First impressions of people — such as whether they are trustworthy, dominant or attractive — can develop from a glimpse as brief as 100 milliseconds or less. The team thinks their findings could help animators create more convincing characters, as well as aid those looking to make a good first impression through an application photo or social network profile picture, the BBC adds. Because first impressions can affect people's future behavior and can be difficult to overturn, "it's useful to know how we're being judged on our appearance, especially since these judgments might not be accurate — think of effects on court cases or democratic elections, for example," said study co-author Tom Hartley, a cognitive neuroscientist and psychologist at the University of York in England. The model found that mouth shape and area were linked to approachability — unsurprisingly, a smiling expression is a key component of an impression of approachability. The last is youthful-attractiveness — perhaps representing whether they would be a good romantic partner or rival." Given the increasing presence of faces on social media sites, first impressions could be more important than ever, Hartley suggested. To make the calculations, each of 1,000 face photos from the internet was shown to at least six different people, who gave it a score for 16 different social traits, like trustworthiness or intelligence. Media playback is unsupported on your device Media caption Cartoon faces based on the new mathematical model, sliding along 3 scales: approachability, dominance and attractiveness 
 
 By measuring the physical attributes of all 1,000 faces and putting them together with those scores, Dr Hartley and his team built a mathematical model of how the dimensions of a face produce those three impressions. The researchers then analyzed these faces using an artificial neural network, a kind of artificial intelligence computing system that mimics how the brain works. Another direction for research "will be to look at ways in which first impressions can be influenced by directly manipulating specific features, and whether, with the knowledge we now have, we can influence people's social decisions by choosing images with particular characteristics," he added. A computer model has found a smiling expression is key to a first impression of being approachable, while large eyes signal youthfulness, and dominance is linked partly to a masculine face shape.
– Have masculine or feminine features? A big smile? Characteristics like these, it seems, are central to our snap judgements of people's faces. Using a computer model, researchers have figured out how different features affect our first impressions, the BBC reports. The system is based on 1,000 pictures of different faces gathered online. In a study, researchers had respondents give opinions of these faces, focusing on approachability, dominance, and attractiveness. Researchers then created a mathematical model that translated those opinions into distinct facial measurements—an effort to "crack the code of first impressions," notes Smithsonian. The result was a computer program that generates cartoon faces intended to be dominant or submissive, approachable or off-putting. Another batch of study subjects offered their opinions of the cartoons—and they fit the computer's assessments. Masculine features and a good tan were apparently tied to the perception of dominance, while smiles were associated with approachability, LiveScience reports. Knowing how first impressions work may be particularly important these days: "Whereas in the past, we got to know people through meeting them in the flesh, increasingly, our first contact is online, and our first impressions are based on the images we provide on social media profiles," says the study's lead author. Of course, what's attractive could change a lot in the next century.