personal judgement; the researchers haven't yet determined whether the link exists due to personal acceptance, public compliance, or their enthusiasm to fit into a group.

To better understand this link, the Chinese researchers examined the perception of college students to facial attractiveness. The students were shown about 280 photos of Chinese women and asked to rate them according to their attractiveness on a scale of one to eight.

The rating of each face was then compared to the average ratings of 200 other students. The group average matched the participant's rating only 25 percent of the time. On other occasions, the group's average was 1, 2, or 3 points above or below the participant's rating.

The participant's were again asked to rate the photos after 1 day, 3 days, 7 days or 3 months of the initial rating session. Researchers found that that group ratings affected a participant's rating when the second rating session took place after one to three days. However, no influence was observed when participants scored the pictures after more than three days of the first session.

Researchers were, however, not able to find out the reasons for the three-day expiry date. Researchers are planning to understand the mechanism in their further studies.

The finding is published in the Association for Psychological Science (APS) journal Psychological Science.

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