***
The meaningfulness of trait psychology and the validity of trait mea -
sures are crucial to all the other arguments about aging and personality
we offer in later chapters, because the great majority of empirical stud -
ies of aging and personality employ these kinds of measures. In Chapter
8 we return to the theories of personality to consider alternative con -
ceptions of personality and its assessment. In the meantime we will as -
sume that we have provided adequate justification for looking seriously
at what happens to traits over the adult life course. We have argued thattraits are indispensable for laypeople and for psychological theorists;that there is growing agreement about how many important groups oftraits there are; and that there is encouraging evidence that several waysof measuring personality all lead to similar descriptions of people andthus are dependable bases for inferences about aging and personality .We can now turn to the data on aging. What effects do aging and the ac-cumulation of experience have on personality traits?Measuring Personality 57