Category labels distort the way we see faces

Categories – family or species, color or size – can bias our perception. This effect appears in widespread patterns of brain activity, according to the research.

Dasa Zeithamova’s team at the University of Oregon found that category labels could change the way people perceived faces after just a few exposures. “It’s surprising that this is happening so quickly,” says Zeithamova. She and former graduate student Stefania Ashby report their findings in the Journal of Neuroscience.

The researchers used a computer program to mix different pairs of face photos. (Credit: U. Oregon)

Zeithamova and Ashby used a computer program to mix different pairs of face photos. They created a library of new face images, some of which shared a “parent” face and therefore had subtle similarities in facial features.

Some faces that shared a parent face were given the same surname, while others were classified into different families. During a series of trials, participants learned the first and last name of each of the faces.

In a previous experiment, Zeithamova’s lab found that participants viewed faces as more similar when paired with the same last name. In this new work, she studied participants’ brain activity as they performed a similar task. This time, participants did not consciously rate faces from the same family as being more similar. But the prejudices still largely manifested themselves in their brains.

“We saw that brain representations became skewed to highlight commonalities between things that share a label,” says Zeithamova, with more similar patterns of activity when people saw faces in the same family.

When people saw face photos that shared a relative’s face but weren’t classified as related, brain activity was more distinct.

“We thought maybe a few regions would show this bias, but instead we found it everywhere,” she says.

When people have certain categories or concepts in mind, they focus on specific relevant features and ignore others. But to succeed in the task at hand here, the participants also had to pay attention to the differences between the faces; they had to be able to tell Peter Miller from Kyle Miller. Instead, the mere presence of category labels skewed the brain, and “people ignored the information they actually needed for the task,” says Zeithamova.

It remains to be seen to what extent the conclusion generalizes. Next, Zeithamova wants to determine whether pre-existing category labels also distort how the brain interprets new faces, and whether people can update categories in the face of new information.

Source: Laurel Hamers for University of Oregon

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