It is usually fairly easy to infer the sex, relative age, or ethnic background from the face of another person, even if we have never seen the person before. What aspects of faces carry these visually derivable characteristics? How is the brain able to extract these signals from the visual input? What are the cognitive and neural processes involved in these seemingly effortless tasks?
In a number of studies using behavioral measures, event-related brain potentials, and functional MRI, we observed that none of these characteristics is carried by a single facial feature. Instead, they are more likely represented in the configuration or the “Gestalt” of the faces. Interestingly, both the degree of automaticity and the specific processing stage at which a specific characteristic is extracted differ. For instance, age seems to be more automatically processed than sex, and both age and ethnicity seem to be processed within 170 ms after stimulus onset (i.e., in the N170 ERP component), whereas sex is processed at a later stage. Importantly, the various visually-derivable characteristics interact, and our current work is taking this into account.
The figure below shows “average” faces created from 32 individual older male, young male, older female, and young female adult faces respectively. Changes in face shape are clearly visible, but age-related changes in texture are not well represented, which is a result of the averaging technique.
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