That instant feeling that somebody looks trustworthy may have less to do with their face than we think, with new research from the University of Aberdeen showing our judgement can be influenced by the person we looked at moments earlier.

The study is the first to demonstrate systematically that impressions of trustworthiness can shift according to the sequence of faces we see, with potential implications for dating apps, social media and even eyewitness identification.

Researchers from the University of Aberdeen and Curtin University in Australia examined whether our first impression of a face is determined entirely by the person in front of us or subtly altered by faces we have recently seen.

Their findings suggest the answer can depend on something as simple as how quickly faces appear, how close together they are and how similar the people look.

When similar faces were viewed quickly or appeared close together, people’s judgement of the second person’s trustworthiness tended to be pulled towards their impression of the first.

Researchers describe this as an attractive bias, where perceptions of two faces become more similar than they would have been if each had been viewed independently.

But extending the time spent looking at the first face, increasing the distance between the images or showing two people who looked very different could produce the opposite effect.

In those circumstances, perceptions of the second person’s trustworthiness were pushed away from the judgement made about the first face.

The findings could be particularly relevant to the way people use dating apps and social media, where large numbers of faces can be viewed in rapid succession.

There could also be more serious implications for situations such as eyewitness identification, where judgements about one face could potentially influence perceptions of the next.

Lead researcher Dr Fiammetta Marini said:

“Judging trustworthiness is fundamental to daily life, influencing economic decisions, job interviews and even legal sentences.

“The goal of our study was to map the conditions that determine whether a previous visual experience will push us to ‘attract’ or ‘repel’ the judgement of trustworthiness of a new face towards or away from the previously seen face.

“This study is the first to systematically dissociate these effects, providing a basis for understanding how our social interactions are shaped by recent visual experience.

“We demonstrated that simple factors, such as how long we look at a face, where two successive faces are seen, or how similar they look, determine how the previous face will influence the trustworthy appearance of the following one.

“Traditionally, research has considered trustworthiness impressions as stable over time and solely dependent on the single face we are looking at.

“Here, we show that our impressions can be affected by what was seen in the past.

“Also, while studies on similar attractive or repulsive effects exist for simple visual characteristics (such as the orientation of a line), this is the first research to systematically demonstrate that the same principles govern complex social judgments such as perceived trustworthiness.”

Dr Mauro Manassi added:

“We like to think we can instantly tell whether someone seems trustworthy, but our research suggests those first impressions are surprisingly easy to bias.

“Perhaps it’s a reminder that first impressions are not always as objective as they feel, and that trust really does take time.”