How we change what others think, feel, believe and do
When we believe we are showing bias (or are likely to do so), our efforts to neutral easily end up with us displaying bias in the opposite direction.
In this way, people who are trying to be 'politically correct' end up breaking their own rules of equality.
Another difficult situation where bias correction occurs is where juries actually either put extra emphasis on evidence that is ruled inadmissible or over-compensate in the opposite direction.
Petty et al (1998) asked subjects to avoid letting their biases about an unpleasant person influence their judgements of the person's persuasive efforts. The subjects ended up being more persuaded by the person's efforts than when they were presented by a likeable person.
A manager who has a new disabled member of staff working for them, and is concerned to treat them fairly, ends up spending more time with that person than with other members of staff and also is more lenient with them during personal performance assessments. This does not help the relationship that the disabled person has with other people in the department.
To get a person to offer bias towards a person or argument, tell them that they are being biased against from the person or argument. Indicate that this is a bad thing.
When you know you may show bias or overcompensate in the opposite direction, pause to consider objectively if you are truly being neutral. If in doubt, as somebody else.