It seems somewhat illogical to assume the more physically attractive someone is the more intelligent they are, but that's exactly what we do - at least subconsciously - according to a new study.

Researchers in the UK report that their 124 participants rated more attractive faces as more intelligent, and suggest the so-called attractiveness halo effect says something about our inherent biases in judging other people.

"Previous studies have suggested there are valid facial cues that assist us in assessing someone's health or intelligence, but such cues are overshadowed by an 'attractiveness halo', whereby desirable attributions are preferentially ascribed to attractive people," said one of the team, Sean Talamas from the University of St Andrews.

Talamas collected the academic records and portrait photos of 100 university students before having them rated online by paid volunteers for perceived attractiveness, academic performance, conscientiousness, and intelligence.

The idea behind including academic performance and conscientiousness as categories was to allow for different ideas of what intelligence actually means, which can vary from person to person.

While there is no actual relationship between attractiveness and academic performance in the real world, there was "a strong positive correlation" between attractiveness and perceived intelligence, as well as perceived academic performance and perceived conscientiousness.

The researchers also found that when the attractiveness ratings were filtered out, perceived conscientiousness and actual academic performance were closely related. It would seem the better your academic performance, the more principled you appear to an onlooker, at least based on the 100-face sample involved here (which isn't exactly huge).

Talamas and his colleagues were also careful to filter out faces showing expressions, make-up, or jewellery to make sure the attention of the viewers was focussed solely on the face itself. All the photographs used in the experiment showed clean-shaven, Caucasian students to control for racial bias (and indeed bias for or against beards).

While this might seem like a rather inconsequential study, the authors note that perceived intelligence does have an impact on academic performance: if students are treated as clever by those around them, they're more likely to do well at school and college. With that in mind, the 'attractiveness halo' effect can have a serious impact.

"Facial impressions have consistently been shown to influence our opinions as well as bias decisions in politics, leadership, law, parental expectations and punishments on children, military rank promotion, and teacher evaluations," the researchers explain in their study, published in the journal PLOS One. "Clearly, the power of first impressions is critical and has repeatedly been shown to influence our opinions about a person."