Sensitivity to horizontal and vertical spatial relations in younger and older adults' face perception

As many visual functions, also face perception is subject to age-related decline. Here we addressed whether sensitivity to 2nd order spatial relations among facial features suffers from aging. Thirty-one younger (M = 23.5 years) and fifty-seven older adults (M = 61.7 years) performed a change detection task in same/different format with faces manipulated in eye distance (horizontal, H) and eye height (vertical, V), while the face stimuli were composed of different sets of internal features (eyes, nose and mouth), shown in isolation or with the embedding external feature context (face outline with ears, hairline and hairs). V relations showed much stronger age-related decrease than H relations. In both age groups, sensitivity to H changes was practically unaffected by presence or absence of internal features and improved modestly from external feature context. Sensitivity to V changes was differently modulated by internal and external features in both age groups. Younger adults showed cumulative improvement from additional facial cues, while older adults performed worse with isolated sets of internal features and relied solely on external features when they were available. Both age groups showed similar effects of face inversion, which were of medium size in H but strong in V. Serious impairment in vertical 2nd order relations and internal feature weakness, coupled with reliance on just external features, indicate age-related impairment of internal feature coding and a loss of spatial cue integration. However, intact inversion effects suggest that also the elderly process faces using category-specific modules.