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Gaetano, JM 2015, 'The stimulus invariance of human sex cue processing: a cross-cultural study using non-face stimuli', PhD thesis, Southern Cross University, Lismore, NSW.

Copyright JM Gaetano 2015


Socially valuable pieces of information, such as a new colleague’s name, are generally learned by asking; others, such as whether the newcomer is female or male, can be perceived without question. Face and body structure, tone of voice, and even invisible and inaudible sweat compounds are but some of the biological indicators potentially at the observer’s disposal when deducing another’s sex. Perhaps because of the automaticity and redundancy associated with sex perception, the question of how this ability works in a general sense has only rarely been scrutinised, if at all. The majority of sex perception studies focus on categorisation performance in response to female and male faces specifically, thus it is unknown to what extent outcomes generalise to the perception of other sexual dimorphisms. The following body of research is concerned with understanding this taken-for-granted ability more broadly. To that end, visual stimuli comprising representations of human hands were deployed. The specific aim of this thesis was to determine whether observers of ambiguous or unfamiliar, female and male hands are subject to the same sex perception phenomena associated with similarly manipulated faces.

The wider, person perception literature surveyed in Chapter 2 suggests a priori that sex perception is not strictly governed by stimulus-specific mechanisms, and experimental data described across subsequent chapters effectively support that notion. Chapter 4 provides primary evidence that human hands – like faces – can be used to indicate an individual’s sex, even if colour and texture cues are removed and the remaining cues are presented only briefly. Those initial data also showed that when hand cues are sufficiently ambiguous, observers tend to classify them as male more often than female – an effect shown to arise not from sensitivity differences but from differences in response criteria. Specifically, Chapter 4 demonstrates for the first time that male bias arises via a dual-target mechanism: observers are conservative in their judgements of targets as female, and also liberal in their judgements of targets as male. This novel finding extends on what was previously known about male bias, which hitherto had been documented in studies utilising face and body-motion stimuli. Thus, data from Chapter 4 justifies further the testing of the common mechanisms hypothesis across subsequent chapters.

The role of familiarity between observer and stimulus was explored in Chapters 5 and 6. Chapter 5 described the sensitivity with which Caucasian and Asian observers are able to discriminate sex from either same-raced or other-raced hands, which represented either more or less familiar presentations, respectively. Chiefly, those experiments showed that the own-race advantage observed previously in relation to faces also applies to hands. Interestingly, the sensitivity rates of Asian observers, but not Caucasian observers, changed relative to how many fe/males there were in a set, suggesting different perceptual learning strategies across cultures. In Chapter 6, the analytic focus migrated from sensitivity to bias outcomes; it was shown there that male bias per se is not specific to Western observers, nor is it dependent absolutely on the observer’s familiarity with certain race cues. More specifically, it seems that the symmetry of the dual-target mechanism observed in Chapter 4 breaks down when cue familiarity is a variable: that is, female criteria are strict and male criteria are lenient under certain conditions for own-race observers, but for other-race observers only the male criteria are shifted.

Finally, data from two pilot experiments in Chapter 6 yield convergent evidence of the ubiquity and perceptual nature of male bias: the effect is found to persist in response to novel silhouette face profiles, and even across trials in which observers are asked to categorise something other than sex. In the seventh and final chapter, present results are collated to infer an explanatory model of cue-based sex perception. It is concluded that the ability to categorise others as female or male is partially subserved via pan-stimulus mechanisms in nature.