Unconscious bias works quickly and below awareness. A recruiter may warm to a candidate who went to the same university, which is affinity bias, or let one impressive detail colour the whole assessment, which is the halo effect. The horn effect is the reverse, where one negative detail drags everything down. Names, accents, employment gaps and photos can all trigger these shortcuts.
Awareness training on its own has a mixed record of changing behaviour, so the more reliable fix is process design. Defining criteria before reviewing anyone, asking every candidate the same questions, scoring each answer separately and hiding details that are not job-relevant all narrow the space for bias. Automated tools can repeat bias found in historical data, so they need regular checks too, with people reviewing outcomes and making decisions.