Face photos makes it possible to distinguish between different identities. For a study, researchers sought to measure the effects of aging on several face identity discriminating factors. A memory-free “odd-one-out” test was used to evaluate the sensitivity of face discrimination. 20–49, 60–69, 70–79, and 80–89 years old healthy people with normal eyesight (N = 15) were tested. 

Sensitivity was evaluated for photographs of the entire face (all features visible), exterior characteristics like the head shape and hairline, interior features like the nose, lips, eyes, and brows, as well as closed-contour forms (control object). After age 50, the sensitivity to complete faces gradually decreased by around 13% every decade. The age impact on face discrimination sensitivity persisted after controlling for age-related variations in visual acuity. Age also led to a decrease in facial feature sensitivity. Although the effect for exterior features was comparable to full-faces, the rate of reduction for internal, as opposed to external, features was noticeably higher (about 3.7 times). 

Age had no impact on form sensitivity, on the other hand. The general pattern of sensitivity to various forms of facial information was the same across all age groups. Although encoding of internal characteristics was significantly decreased, healthy aging was related to a persistent loss in sensitivity to both full faces and face features. There were no variations in low-level vision to explain this age-related loss. Age-related changes in sensitivity to forms were unaffected, indicating that general cognitive decline or lower-level visual deficiencies cannot account for the findings. Instead, a particular reduction in the systems underlying face discrimination was linked to healthy aging.

Reference: jov.arvojournals.org/article.aspx?articleid=2783526