Halo Effect
A cognitive bias where overall impression of a person influences ratings of their specific traits. High Halo causes traits to correlate artificially in observer ratings.
The Halo Effect (Thorndike, 1920) distorts personality ratings: if a manager likes an employee overall, they tend to rate that employee higher on every specific trait — including traits the manager has no real evidence about.
This is why 360-degree feedback often shows artificially high inter-trait correlations: raters anchor on overall impression rather than discriminating between competencies. The effect is strongest for less-observable traits (judgment, integrity) and weakest for clearly behavioural ones (punctuality, output volume).
Good test design fights Halo through: forced-choice formats (rate-which-is-more-like-you rather than rate-each-on-a-scale), behavioural anchors with specific examples, and structured rather than open-ended observation.
Source: Thorndike, E. L. (1920). A constant error in psychological ratings. Journal of Applied Psychology.