Man or woman? Age affects sex perception

While the human brain takes a fraction of a second to categorise a face as male or female based on cues like a chiselled jawline it seems the brain also takes into account another factor when determining gender—the age of a face.

A UWA-led study suggests we are quick to label young girls as female and older men as male, while older women and younger men take our brains longer to work out.

UWA cognitive neuroscientist Nadine Kloth showed photographs of young, middle-aged and old faces to the study participants and asked them to make a decision on the face's gender.

"As the female faces got older, participants took increasingly longer times to make that correct sex judgement," she says.

"For the male faces we found the complete opposite…the older they were, the faster the participants were able to say 'ok, that's a male'."

People were also more likely to be correct when they were picking the sex of young female faces and old males faces than young male faces and old female faces.

The study is the first to show that age affects our perception of a face's gender differently depending on whether that face belongs to a man or a woman.

Eliminating skin texture blurs classification ability

Dr Kloth says the next stage of the research was to present participants with photos of faces that were blurred to artificially smoothen the skin texture.

Compared to unblurred pictures, the young and middle-aged female faces took the same amount of time to classify and the classification of older female faces actually sped up.

The opposite was true for men, with the blurred photos slowing down the time it took to classify middle-aged and older men as male.

The work suggests that eliminating skin texture—a cue indicative of masculinity—made it harder to classify these older male faces.

Dr Kloth says working on this project made her realise the desired effects of make-up are closely related to the findings of the study.

For instance, women often tend to artificially enhance the distance between their eyelid and brow by plucking their eyebrows and highlighting the brow bone, which likely enhances the face's perceived femininity.

Similarly, using foundation and powder—thereby smoothing the skin texture—might make women look not only younger but also more feminine.

"I just thought it was quite intriguing looking at it from a scientific perspective," Dr Kloth says.