What Is The Recency Bias?
There is a tendency for some people to focus on "what's happened lately" when evaluating or judging something. It's the same in performance reviews. Some managers tend to weight what the employee appears to have done in the last weeks or months, rather than looking at the entire period evaluation is supposed to be based on.
There is some sense to doing this, however. One could argue that an employee who shows recent improvement is on the road to success, and therefore should not be penalized by things that happened, let's say 10 months ago. It's a decent argument.
However, if the desire is to improve productivity, rather than to reward or punish, it IS useful to discuss past problems to try to ensure they don't re-occur.
The recency bias can also work both ways. Remember that recent behavior can be positive or negative, so managers stuck with the recency bias may be evaluating overly positively or negative, depending on what's most recent.