Halo Effect

The halo effect refers to an error in reasoning where an impression formed due to a single trait is allowed to influence multiple judgments or ratings of unrelated factors. For instance, the halo effect operates when a rater forms a general impression of another person, based on one outstanding trait, and that general impression is allowed to influence judgments or ratings that should instead be based on specific aspects of the person. For example, people who are attractive may also be judged to be good workers without regard to their actual work performance; the positive impression of their attractiveness clouds the rater's ability to judge the actual quality of their work, although these two traits are not related. These overall impressions misrepresent the specific traits a person may have because they are based on a small amount of information.

The American psychologist Edward L. Thorndike (1874–1949) was a pioneer in studying the phenomenon of the halo effect. For instance, it was clearly present in an experiment conducted with servicemen in 1920, which was reported in his article ‘A Constant Error on Psychological Rating.’ In the experiment, the commanding officers were asked to rate their subordinates on their intelligence, physique, leadership, and character without having spoken to them. Thorndike noted a correlation between unrelated positive and negative traits. The service members who were found to be taller and more attractive were also rated as more intelligent and as better soldiers. Thorndike determined from this experiment that people generalize from one outstanding trait a person has to form a favorable view of the person's whole personality.

Another psychologist who studied the halo effect was Polish American Solomon Asch (1907–1996). In his 1946 article ‘Forming Impressions of Personality,’ Asch delineated how people form impressions of one another. Asch found that impressions of others were formed by a ‘primacy effect.’ First impressions were established as more important than subsequent impressions in forming an overall impression of someone. Participants in the experiment were read two lists of adjectives that described a person. The adjectives on the list were the same but the order was reversed; the first list had adjectives that went from positive to negative, while the second list had the adjectives in reverse order, from negative to positive. How the participant rated the person depended on the order in which the adjectives were read. Adjectives presented first had more influence on the rating than adjectives presented later. When positive traits were presented first, the participants rated the person more favorably; when the order was changed to introduce the negative traits first, that person was rated less favorably.