In a famous Pennsylvania study, 74 male defendants with similar backgrounds and crimes were found to have received very different sentences, based upon their appearances. Which social psychology concept best explains these results?

Stewart (1980) Halo Effect.

Explanation:

The halo effect refers to a form of cognitive bias in which our general opinion of an individual determines how we think or feel about their personality. When creating a first impression, noticing an initial desirable characteristic, maybe attractiveness or power may make the individual appealing, making it difficult to revise the impression on the basis of new or opposing details. As per the question, the different analyses of defendants for the same crime is an example of the Halo Effect.