Abstract
Faces contain a wealth of information which is important for social functioning. Reports suggest that the ability to discriminate one face from another is significantly poorer in older, relative to younger, adults. We aimed to quantify changes in the profile of various aspects of face perception in healthy ageing. Synthetic face discrimination thresholds were measured using a memory-free "odd-one-out" task (Logan et al. 2016). Participants were healthy adults with corrected-to-normal vision (binocular LogMAR VA +0.1 or better). Five age groups (N=10) were tested: 20s (M=20.9±0.8 years), 50-59 (53.7±2.3), 60-69 (64.1±3.9), 70-79 (75.4±2.7) and 80-89 (84.2±3.1). Thresholds were measured for full-faces (upright and inverted), isolated external features (head-shape, hairline), internal features (eyes, nose, mouth, eyebrows) and circular-shapes (control task). Full-face discrimination thresholds increased monotonically as a function of age. Relative to 20-year-olds, thresholds were 1.03X (50-59), 1.10X (60-69), 1.29X (70-79) and 1.40X (80-89) higher in older adults. The effect of ageing in 50-90 year olds was well captured by a linear function: sensitivity declined, on average, by 11% per decade after 50 years. Testing isolated face information showed a similar monotonic decline, however, the slope depended on features: internal feature sensitivity decline was 3.31X and 3.94X steeper than for full-faces and external features respectively. In contrast, the inversion effect did not vary between age groups. Sensitivity to full-faces and component features showed a continuous decline with ageing. While ageing reduced sensitivity to all features under test, sensitivity to the internal features declined most rapidly. This age-related deficit cannot be explained by a general decline of visual or cognitive functioning as sensitivity to shapes was unaffected by aging. Further, equivalent inversion effects indicate that all participants employed the same holistic face processing strategies. Overall, these results suggest that ageing reduces sensitivity within the neural mechanisms which underlie face discrimination.
Meeting abstract presented at VSS 2017