Can you discriminate a line?

In my last post, we discussed how groups function differently from individuals. But, how are groups formed? And, how do stereotypes (attributions of characteristics to a group) and prejudices (attitudes towards a group) arise? Tajfel and Wilkes addressed these topics through a unique experiment.

Sixty-one English students were recruited to assess the length of 8 lines. The shorter line measured approximately 16 centimeters, while the longer line measured about 23 centimeters. The lines were the same color but differed in length, making it possible to sort them from shortest to longest.

The students were then asked to answer the following question: 'In your opinion, how long is this line?' They had to make 6 judgments for each line and repeat all of their evaluations at a distance of one week.

The lines were presented under two different conditions. In one condition, the lines were presented with a letter accompanying them, specifically the letter A with the four shorter lines and the letter B with the four longer lines (categorization condition). In the other condition, the lines were presented without any labels (random condition).

What do you think happened? In the categorization condition, students considered the four shorter lines and the four longer lines to be more similar to each other than they actually were. Moreover, if we take the fourth and fifth lines in order of length as a watershed between the short and long lines, they were perceived as more different than they actually were.

What does this mean? A simple label was enough to define two groups - the letter A represented one group, and the letter B represented the other. If such "simple" stimuli can create distinct groups, imagine what happens in the real world, where we are bombarded with stimuli (physical, social, and behavioral).

For example, skin color and human physiognomy vary from person to person, but they are also similar among people with similar geographical origins. Therefore, our brains tend to group people with similar physical traits together and separate them from others.

If these groups also exhibit different behaviors, our perception of the differences between "us and them" becomes stronger. Negative experiences with someone from a different group can lead to a negative labeling of that group, which is called prejudice. Discrimination is the next step - negative behavior directed towards a group other than one's own.

What are your stereotypes and prejudices? When did you create them?
For example, while I used a language exchanging app, I had some negative experience with people who came from a foreign country. For a period of time, I no longer took the initiative towards other people with the same geographical origin.

If you want me to describe in my own words a topic of psychology, please request it in the comment section.

Cited sources: Tajfel & Wilkes (1963) - Classification and quantitative judgement.