What effect occurs when raters evaluate individuals based on a single positive or negative recent incident?

The phenomenon described in the question is accurately identified as recency bias. This effect occurs when raters give disproportionate weight to recent incidents—whether positive or negative—over an individual's overall performance or behavior. As a result, if a rater remembers a particularly notable recent event, it can skew their evaluation of that individual, leading them to form opinions based more on that incident than on a comprehensive view of the person’s conduct or achievements over time.

Recency bias can significantly influence performance appraisals and other evaluations, as raters might overlook past behavior or performance that does not align with the most recent information they have encountered. This focus can create an unfair assessment, either overly favorable or overly critical, depending on whether the recent incident was positive or negative.

This concept emphasizes the importance of considering a broader range of performance data to ensure fair and accurate evaluations, reinforcing the necessity of adopting comprehensive evaluation criteria that reflect the full scope of an individual's performance rather than allowing a single recent incident to dominate the assessment.