The halo effect often starts with a single eye-catching detail: a well-known university, a previous role at a famous brand or a polished, confident first few minutes of an interview. Interviewers then rate unrelated qualities, such as technical depth or teamwork, more generously than the evidence supports. It can also run through a CV, where an impressive opening line colours how the rest is read.
Unchecked, the halo effect rewards presentation and pedigree over ability, and it can disadvantage capable candidates from less familiar backgrounds. Scoring each criterion separately against defined anchors, writing down evidence before giving an overall rating and having more than one assessor all reduce its pull. Structured interviews help because every candidate answers the same questions, so one impressive moment carries less weight.