Men whose faces are more symmetrical - having matching left and right sides - are less prone to mental decline in old age, according to Edinburgh University psychologists.
They report in the journal Evolution and Human Behaviour that this may indicate fewer effects of diseases, toxins, malnutrition or harmful genetic mutations.
Says Dr Lars Penke: "Previous research has suggested that cognitive decline is an aspect of body-wide ageing. This link could show that facial symmetry can be used as a marker which could predict this decline."
Studies show that this it is not the case for women, possibly due to genetic differences or the fact that they live four years longer than men on average.
The report says that the beneficial effects of balanced features are particularly apparent between the ages of 79 and 83. The study used reasoning and reaction-time test scores amassed since 1932.
Previous research has already shown associations between facial symmetry and general health, as well as physical attractiveness.