Performance reviews are intended to be fair, structured, and evidence-based. In practice, they are shaped by human judgement, and that means they are also influenced by bias.

Most bias in performance reviews is not intentional. It shows up subtly, through everyday habits and decisions that feel reasonable in the moment.

In day-to-day work, this can be seen in how managers recall performance.

An employee who recently handled a visible issue well may be rated more highly, while consistent performance over several months is overlooked. Another who made an early mistake may continue to be viewed through that lens, even after improving. These are examples of recency bias and anchoring, both common cognitive patterns.

Research in behavioural science, including the work of Daniel Kahneman, shows that people rely on mental shortcuts when making judgements, especially under time pressure. In the context of performance reviews, this can lead to decisions that feel accurate but are not fully balanced.

Bias can also appear in how different behaviours are interpreted.

For example, assertiveness in one employee may be seen as confidence, while in another it may be perceived as difficult or disruptive. Communication style, tone, and personality can influence ratings, even when they are not directly linked to role requirements.

Work by Alice Eagly highlights how expectations and stereotypes can shape these interpretations, particularly in relation to gender. Similar patterns can apply across other characteristics, influencing how performance is evaluated and discussed.

Another common pattern is similarity bias.

Managers may, without realising it, rate individuals more favourably when they share similar working styles, backgrounds, or approaches. This can affect not only ratings but also opportunities for development and progression.

In everyday review conversations, bias often appears in the language used.

Feedback may be more detailed and specific for some employees, while others receive broader, less actionable comments. Some are evaluated based on potential, while others are assessed strictly on past performance. Over time, these differences can compound.

Importantly, these patterns are rarely deliberate. They are the result of fast decision-making, limited time, and incomplete information.

There are practical ways to reduce their impact.

Using specific examples across the full review period, rather than relying on recent memory, helps create a more balanced view. Comparing performance against clear, role-based criteria, rather than personal expectations, reduces subjectivity.

Structured calibration discussions can also help. When multiple perspectives are involved, inconsistencies are more likely to be identified and addressed.

Language matters as well. Focusing on observable behaviours and measurable outcomes, rather than personality traits, improves clarity and fairness.

Finally, slowing down the decision-making process can make a significant difference. Bias is more likely to influence quick judgements. Taking time to reflect, question initial impressions, and review evidence helps create more consistent outcomes.

Performance reviews play a key role in shaping careers.

Understanding how bias can unintentionally influence them is not about assigning blame. It is about improving the quality of decisions and ensuring that performance is recognised in a way that is fair, consistent, and evidence-based.