The vast majority of people can compare a man and woman or a parent and baby and see when two people of different age or sex are genetically related, despite not knowing they are part of the same family, but not much has been known about how we compute this process until now.
A recent study published in the Journal of Vision broadens the understanding of the brain"s ability to see through these underlying variations in facial structure, claims Dr Harry Griffin, from the Department of Cognitive, Perceptual and Brain Sciences at University College London.
"Being able to see the family resemblance between faces that have some underlying difference, such as the difference between male and female faces, is an ability that is not well understood and merits further investigation to work out how visual information about faces is organised," he explained.
In the study, researchers conducted two experiments using original and synthesized cross-gender "sibling" faces that resemble each other and "anti-sibling" faces that have the opposite characteristics of the original face.
During the first experiment, participants were asked to identify male-female sibling pairs and chose the sibling pair significantly more often than the randomly selected cross-gender pairings and the random pairings more often than the anti-face pairings.
Dr Griffin said this pattern of results shows that, when people see a face, they compare it to an average face for that gender, allowing them to pick out only the face cues that tell them about family membership while disregarding the irrelevant gender cues.
During the second experiment, with the use of the visual adaptation method of biasing an observer"s perception of objects through prolonged exposure, participants were shown a male anti-sibling generated from a female face.
The results showed that adapting to the male face influenced the perceived identity of a subsequent identity-ambiguous female face, which the researchers believe implies that the cues underlying family resemblance for both male and female faces are processed within the same brain space.
Dr Griffin said the team used the method to show that the facial appearance of men and women are processed by overlapping populations of brain cells.
"This takes our understanding beyond the conceptual and gives a picture of how the brain actually works," he explained.
The specialist said the team hopes the findings will prompt other researchers to investigate the perception of similarity in other aspects of facial appearance, such as underlying differences in age or racial groups, and also suggest that the results may have a far-reaching impact on the computer science industry.
Commenting on the study, computer scientist and team member Peter McOwan, from Queen Mary, University of London, said that understanding how people encode faces can inform computer scientists who are building face recognition systems for security applications.
It could also benefit computer graphics teams building synthetic faces for applications in the film and gaming industry and to enhance human computer interaction, the expert noted.
by Adrian Galbreth