same time there are enormous differences among 20-year-olds in intelli -
gence.
Over the course of the lifespan, we know pretty well what happens
to intelligence. Aside from a slow growth in knowledge (as shown byvocabulary test scores) and a progressive decline in reasoning and per -
ceptual ability , particularly late in life, there is rather little change. The
average 50-year-old is about as bright as the average 20-year-old, andthe above-average 50-year-old is almost certain to have been an above-average 20-year-old.
But this certainly does not mean that the mind is sunk in stagna -
tion for the greater part of life. Novelists use their intelligence to write
books, teachers to educate students, business executives to improvemanagement and expand sales. The work of a lifetime does not lead todevelopment of intelligence: Nobel Prize laureates would score no higher
on IQ tests after years of research than they would have in college. Butsurely their minds have not been wasted. Personality traits, we submit,are similar in their influence on adult life. Life does not lead to changeor growth in personality traits, but it allows a fascinating variety of situ-ations in which personal dispositions, for good or ill, play a part.
WHAT CHANGES?
Let us step back and review for a moment the changes that do occuracross the adult portion of the lifespan. Physically , aging brings with itchanges in mobility , sensory capacity , strength, and vigor. Certain cog -
nitive functions, particularly perceptual abilities and memory , show de -
clines, gradually at first, but at an increasing rate as we enter old age.
The world also changes as we age (with all the headaches that brings forresearchers, as we saw in Chapter 4). Our children grow up and moveout; our parents grow old and die. Nor are we simply passive victims ofthe crush of time: We make plans and decisions, change jobs and occa -
sionally spouses. Some of us often and all of us at times think our life is
stale and stagnant, but most of us are too busy living to worry about thefact that our personality is not developing.
Even leaving aside External Influences, we must certainly acknowl -
edge that there are extensive changes in a number of aspects of the per -
sonality system. Using FFT as a guide, we can briefly review these.
Chapter 8 considered the possibility of changes in Dynamic ProcessesInfluences of Personality on the Life Course 207