Our decisions to trust people with our money are based more on how they look then how they behave, according to new research from the University of Warwick.

In a paper recently published in the PLoS One journal, researchers from Warwick Business School, the University College London and Dartmouth College, USA, carried out a series of experiments to see if people made decisions to trust others based on their faces.

They found people are more likely to invest money in someone whose face is generally perceived as trustworthy, even when they are given negative information about this person's reputation.

The team used a computer algorithm to create a set of 20 pairs of faces at opposing ends of the trustworthiness scale. This computer software modifies the apparent trustworthiness of faces by altering their features. The researchers were able to experimentally manipulate the unfakeable features (those related to shape of the face) that make a face look trustworthy or untrustworthy. These 40 faces were then used in a series of trust games with human participants.

Each volunteer was given a sum of money and told they could invest any part of the amount in a trustee whose face appeared on the screen. Any amount they invested would be tripled and volunteers were told it was then up to the trustee to decide how much to send back to them. Thus participants had an incentive to invest only in trustees who could be expected to return more than the invested amount.

The researchers found that 13 out of 15 participants invested more, on average, in the trustworthy identities. In a second experiment, the researchers gave the volunteers information about whether the trustees had good or bad histories. Even with this inside information, the average amount invested in those who looked 'trustworthy' was 6% higher.

Dr Chris Olivola from the University of Warwick's Warwick Business School said: "Trustees with good and bad histories benefitted equally from trustworthy-looking facial features. The temptation to judge strangers by their faces is hard to resist. Trustworthiness is one of the most important traits for social and economic interactions and our study examines whether people take potentially costly actions in line with their face-based trustworthiness judgments.

"It seems we are still willing to go with our own instincts about whether we think someone looks like we can trust them."