Psychology of Aging Psychology of Aging Definitions of Age Chronological age Chronological age is determined by the amount of time that has passed since birth (months or years). The most frequent method of determining age is to use chronological age. Biologically, functionally, mentally, and socially, age can all be described. Chronological age does not always accurately predict where a particular individual falls along each of these dimensions. Chronological age Biological age Biological age refers to a person's position concerning the number of years he or she will live (that is, their longevity). One person could live to be 70 years old chronologically, yet be 65 years old biologically. Another might live to the age of 90, so he or she would probably not be considered biologically old at the age of 65 because another 25 years of life remain. Because we cannot usually predict the exact length of a particular individual's life with great accurac...