2.8 Aspects of unconscious bias: confirmation bias

One factor which can exacerbate our stereotypes and undermine decision making is confirmation bias, as we have a natural tendency to be selective in the evidence we listen to and the evidence we disregard.

Confirmation bias works like this: You meet someone and unconsciously categorise or judge them. The stereotypes and societal norms linked to those categories are linked to that individual.

You are more likely to notice and remember their behaviour which is in keeping with the stereotypes/categories into which you have placed them – thereby reinforcing your opinion of them in that category. You are proving yourself to be correct.

You are less likely to notice and remember their behaviour which does not fit within the stereotype or category.

Confirmation bias exists because our brains are designed to think that we are right and to look for information that endorses or confirms our beliefs. So investors and financial managers are often over confident about stocks that they have picked, as they are biased towards seeking out and interpreting evidence in a way that confirms their original, positive assessment and decision to buy the stock.

Once we have made even a small judgement or decision, our brains start looking for evidence to confirm it.

Activity 6

Watch this video for an interesting example of confirmation bias: https://www.youtube.com/ watch?v=vKA4w2O61Xo [Tip: hold Ctrl and click a link to open it in a new tab. (Hide tip)]

The clip demonstrates that people often try to interpret evidence in a way that confirms their original assessment (confirmation bias), rather than using the information we gather to challenge our assumptions.

Activity 7

How might confirmation bias relate to gender equality or gender stereotypes? How could it affect teachers in a school or classroom environment?


A finding in educational research is that teachers spend a disproportionate (roughly 2/3rds) amount of their time talking to male pupils and are more likely to prompt, praise and encourage male pupils, and give them space during and in front of the class. These differences aren’t intentional, but often the result of confirmation bias. Teachers are aware of gendered stereotypes in relation to assertiveness and performance in certain subjects. Teachers may unconsciously look for or encourage participation from male pupils, and ignore or discount similar signs from female pupils. Crucially, teachers are unaware of what’s happening and believe they are being equal to male and female pupils, until they view their videotaped classes.

This article goes into more detail on a recent study from Israel by Lavy and Sand (2015), which describes a different way in which confirmation bias can lead to differences in performance between girls and boys, and subsequent course choices. These researchers ran an experiment using students, one math test, and two sets of math test scores.

One set of scores were given by the classroom teachers, who obviously knew the children whom they were grading. The second set of scores were from external teachers who did not know if the children they were grading were either boys or girls. So the external teachers were blind to the gender of the children.

The classroom teachers tend to give the girls lower grades in math than the external teachers, and they give the boys higher grades. Now, since the external teachers don't know the gender of the students, this suggests the classroom teachers are biased. They're giving the girls lower math grades than they deserve.

The researchers then tracked the same children into high school and this different treatment and experience discouraged girls from pursuing to high level courses in science and mathematics, and had the opposite effect on boys.

While we are focused on women and STEM, confirmation bias has the same, opposite effect on male pupil performance in reading, arts and language. Teachers grade male pupils more harshly and female pupils more leniently in these subjects, which further biases the subjects pupils think they are good at, and which they then want to study further in.

2.7 Understanding different types of unconscious bias

2.9 Aspects of unconscious bias: stereotype threat