What Is Rater Bias and How Does It Affect Performance Reviews

by Srikant Chellappa Apr 10,2022

The People Strategy Leaders Podcast

with Srikant Chellappa, CEO

What is Rater Bias?

Rater bias is defined as an error in judgment that can occur when a person allows their preformed biases to affect the evaluation of another. It is a common issue when it comes to performance reviews in organizations. It can severely impact the effectiveness of a performance review as it can distort the ratings and result in inaccurate performance evaluations. It is a hazard to rating systems and cannot be truly eliminated

There are many different kinds of rater bias in performance appraisal. The below list highlights the most commonly known ones that employees encounter during their performance review process.

Types Of Rater Bias In Performance Appraisal

Check out the below rater biases that can impact performance review and appraisal processes in an organization.

Leniency Bias

The leniency bias occurs when an employee receives inflated ratings because the manager feels sympathetic towards them for whatever reason. Leniency bias impacts the overall productivity, trust, and engagement level of the whole team. Most of employees have experiences most sort of leniency bias in their work tenure.

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. This sort of bias can severely hamper the productivity of the team. The high-performing employees after receiving an average rating would not want to contribute as they used, leading to lower quality output and diminishing results.

Also read: Leadership In Times Of Crisis: How To Lead Effectively 

Strictness Bias

The strictness bias occurs when a manager or a rater gives employees ratings that are overly critical and fall at the lower end of the rating scale. The overall performance of an employee is overlooked and even the smallest of mistakes is treated as critical by the rater. Other than reducing the performance level, strictness bias can hamper the decision making process of employees and inhibit them from innovative and critical thinking.

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. Many employees fall prey to contract bias and have to manage it inaccurate ratings.

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. Managers are often inclined to employees whose personalities, work methodologies, and approaches are similar to them. Hence, they tend end up providing inaccurate review of employees’ performance.

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.

Also Read: Everything You Need To Know About Handling Employee Complaints

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 horns 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.

Both halo and horns effects hamper the fundamentals of a performance review process. By focusing on only the good and the bad, raters tend to miss out on important aspects of employees’ performance.

How Does Rater Bias Affect Employee 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 they performs their job, they have no control over rater’s bias.

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. Another way of removing bias from performance

Getting rid of unconscious bias will sometimes be a slow and tedious process. But that does not mean that people are incapable of evaluating others in a fair and impartial manner. With proper training, understanding, and discussion, employers can help remove rater bias from their performance review process.

Employee Engagement

Frequently Asked Questions

Q1. What is rater bias?

Ans. Understanding rater bias is important for accurate employee evaluations. Rater bias includes halo bias, where a rater gives overly positive ratings based on strong performance; horns bias, where a rater gives overly negative ratings based on poor performance; and primacy bias, where a rater forms an opinion early in the evaluation process.

Q2. Why is rater bias a problem?

Ans. Rater bias can affect the validity and reliability of assessments, evaluations, and research studies. It can also lead to unfairness and discrimination in decision-making processes, particularly in areas such as hiring, promotion, and academic grading.

Q3. What are some common types of rater bias?

Ans. Some common types of rater bias include leniency bias (overrating performance), strictness bias (underrating performance), central tendency bias (rating most individuals as average), halo effect (generalizing positive or negative impressions across different aspects of performance), and recency bias (focusing on recent performance rather than overall performance).

Q4. How can we reduce rater bias?

Ans. There are several strategies that can help reduce rater bias, such as providing clear and objective criteria for evaluation, training raters on these criteria, using multiple raters to reduce the impact of individual biases, monitoring and reviewing rater performance, and using anonymous evaluations to reduce the impact of personal biases.

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Srikant Chellappa
CEO & Co-Founder of Engagedly

Srikant Chellappa is the Co-Founder and CEO at Engagedly and is a passionate entrepreneur and people leader. He is an author, producer/director of 6 feature films, a music album with his band Manchester Underground, and is the host of The People Strategy Leaders Podcast. He is currently working on his next book, Ikigai at the Workplace, which is slated for release in the fall of 2024.

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