black sheep

In the English language, black sheep is an idiom used to describe a member of a group, different from the rest, especially within a family, who does not fit in. The term stems from sheep whose fleece is colored black rather than the more common white; these sheep stand out in the flock and their wool was traditionally considered less valuable as it was not able to be dyed.
The term has typically been given negative implications, implying waywardness.In psychology, the black sheep effect refers to the tendency of group members to judge likeable ingroup members more positively and deviant ingroup members more negatively than comparable outgroup members.

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