What Is Rater Bias and How Does It Affect Performance Reviews

Rater bias in performance reviews

In this short series on performance management, we explore some of the lesser known facets of it. In this article, we explore the different kind of rater biases that exist and how they affect the performance review process.

Rater Bias

Rater bias can be defined as an error in judgment that can occur when a person allows their preformed biases to affect the evaluation of another. Rater biases are a common issue when it comes to performance reviews. They are a hazard of rating systems and cannot be truly eliminated.

There are many different kinds of rater biases. Here is a list of some of the most common biases that occur when it comes to performance reviews.

Leniency Bias

The Leniency bias occurs when a person receives inflated ratings because they rater is feeling sympathetic towards them for whatever reason.

Central Tendency Bias

The Central Tendency Bias occurs when a rater give everybody an average rating despite their actual performances. Here, raters are disinclined to give people a low rating or a high rating, preferring instead to give an average, middle rating.

Strictness Bias

The Strictness Bias occurs when raters give people ratings that are overly critical and fall at the lower end of the rating scale. So small mistakes will be treated as inexcusable mistakes and rather taking into account the overall performance of a person, the rater will look at each instance and evaluate strictly based on that.

Contrast Bias

The Contrast Bias tends to occur when raters evaluate a person by comparing them to a previous person who was in the same position. This effect can be either positive or negative depending on the person who previously held the position.

False Attribution Bias

The False Attribution Bias occurs when raters assume that people are in complete control of their successes and failures.

Similar To Me Bias

The Similar To Me Bias occurs when raters rate people more positively simply because the person being rated is similar in personality and behavior to the rater.

Personal Bias

We are all guilty of personal biases. Sometimes they are conscious, sometimes they are unconscious. Personal biases can take the form of gender bias, religious bias, political bias etc. They are one of the worst form of biases because all of them have nothing to do with an employee’s performance in the workplace.

The Halo/Horns Effect

The Halo Effect occurs when a rater evaluates people based on only one good aspect of theirs and disregards the other factors of their performance, whether they are good or bad.

Conversely, the Halo Effect occurs when a rater assumes that a person’s performance must be entirely bad, because the rater chooses to focus on one bad aspect of the person’s performance.

How does rater bias affect performance reviews?

Rater bias can skew performance reviews either negatively or positively regardless of an employee’s actual performance. And while an employee can control how he performs his job, he has no control over a rater’s bias against him.

It has been shown that the vaguer the questions in a performance review, the easier it is for raters to let their biases influence them. When raters have to answer specific questions, which are rooted in competencies or numbers, they are able to give answers that are relatively free of bias.

As we mentioned before, rater bias is inevitable and can never be completely eliminated. However, raters can be taught to be consciously mindful when undertaking performance reviews.  Each time a rater reviews a person’s performance, they need to ask themselves about why they are rating them, are their ratings motivated by bias, does the person deserve the rating etc.

Getting rid of unconscious bias will sometimes be a slow and painful process, but that does not mean that people are incapable of evaluating others in a fair and impartial manner.


Engagedly is a performance management platform with elements of employee engagement. To see how we can help your organization improve the performance review process, request a demo today!

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