People often notice when a woman is the lone female expert in a group. But do they notice when women are missing entirely? New research suggests the answer is often no.

A series of field studies and experiments with over 1,500 participants, published in the Proceedings of the National Academy of Sciences (PNAS), found that people frequently overlook the absence of women and racial minorities. Whether an article quoted no women experts or conference attendees heard only from non-Black speakers, many people didn’t notice until someone asked them about it. The researchers explain that when we don’t necessarily expect to see someone in a particular setting, we often don’t notice their absence.

They label this tendency “blindness to minority absence” and explain in their paper why this can be a real problem: “Because people cannot act on problems they do not perceive, blindness to minority absence may present a significant obstacle for the development and effectiveness of diversity-promoting policies.”

In one of the experiments, participants read an article about cerebral strokes that included quotes from six neurosurgeons. In one version, all six neurosurgeons were men, and in the other, five were men, and one was a woman. When all six experts were men, only about 17% of participants noticed the absence of women while reading the article. But when just one of the six neurosurgeons was a woman, participants were much more likely to notice her presence. Interestingly, many participants who had not noticed the lack of women while reading the article were able to recall that no women had been included when researchers specifically asked them about it.

The researchers found a similar pattern with race. Participants were more likely to notice Black faces when they appeared in a set of images than when they were missing from the set.

The opposite happened with white faces. People were more likely to notice when white faces were missing. In one study, participants were 14 times more likely to notice when white faces were absent than when Black faces were absent. Because participants expected to see white faces, their absence stood out.

This blindness was not limited to women and racial minorities. Participants were generally more likely to notice when the group they expected to see in a particular setting was missing. For example, in kindergarten classrooms, people typically expect to see female teachers. So, in one experiment, participants were more likely to notice if a kindergarten classroom had no female teachers than if it had no male teachers.

Surprisingly, even people who belonged to the underrepresented groups often failed to notice the absence of members of their own race or gender. And the political beliefs of the participants played no role in whether participants recognized these absences.

Instead, the reason people overlook missing groups is related to how the brain processes information. We tend to notice things that are unusual, but we don’t notice things that fit our expectations. In their paper, the researchers illustrate how this tendency works with an example about noticing items in a kitchen: “Noticing the absence of an office chair or recliner every time one enters a kitchen is as unlikely as it is inconsequential. On the other hand, it is more likely and consequential that one would notice the absence of an oven in a kitchen, and if one happens to come across a recliner in a kitchen, they are very likely to notice it.”

To our brains, a female neurosurgeon is unexpected, much like a recliner in a kitchen. The concern is that when people don’t notice who is missing, they are less motivated to push for more diversity.

Interestingly, when participants were prompted to reflect on whether women or minorities were missing, they often remembered correctly. But without the extra push to consider who was absent, the absences went unnoticed. Rasha Kardosh, a postdoctoral fellow at New York University and the lead author of the paper, explained in a press release why this is an important nuance: “This bias in perception can mask inequality and make our environments appear more diverse than they truly are. Simply prompting people to ask ‘Who is missing?’ may change how they see a setting and how they think about possible responses.”

These research findings come at a time when diversity initiatives are facing increased scrutiny. A push to have coworkers consider who is missing from different situations may help people realize why these efforts are still needed.