Toronto, June 23 (IANS): Our brain can quickly identify the gender of a person by looking at subtle variations in lip and skin colour, says a study.

"Contrast between the lips and skin is more pronounced in women than it is in men because their skin colour generally contains less red and therefore more green. This contrast is perceived by our brain as a female characteristic," said Nicolas Dupuis-Roy from University of Montreal in Canada.

The researchers came to this conclusion by asking 100 participants to guess the gender of 300 people after showing them different parts of their faces.

Researchers collected from internet 300 full-portrait photographs of Caucasian faces of both sexes. Some of the women wore make-up, while all the men were clean shaven. No other gender-identifying signs such as clothing or jewellery were visible.

Using the "bubbles" technique, the chromatic (colour) and achromatic (grey tones) content of the pictures was randomly sampled for 200 milliseconds, leaving only a portion of the visual information at a time.

This method allowed the researcher to know precisely which facial areas were most important for the task and when the information was extracted by the brain.

As the facial areas were displayed, the 100 observers were simply asked "Is this the face of a man or woman?"

Analysis showed that achromatic information in the eye and eyebrow area and chromatic information in the mouth area were most significant in recognising face gender.

Colour data for the mouth area was quickly isolated by the brain, barely 12 milliseconds after each face was presented, the release from University of Montreal said.