Hands are a useful sex cue

Hands, in all their delightful forms, are useful for detecting the sex of a person even when the view of the hand is degraded, according to research from Southern Cross University.

Psychology PhD student, Justin Gaetano, from the School of Health and Human Sciences, conducted two experiments to measure sex discriminations and sex categorisations, which are high-value social behaviours. He recently had an article published in journal PLoS ONE titled ‘Hands as Sex Cues: Sensitivity Measures, Male Bias Measures, and Implications for Sex Perception Mechanisms’.

“These sex discriminations and categorisations are high value social behaviours which mediate almost all inter-personal interactions,” he said.

“We found hands are a useful sex cue. Interestingly though, we also found that there was a male bias when those in the study had to identify a hand in a digital picture that had been stripped of colour and texture. That is, observers had a tendency to report the presence of males under ambiguous viewing conditions.

“In other words, observers apply a conservative criterion when judging cues as signalling female, and a liberal criterion when judging cues as signalling male.”

Mr Gaetano’s findings were from two experiments involving 12 experienced psychophysical observers (six female and six male), looking at digital photographs of the dorsal and palmar surfaces of 15 female and 15 male hands.

“The photographs were digitally manipulated for size and in some cases had colour and texture removed so that only the silhouette of the hand was shown. Also, the photographs were shown at different speeds,” Mr Gaetano said.

“What we found in the first experiment was that sex discrimination accuracy is mediated by colour and texture cues and by the duration the photograph was shown to the respondent. So, when the cues were more ambiguous, performance on the sex discrimination task varied between female and male hands with sex misclassification rates higher for female and lower for male hands.”

The second experiment was to explore why the observers reported seeing male hands when the cues that are normally sexually identifiable were ambiguous.

“In this experiment the same observers completed two signal detection tasks. In one, observers discriminated silhouette hands as female or not. In the other, observers discriminated silhouette hands as male or not,” Mr Gaetano said.

“That technique makes it possible to discriminate whether the male bias manifests as the result of a difference in sensitivity to cues that signal female and male hands, or from an observer bias.”

What does his study say about human behaviour?

“Without necessarily realising it, we make sense of our social world by constantly processing information about others, like hair length, eye colour, perfume type, clothing style, and so on,” Mr Gaetano said.

“What we have shown here is that humans can very quickly determine whether someone is female or male, from mere glances of that person’s hand. Surprisingly, such snap decisions are often correct, but if the observer is in doubt, they are more likely to say the hand is male. The rule seems to be ‘if senses fail, better say male’.

“More intriguingly, this male bias can be invoked by other ambiguous cues as well – face shape, human gait, and even non-visual cues like voices can produce the bias. From an evolutionary perspective, it could be less risky to assume an ambiguous other is male. For instance, if you are walking down a dark alley and hear footsteps approach from behind, the quick decision that the lurker is male might better prepare you for a fight-or-flight situation.”

Photo: Justin Gaetano.