"Don't judge a book by its cover" is just an old saying now -- scientists from the Czech Republic made a quite intriguing discovery that humans naturally have an inbuilt ability to predict a man's intelligence simply by looking at his face.

"The ability to accurately assess the intelligence of other persons finds its place in everyday social interaction and should have important evolutionary consequences," the research team said in the journal PLoS One.

The researchers used static facial photographs of 40 men and 40 women to test the correlation between measured IQ, perceived intelligence, and facial shape, and found out that both men and women were able to accurately evaluate the intelligence of men by viewing facial photographs.

In the study, they discovered that people tend to associate certain combination of facial traits with high intelligence. "Faces that are perceived as highly intelligent are rather prolonged with a broader distance between the eyes, a larger nose, a slight upturn to the corners of the mouth, and a sharper, pointing, less rounded chin," they said. "By contrast, the perception of lower intelligence is associated with broader, more rounded faces with eyes closer to each other, a shorter nose, declining corners of the mouth, and a rounded and massive chin."

"By contrast, we found no correlation between morphological traits and real intelligence measured with IQ test, either in men or women," they continued. "Two factors of general intelligence were significantly associated with perceived intelligence from men's faces: fluid intelligence and figural intelligence. Fluid intelligence is the capacity to logically solve problems independent of acquired knowledge. Figurative intelligence describes the ability to handle objects such as images, patterns and shapes."

However, the scientists also discovered that the ability to predict intelligence by looking at a face does not apply to women. "These results suggest that a perceiver can accurately gauge the real intelligence of men, but not women, by viewing their faces in photographs," they said. "However, this estimation is possibly not based on facial shape."

"Our study revealed no relation between intelligence and either attractiveness or face shape," they added. "People can accurately judge intelligence by looking at faces of men, but not women."

The research team claimed that the same result not being present when they used female faces could be due to the fact attractiveness clouds the judgment. "Another option is that women are pervasively judged according to their attractiveness," they said. "The strong halo effect of attractiveness may thus prevent an accurate assessment of the intelligence of women."