Stability of intelligence: A 40-year follow-up.

Abstract

The Revised Examination "M," a measure of intelligence, was readministered to 260 men approximately 40 years after they had received this test as World War II army recruits. Their average age and educational level was 64.7 years and Grade 8.7, respectively. Three sets of scores were compared: those obtained at the time of army enlistment; current scores obtained within the regular time limits of the test; and current scores obtained within double the test's regular time limits. The results indicated a reliable but minor decline in total score in the regular speeded condition and a reliable improvement over wartime total scores in the double-time condition. Slower performance did not account for the decline observed on the nonverbal cognitive tasks, particularly spatial problem-solving, but was associated with the decrements recorded for mathematical and verbal reasoning skills. Significant gains in score were observed on the measures of vocabulary and mechanical knowledge in the speeded condition, with further gains noted in the double-time extension. Test-retest correlation coefficients, in general, attested to the long-term stability of individual differences among members of the sample, irrespective of the direction of cognitive performance changes. Gains in the doubletime extension were associated with educational status but not with current age. Both age and educational level, in addition to early adult intellectual status, predicted current intellectual functioning. Finally, self-reported current activity level, as an indicator of personal lifestyle, was related both to early and to late adult intellectual ability.

The stability of general intelligence from early adulthood to middle-age

“…It is beyond the scope of this article to present a thorough review of the extensive longitudinal research that followed, so it will have to suffice to mention that several more recent studies have confirmed that individual differences in measures of mental ability are relatively stable in adulthood (Arbuckle, Maag, Pushkar, & Chaikelson, 1998;Deary, Whalley, Lemmon, Crawford, & Starr, 2000;Eichorn, Hunt, & Honzik, 1981;Hertzog & Schaie, 1986;Plassmann et al, 1995;Schwartzman, Gold, Andres, Arbuckle, & Chaikelson, 1987).…”

Age and Individual Productivity: A Literature Survey

“…The second group, fluid abilities, concern the performance and speed of solving tasks related to new material, and include perceptual speed and reasoning abilities. Schwartzman et al (1987) find that verbal skills (crystallised abilities) remain virtually unchanged, while reasoning and speed (fluid abilities) decline with age, based on psychometric test results of men in different age groups. In a test-retest study of twins, Blum et al (1970) provide similar findings: Vocabulary size is observed to remain constant from young to old ages, despite a general reduction in other cognitive abilities.…”

The betula prospective cohort study: Memory, health, and aging

“…With the exception of intelligence (e.g., Schaie, 1983;Schwartzman, Gold. Andres, Arbuckle, & Chaikelson, 1987), relatively little longitudinal research on cognitive development in adulthood has been conducted.…”