Assumed Similarity Bias

What is assumed similarity bias?

Assumed similarity bias occurs when people perceive others as more like themselves than they actually are. The broader term assumed similarity describes judgments of another person that reflect one’s own characteristics; those judgments are not necessarily inaccurate. It is related to, but broader than, the false-consensus effect concerning how widely one’s views or behavior are shared.

What the research found

Thielmann, Hilbig, and Zettler’s 2020 paper combined a meta-analytic summary with nine studies of personality judgments among strangers. Assumed similarity was strongest for Honesty-Humility and, more weakly, Openness to Experience.

The findings supported a link with personal values. They did not show consistent assumed similarity across all traits, even with little information about the person being assessed.

Example of assumed similarity bias

Imagine a manager who values public recognition and assumes a colleague wants the same kind of praise. If the colleague would prefer a private thank-you, the manager has mistaken a personal preference for knowledge of the other person.

Why it matters

Your own preferences are easy to consult. Another person’s may take work to understand. Check what you assume against what you know about that individual, particularly when a judgment concerns values that matter strongly to you.

In these studies, actual similarity and shared group membership did not explain the results. That makes the trait-specific pattern more informative than a broad claim that people assume others resemble them in every respect.

The similar-to-me bias concerns favoring people perceived as similar to oneself.