7 Types of Interview Bias (and How to Prevent Each One)

1. Halo Effect

What it is: One positive characteristic colours your assessment of all others. The candidate is eloquent, so you assume they're also operationally strong.

Prevention: Score each competency independently before forming any overall impression. Use a scorecard that forces discrete assessments.

2. Horn Effect

What it is: The reverse of halo. One negative characteristic — nerves, poor eye contact, an awkward answer early on — poisons the rest of the assessment.

Prevention: Treat each question as a fresh assessment. Pre-agree that nerves in an otherwise strong answer deserve acknowledgment in your notes, not a lower score.

3. Affinity Bias

What it is: We favour candidates who are similar to us — same background, same style of communication, went to the same university, support the same football team.

Prevention: Standardised questions that focus on evidence, not rapport. Scoring against criteria rather than overall impression. Diverse interview panels.

4. Confirmation Bias

What it is: We form an impression quickly and then seek confirmation rather than challenge. Interviewers in unstructured interviews unconsciously steer conversations towards confirming their first impression.

Prevention: Pre-set questions prevent steering. Score after the answer, not after the interview. Deliberately note evidence that contradicts your initial impression.

5. Contrast Effect

What it is: We assess candidates relative to each other rather than against an absolute standard. An average candidate looks excellent after a weak one. A strong candidate looks weaker after an exceptional one.

Prevention: Scoring rubrics define an absolute standard. A 3 means "meets the criteria" regardless of who came before.

6. Recency Bias

What it is: We remember what happened most recently more vividly than what happened earlier. The last answer in an interview influences the overall impression disproportionately.

Prevention: Score each answer immediately after it's given, not at the end of the interview. Notes taken during the conversation anchor you to what was actually said.

7. Attribution Bias

What it is: We attribute success and failure differently to in-group and out-group members. For candidates we like, successes are attributed to their skills; for those we don't, successes are attributed to luck or circumstances.

Prevention: Standardised probing questions (e.g., always ask "what was your specific role in that?") prevent differential attribution.