When we first meet another person, we typically form an initial impression of them based on their facial features and appearance. These first impressions of others could potentially influence our subsequent cognitive processes, such as what mental states we believe that the people we meet are experiencing at a given time.

Researchers at the University of California San Diego (UCSD), the California Institute of Technology and Dartmouth College carried out a study investigating the potential relationship between first impressions of faces and the inference of mental states. their findings, published in Nature Human Behaviorsuggest that first impressions of faces influence the inference of other people’s mental states.

“Over the years there have been a lot of surprising findings showing how first impressions from faces can predict important outcomes, such as which candidates would win an election, which politicians would be convicted of corruption, and which offenders would be sentenced to death,” Chujun Lin, first author of the paper, told Medical Xpress.

“These findings show that the snap judgments people make about others based merely on their faces may bias consequential decision-making in the real world, ranging from who we vote for, who law enforcement investigate and how juries evaluate cases.”

As most people rarely engage in criminal investigations or legal trials, their initial impressions of others based on appearance might not necessarily have a crucial impact on their decisions. Lin and her colleagues set out to determine whether first impressions also influence real-world scenarios that people engage in on a more regular basis.

“We investigated how first impressions may shape the way people infer each other’s moment-to-moment thoughts and feelings,” said Lin. “Understanding how each other feels and thinks is a crucial task in daily life as long as you engage with other people.”

A key challenge associated with psychology research is to conduct reproducible studies that yield similar results across different samples of participants, even in somewhat different settings. Lin and her colleagues thus tried to devise reproducible and robust experimental methods that could be employed by other researchers.

“To understand the complex relationships between face perception, mental state judgment, trait judgment, and situational effect, we used computational models to quantitatively select a large number of faces, mental state terms, trait terms, and situation descriptions that are representative of those people encounter in everyday life,” explained Lin.

“We asked participants to view faces and infer how much those individuals would feel certain mental states in given situations.”

The researchers also asked a separate group of participants to look at the same images of faces and infer the traits of the people they belonged to. Using the information they gathered, they then digitally manipulated the traits of faces.

“We quantified to which degree changing the perceived traits of a face would change people’s expectations of how this individual may feel and think in different situations,” said Lin. “To make sure that our results can be applied to a wide range of populations, our data and models were based on participants from five continents: Africa, Asia, Europe, North America, and South America.”

Lin and her colleagues closely examined how their study participants thought specific people in images would feel 60 different mental states in 60 real-world scenarios.

For example, how much they thought a specific person would feel jealous when hearing that their best friend was admiring a new person or the extent to which they would feel lonely if they felt like a minority or different from everyone else in a group.

“We found that 47 of these 60 mental state inferences were shaped by how the individual looks (eg, if you look feminine, people would expect that you feel more jealous when hearing (of a) best friend admiring a new friend; if you look like a leader, people would expect that you feel less lonely when being different from everyone else in a group),” said Lin.

“This means that in most circumstances, when other people are trying to understand how you feel and think, their understanding will be biased by their first impressions of your personality (which is not necessarily your true personality but just others’ judgments).”

Interestingly, the researchers found that first impressions shaped mental state inferences across participants living in all five continents on Earth. This suggests that their findings are robust and the effect they observed is relevant to all people, irrespective of their nationality or cultural background.

“The goal of scientific research is to improve human life, thus it is important for the way that psychologists conduct research to be relevant to real life,” said Lin.

“This may seem straightforward, but this is not the case in our field. Most research was conducted using highly controlled designs, such as having participants read vignettes and press buttons. But experiment designs that bear little resemblance to the real world are unlikely to reveal psychological processes in the real world.”

The recent study by Lin and her colleagues could inform future research efforts focusing on how first impressions influence what humans think about others and interpret their behavior or emotions. A key objective of her lab at UCSD, the IMPRESSION IN ACTION LABis to continue gathering more naturalistic knowledge of how people understand each other in the real world.

“We do so by promoting more naturalistic experiment designs (such as viewing videos and telling stories), leveraging more advanced computational tools that are proven to work in the complex real world (such as large language models and vision models), and examining more diverse populations (participants across world regions),” added Lin.

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