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Signs

The distinguishing characteristics of old age are both physical and mental. The marks of old age are so unlike the marks of middle age that legal scholar Richard Posner suggests that, as an individual transitions into old age, that person can be thought of as different people "time-sharing" the same identity.

These marks do not occur at the same chronological age for everyone. Also, they occur at different rates and order for different people. Marks of old age can easily vary between people of the same chronological age.

A basic mark of old age that affects both body and mind is "slowness of behavior". The term describes a correlation between advancing age and slowness of reaction and physical and mental task performance. However, studies from Buffalo University and Northwestern University have shown that the elderly are a happier age group than their younger counterparts.