Sensory discrimination and intelligence: testing Spearman's other hypothesis

At the centenary of Spearman's seminal 1904 article, his general intelligence hypothesis remains one of the most influential in psychology. Less well known is the article's other hypothesis that there is "a correspondence between what may provisionally be called 'General Discrimination' and 'General Intelligence' which works out with great approximation to one or absoluteness" (Spearman, 1904, p. 284). Studies that do not find high correlations between psychometric intelligence and single sensory discrimination tests do not falsify this hypothesis. This study is the first directly to address Spearman's general intelligence-general sensory discrimination hypothesis. It attempts to replicate his findings with a similar sample of schoolchildren. In a well-fitting structural equation model of the data, general intelligence and general discrimination correlated .92. In a reanalysis of data published byActon and Schroeder (2001), general intelligence and general sensory ability correlated .68 in men and women. One hundred years after its conception, Spearman's other hypothesis achieves some confirmation. The association between general intelligence and general sensory ability remains to be replicated and explained.     

Size of the neocerebellar vermis is associated with cognition in healthy elderly men

Cerebellar volumes show small positive correlations with cognitive ability in young adults, but no studies have examined this relationship in older adults. Furthermore, no studies have examined relationships between sizes of subareas of the cerebellum and cognitive ability. We hypothesized that size of the two areas of the neocerebellar vermis would correlate with a battery of eight cognitive tests in 50 men aged 65-70. Size of the neocerebellar areas of the vermis correlated positively with several cognitive tests (r's=.29-.37, p<.05), whilst sizes of other parts of the vermis did not correlate with any cognitive tests. Total cerebellar volumes correlated significantly with a test of nonverbal reasoning (r=.030, p=.42). These findings suggest a specific association of neocerebellar vermis size with variations in cognitive ability in older adults.     

Reverse causation in activity-cognitive ability associations: the Lothian Birth Cohort 1936

Active lifestyles might protect cognitive abilities; however, studies rarely consider the reverse causal direction. Activity-cognition associations might reflect stable intelligence differences rather than a protective effect of activity. The Lothian Birth Cohort 1936 (n = 1091) completed cognitive tests aged 70, having taken an intelligence test aged 11. Activity (assessed by participation in 15 activities that produced a socio-intellectual activity factor, and by physical activity) was positively associated with cognition (r = .08 to .32, p ≤ .05). When age-11 IQ and adult social class were controlled, only physical activity remained significantly associated with general cognitive ability and processing speed.     

Do personality scale items function differently in people with high and low IQ?

Intelligence differences might contribute to true differences in personality traits. It is also possible that intelligence might contribute to differences in understanding and interpreting personality items. Previous studies have not distinguished clearly between these possibilities. Before it can be accepted that scale score differences actually reflect personality differences, personality items should show measurement invariance. The authors used item response theory to test measurement invariance in the five-factor model scales of the International Personality Item Pool (IPIP) and NEO-Five-Factor Inventory (NEO-FFI) across two groups of participants from the Lothian Birth Cohort 1936 with relatively low and high cognitive abilities. Each group consisted of 320 individuals, with equal numbers of men and women. The mean IQ difference of the groups was 21 points. It was found that the IPIP and NEO-FFI items were measurement invariant across all five scales, making it possible to conclude that any differences in IPIP and NEO-FFI scores between people with low and high cognitive abilities reflected personality trait differences.     

Vision and intelligence at age 83 in the Lothian Birth Cohort 1921

The extent to which visual function, measured as near and distant visual acuity and contrast sensitivity, is correlated with concurrently measured cognitive function and prior intellectual ability was investigated in a narrow age range group known as the Lothian Birth Cohort of 1921 (LBC1921). Participants were aged ~ 83 years at the time of testing (N = 321). A well-fitting structural equation model highlighted a significant contribution of a latent visual trait to a general fluid intelligence factor in old age, independent of the contribution from childhood intelligence. Additionally, childhood intelligence made a significant contribution to the general visual factor in old age. However, the model fitted equally well when the fluid intelligence factor is assumed to be a cause of the visual function latent trait, in which case childhood intelligence does not significantly influence vision in old age. We discuss these results with respect to four possible mechanisms by which vision and cognition can come to be correlated over the lifecourse.     

The association between cognitive ability across the lifespan and health literacy in old age: The Lothian Birth Cohort 1936

Three hundred and four participants in the Lothian Birth Cohort 1936 study took a validated IQ-type test at age 11 years and a battery of cognitive tests at age 70 years. Three tests of health literacy were completed at age 72 years; the Rapid Estimate of Adult Literacy in Medicine (REALM), the Test of Functional Health Literacy in Adults (S-TOFHLA), and the Newest Vital Sign (NVS). Participants who had a lower childhood IQ exhibited poorer performance on all three tests of health literacy taken in older adulthood. Relative cognitive change from age 11 to 70 and education were also important factors influencing performance on health literacy tasks, independent of childhood cognitive ability. It is important to understand the determinants of low health literacy in order to support individuals in managing their own health.     

Relationships between ability and personality:does intelligence contribute positively to personal and social adjustment?

Intelligence/personality associations were studied in four large datasets. Correlations between general ability (g) and major personality traits were generally consistent with previous findings. For other traits, an interpretation of the correlation patterning is that traits classifiable as adaptive in terms of personal and social adjustment have positive correlations with g, whilst maladaptive traits have negative correlations. Regression modelling confirmed these associations and structural equation modelling of selected traits showed that Neuroticism acts as a mediator of g on the outcome. Non-linear relationships between intelligence and personality were not found. In two of the datasets the correlation between Neuroticism and Psychoticism decreased with ability level, and the correlation between fluid and crystallised ability increased with level of Neuroticism.     

Social status,cognitive ability,and educational attainment as predictors of liberal social attitudes and political trust

We examined the prospective associations between family socio-economic background, childhood intelligence (g) at age 11, educational and occupational attainment, and social attitudes at age 33 in a large (N = 8804), representative sample of the British population born in 1958. Structural equation Modeling identified a latent trait of ‘liberal social attitudes’ underlying attitude factors that are antiracist, socially liberal, and in support of gender equality. Another attitude factor—‘political trust’—was relatively independent from the latent attitude trait and has somewhat different pathways in relation to the other variables included in the analysis. There was a direct association between higher g at age 11 and more liberal social attitudes and political trust at age 33. For both men and women the association between g and liberal social attitudes was partly mediated via educational qualifications, and to a much lesser extent via adult occupational attainment. For women the association between g and political trust was partly mediated through both educational qualification and occupational attainment, and for men it was mediated mainly via occupational attainment. Men and women who had higher educational qualifications and higher occupational status tend to be more socially liberal and more trusting of the democratic political system. In terms of socio-economic background, people from less privileged families showed less political trust, but did not differ much in liberal social attitudes from those born into relatively more privileged circumstances. This study shows that social background, cognitive ability, education, and own social status influence perceptions of society.