Warning - Jargon Alert! The following article contains some... But of course you won't be using any at the interview!
Primacy and recency biases: Research indicates that interviewers tend to remember the start and end of the interview but are somewhat vague about the middle, so a strong starting and ending performance is important.
The primacy effect becomes transformed into the expectancy effect where the interviewer forms an expectation of the candidate from their application form and initial verbal and non-verbal behaviour. These early impressions strongly affect the final appointment decision.
The contrast effect indicates that the interviewer's decisions are affected by those whom they have seen before you. They pay particular attention to any information (good or bad) that is unusual or out of the ordinary.
The personal liking bias suggests that interviewers select people they like and they allow their ratings of a candidate’s ability to be affected by such liking. The greater the perceived similarity between yourself and the interviewer, the more they will interpret your behaviour as reflecting attitudes that are similar to their own.
The interviewer’s confirmatory information-seeking bias may lead them to actively look for evidence to support their initial impression and thereby to avoid contradictory evidence.
It is important to give good explanations for any less than positive elements of your career history or CV. This is because people assume that we deserve our status, success, rank, etc. Similarly we assume that others are less fortunate because they deserve to be (“people get what they deserve”). The effect is that unless you use such explanations appropriately you will be blamed for your perceived failures. Remember that negative information about a candidate disproportionately outweighs positive information, particularly if this impression is given early in the interview.
Many employers will seek to overcome these biases in order to be more objective and fair to candidates. They may use structured and competency based interviews, and involve two or more interviewers. This helps to reduce the impact of these biases to some degree although it should be noted that they will still be in operation.