Social Group Prejudice

Milgram's Lost Letter Experiment

Oskar Blakstad50.8K reads

Milgram's Lost Letter Experiment

Classic social psychology experiments are widely used to expose the key elements of aggressive behavior, prejudice and stereotyping. Social group prejudice is manifested in people's unfavorable attitudes towards a particular social group.

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Stanley Milgram's Lost Letter Experiment displays this prejudice towards a social group and its members.

Research Problem

Stanley Milgram's Lost Letter Experiment is a technique Milgram devised to examine the prejudice toward socially undesirable groups. Milgram developed this to measure and find out how helpful people can be to strangers who are not present, as well as their attitudes towards different groups.


Stanley dispersed 400 sealed, stamped and self-addressed envelopes in public places. The 'lost letters' were addressed to various entities including individuals like Mr. Walter Carnap, favorable organizations such as medical research institutes, and others like friends of the Communist party and friends of the Nazi Party. A hundred envelopes were addressed to each of the groups.

The envelopes presumably containing letters or donations are 'lost' throughout the designated area but nevertheless abandoned. They were dispersed in the streets, under car windscreen wipers, telephone booths, and in shops. Those who found the letters could post it, ignore it or even destroy it.


Since the rate of return is the focus of Milgram's study, it was recorded that more people mailed letters addressed to the socially desirable groups, which included those of the medical associates and the personal letter, than the socially undesirable groups like the Nazi party and the Communist party.

The medical research associates had the rate of return of 72%, the personal letter 71%, and only 25% for each for friends of the Nazi Party and friends of the Communist Party. Most of the letters for the friends of Nazi Party and friends of the Communist Party were never seen again.

One interesting finding in Milgram's experiment is that 40% of the letters to the Communist Party, 32% of the Nazi Party, 25% of the Medical Research letters, and 10% of the letters to Walter Carnap had been opened.


The results of the experiment suggest that there is an existing prejudice between different social groups. The experiment is significant as it allows prejudice to be investigated through an everyday task, where people do not realize that their prejudice is being examined, thus making it more valid and reliable.

Social group prejudice and stereotyping are actually difficult to evaluate due to social desirability, and people are not usually willing to share and express or even admit their discriminatory views of other social groups.

Milgram's Lost Letter Experiment provides for an easy evaluation and assessment of the phenomenon social group prejudice by hiding the motivation behind the lost letter. This technique was used to predict the Johnson-Goldwater election. To date, this technique has become widely used as a non-reactive measure of societal attitudes.


The Classic Experiments of Aggression, Prejudice and Stereotypes in Social Psychology by Bec Blair

Wikipedia: Stanley Milgram

Stanley Milgram

Full reference: 

Oskar Blakstad (Sep 14, 2010). Social Group Prejudice. Retrieved Sep 25, 2023 from Assisted Self-Help: https://staging.explorable.com/en/social-group-prejudice