125 years of intelligence in the American Journal of Psychology

A survey is made of intelligence research in the 125 years of The American Journal of Psychology. There are some major articles of note on intelligence, especially Spearman's (1904a) article that discovered general cognitive ability (g). There are some themes within intelligence on which articles appeared over the years, such as processing speed, age, and group differences. Intelligence has not been a major theme of the journal, nor has a differential approach to psychology more generally. There are periods of time--especially the 1970s--during which almost no articles appeared on intelligence. The key articles and themes on intelligence differences are discussed in detail.     

On Intelligence IV: Toward a restoration of general intelligence

The present paper points to the limitations of a focusing on narrow primary factors of intelligence and argues for broad-factor structuring of ability data. Recent studies of such broad attributes would suggest a "rapprochement" between Spearman's general intelligence model and Cattell's theory of Fluid and Crystallized Intelligence. Discussing the neo-Spearman organization of abilities thus proposed, the paper argues, however, that the conceptualization of intelligence suggested by this structural model is more akin to Thomson's "sampling" model than to the "power" model of both Spearman and Cattell. The possible role of these interpretations of ability data in future research on intelligent behavior is discussed.     

Introduction to the special section on cognitive abilities: 100 years after Spearman's (1904) "'General intelligence,' objectively determined and measured"

The study of individual differences in cognitive abilities is one of the few branches of psychological science to amass a coherent body of empirical knowledge withstanding the test of time. There is wide consensus that cognitive abilities are organized hierarchically, and C. Spearman's (1904) general intelligence occupies the vertex of this hierarchy. In addition, specific abilities beyond general intelligence refine longitudinal forecasts of important social phenomena and paint a rich portrait of this important domain of psychological diversity. This opening article identifies and then reviews 5 major areas concerning the personological significance of cognitive abilities and the methods used to study them. In models of human behavior and important life outcomes, cognitive abilities are critical in more ways than social scientists realize.     

Goal neglect and Spearman's g: competing parts of a complex task

In goal neglect, a person ignores some task requirement though being able to describe it. Goal neglect is closely related to general intelligence or C. Spearman's (1904) g (J. Duncan, H. Emslie, P. Williams, R. Johnson, & C. Freer, 1996). The authors tested the role of task complexity in neglect and the hypothesis that different task components in some sense compete for attention. In contrast to many kinds of attentional limits, increasing the real-time demands of one task component does not promote neglect of another. Neither does neglect depend on preparation for different possible events in a block of trials. Instead, the key factor is complexity in the whole body of knowledge specified in task instructions. The authors suggest that as novel activity is constructed, relevant facts, rules, and requirements must be organized into a "task model." As this model increases in complexity, different task components compete for representation, and vulnerable components may be lost. Construction of effective task models is closely linked to g.     

Visual information processing and intelligence

Measures of inspection time (IT) have robust, moderately-sized correlations with IQ-type test scores. However, the reason for the IT-IQ correlation is not understood. Although the original theory asserted that IT performance was based on a single parameter—essentially speed of visual processing—peculiarities of the task have afforded other interpretations of IT differences and the IT-IQ association. In the present report two new visual processing tasks, visual change detection (VCD) and visual movement detection (VMD) are found to be correlated at or above .4 with IT and with non-verbal scores from the Alice Heim 4 test of general intelligence. VCD and VMD, in common with IT, assess the stimulus duration that is required by subjects in order to make an accurate discrimination. VCD and VMD, however, require a broader attentional focus than IT and do not involve backward masking. Measures of contrast sensitivity, a difficult discrimination task in which stimuli are not time-limited, had near-to-zero correlations with other visual processing tasks and with IQ-type test scores. We tested the hypothesis that only the latent trait derived from the speeded visual processing tasks (rather than task-specific features) would correlate with cognitive ability, and this was supported. The present study adds weight to the view that it is the ability to make accurate discriminations in the face of limited stimulus time that causes IT to correlate with psychometric intelligence. The psychological correlates of VCD, in terms of neural circuits that detect “difference” suggest a new line of investigation into the psychobiological bases of human intelligence.     

Sensory Discrimination,Working Memory and Intelligence in 9‐Year‐Old and 11‐Year‐Old Children

More than a century ago, Galton and Spearman suggested that there was a functional relationship between sensory discrimination ability and intelligence. Studies have since been able to confirm a close relationship between general discrimination ability (GDA) and IQ. The aim of the present study was to assess whether this strong relationship between GDA and IQ could be due to working memory (WM) demands of GDA tasks. A sample of 140 children (seventy 9‐year‐olds and seventy 11‐year‐olds) was studied. Results showed that there was a significant overlap between WM, GDA and fluid intelligence. Furthermore, results also revealed that WM could not explain the relationship between GDA and fluid intelligence as such, but that it acted as a bottleneck of information processing, limiting the influence of GDA on the prediction of fluid intelligence. Specifically, GDA's influence on the prediction of intelligence was only visible when WM capacity was above a certain level. Copyright © 2013 John Wiley & Sons, Ltd.     

General mental ability in the world of work: occupational attainment and job performance

The psychological construct of general mental ability (GMA), introduced by C. Spearman (1904) nearly 100 years ago, has enjoyed a resurgence of interest and attention in recent decades. This article presents the research evidence that GMA predicts both occupational level attained and performance within one's chosen occupation and does so better than any other ability, trait, or disposition and better than job experience. The sizes of these relationships with GMA are also larger than most found in psychological research. Evidence is presented that weighted combinations of specific aptitudes tailored to individual jobs do not predict job performance better than GMA alone, disconfirming specific aptitude theory. A theory of job performance is described that explicates the central role of GMA in the world of work. These findings support Spearman's proposition that GMA is of critical importance in human affairs.     

Temporal information processing and pitch discrimination as predictors of general intelligence.

In the present study, the relationship between performance on temporal and pitch discrimination and psychometric intelligence was investigated in a sample of 164 participants by means of an experimental dissociation paradigm. Performance on both temporal and pitch discrimination was substantially related to psychometric intelligence (r=.43 and r =.39). Regression analysis and structural equation modeling suggested that both psychophysical domains can be considered as valid predictors of psychometric intelligence. Both predictor variables contributed substantial portions of both shared and unique variance to the prediction of individual differences in psychometric intelligence. Thus, the present study yielded further evidence for a functional relationship between psychometric intelligence and temporal as well as pitch discrimination acuity. Eventually, findings are consistent with the notion that temporal discrimination - in addition to general aspects of sensory discrimination shared with pitch discrimination reflects specific intelligence-related aspects of neural information processing.     

Adjustments to the correction for attenuation

With respect to the often-present covariance between error terms of correlated variables, D. W. Zimmerman and R. H. Williams's (1977) adjusted correction for attenuation estimates the strength of the pairwise correlation between true scores without assuming independence of error scores. This article focuses on the derivation and analysis of formulas that perform the same function for partial and part correlation coefficients. Values produced by these formulas lie closer to the actual true-score coefficient than do the observed-score coefficients or those obtained by using C. Spearman's (1904) correction for attenuation. The new versions of the formulas thus allow analysts to use hypothetical values for error-score correlations to estimate values for the partial and part correlations between true scores while disregarding the independence-of-errors assumption.     

Working memory and intelligence--their correlation and their relation: comment on Ackerman, Beier, and Boyle (2005)

On the basis of a meta-analysis of pairwise correlations between working memory tasks and cognitive ability measures, P. L. Ackerman, M. E. Beier, and M. O. Boyle (2005; see record 2004-22408-002) claimed that working memory capacity (WMC) shares less than 25% of its variance with general intelligence (g) and with reasoning ability. In this comment, the authors argue that this is an underestimation because of several methodological shortcomings and biases. A reanalysis of the data reported in Ackerman et al. using the correct statistical procedures demonstrates that g and WMC are very highly correlated. On a conceptual level, the authors point out that WMC should be regarded as an explanatory construct for intellectual abilities. Theories of working memory do not claim that WMC is isomorphic with intelligence factors but that it is a very strong predictor of reasoning ability and also predicts general fluid intelligence and g.     

Secular declines in Spearman's g: some evidence from the United States

The Flynn Effect (J. Flynn, 1987) refers to the apparent increases in intelligence quotient (IQ) observed over the past few decades. A related phenomenon is that the variance in test scores accounted for by Spearman's g (C. Spearman, 1904) varies according to IQ level. That is, g accounts for less variance in high IQ groups than in low IQ groups. Spearman termed this variant aspect of g the "law of diminishing returns." This study extends prior research on the Flynn Effect and the law of diminishing returns by examining changes in the statistical importance of Spearman's g that may accompany secular increases in IQ. Based on the standardization data from the United States versions of the Wechsler scales (i.e., Wechsler Preschool and Primary Scales of Intelligence, D. Wechsler, 1967; Wechsler Intelligence Scale for Children, D. Wechsler, 1949; Wechsler Adult Intelligence Scale, D. Wechsler, 1955), this study indicated that, in most cases, the statistical significance of Spearman's g has indeed declined over the past several years. A. R. Jensen (1998) suggested that the components of the Flynn Effect warrant special investigation. The present study addresses this issue, in part by analyzing the Verbal and Performance subscales of the Wechsler scales. Additionally, this study further confirms the law of diminishing returns as applicable to different ages and time periods.     

Inspection time and the relationship among elementary cognitive tasks, general intelligence, and specific cognitive abilities

The relationship between inspection time (IT) and paper-and-pencil tests of cognitive ability is well documented. However, the extent to which IT relates to cognitive ability through general intelligence or through group factors such as performance has not been fully addressed. Another unresolved issue is whether IT relates to psychometric intelligence independent from other elementary cognitive tasks. The current study examined these issues in a sample of 6–13-year-old twins drawn from the Western Reserve Twin Project (WRTP) (n=568 participants). Analyses suggest that IT and other elementary tasks predict general intelligence. IT also predicts Performance ability while other elementary tasks do not. Furthermore, IT contributes variance to cognitive ability independent from other elementary tasks. These suggest that multiple indices of elementary cognitive ability are necessary to fully understand their relationship with complex psychometric measures.     

Group differences and first principal-component loadings in the Hawaii family study of cognition: a test of the generality of ‘Spearman's hypothesis’

The generality of Spearman's hypothesis that varying differences between whites and blacks on various tests of mental ability are correlated with their g-loadings was tested by analyzing group data from the Hawaii Family Study of Cognition. Data from the three largest ethnic groups tested in the Hawaii Study (Americans of Japanese, Chinese or European ancestry; total N = 5333) were subjected to a principal-component analysis and the first principal component was used as a measure of g. Ethnic group and generation (parent-offspring) differences on 15 tests of specific cognitive abilities were then correlated with their first principal-component loadings. In general, correlations between ethnic group differences and g-loadings are smaller than those recently reported for white-black differences by Jensen (1983); however, those between generation differences and g-loadings are larger. Ethnic group differences on first principal-component scores in the Hawaii Study are less than parent-offspring differences; thus, the correlation between group differences on tests of mental ability and their g-loadings may be a function of the magnitude of the group difference for general mental ability. Because a group difference on g requires group differences on tests which load on g, an observed group difference in general mental ability may necessarily result in a correlation between group differences on individual tests and their g-loadings.     

The Savanna-IQ interaction hypothesis: A critical examination of the comprehensive case presented in Kanazawa's The Intelligence Paradox

Kanazawa (2012b) has recently presented the most comprehensive case yet for his Savanna-IQ Interaction Hypothesis. According to the hypothesis, intelligence is a domain-specific adaptation which has been selected for as humans have moved away from the (evolutionarily familiar) Savanna. As such, ability in ‘evolutionarily novel’ tasks and ‘evolutionarily novel’ preferences are positively correlated with high IQ. This article will present a critical examination of the hypothesis, arguing that there is a strong case against anchoring human nature on the Savanna, the hypothesis predicts contradictory findings, there is empirical evidence against it, it is not falsifiable, and it is not necessary to explain that data which Kanazawa presents.     

Underconfidence in sensory discrimination: The interaction between experimental setting and response strategies

In a recent issue of this journal, Baranski and Petrusic (1994) presented empirical data revealing overconfidence in sensory discrimination. In this paper, we propose an explanation of Baranski and Petrusic’s results, based on an idiosyncrasy in the experimental setting that misleads subjects who are using an unwarranted symmetry assumption. Experiment 1 showed that when this hypothesis is controlled for, a large underconfidence bias is obtained with Baranski and Petrusic’s procedure. The results of Experiment 2 confirmed that overconfidence is difficult to obtain in subject-controlled sensory discrimination tasks, even for a very low proportion of correct responses. The different results obtained in sensory and cognitive tasks suggest that one should not uncritically draw parallels between confidence in sensory and cognitive judgments.     

Placing inspection time, reaction time, and perceptual speed in the broader context of cognitive ability: The VPR model in the Lothian Birth Cohort 1936

The idea that information processing speed is related to cognitive ability has a long history. Much evidence has been amassed in its support, with respect to both individual differences in general intelligence and developmental trajectories. Two so-called elementary cognitive tasks, reaction time and inspection time, have been used to compile this evidence, but most studies have used either one or the other. Relations between speed and fluid intelligence have tended to be stronger than those between speed and crystallized intelligence, but studies testing this have confounded verbal abilities with crystallized intelligence and spatial/perceptual abilities with fluid intelligence. Questions have also been raised regarding whether speed contributes directly to general intelligence or to more specific cognitive abilities to which general intelligence also contributes. We used 18 ability and speed measures in the Lothian Birth Cohort 1936, assessed at approximately age 70, to construct alternative versions of the Verbal-Perceptual-Image Rotation (Johnson & Bouchard, 2005a) model of cognitive ability to test different hypotheses regarding these issues. Though differences in the extents to which our models fit the data were relatively small, they suggested that reaction and inspection time tasks were comparable indicators of information processing speed with respect to general intelligence, that verbal and spatial abilities were similarly related to information processing speed, and that spatial, verbal, and perceptual speed abilities were more directly related to information processing speed than was general intelligence. We discuss the theoretical implications of these results.     

Dream dialogue and retrogression: neurolinguistic origins of Freud's "replay hypothesis."

At the phenomenological level, Sigmund Freud in the Traumdeutung presents dream speeches that are ubiquitous, and syntactically and pragmatically usually well-formed (despite occasional lexical anomalies), while at the generative level Freud maintains that these are playbacks, devoid of linguistic creativity, and as such do not violate the theoretically "primary-process," nondiscursive nature of the dreamwork. Neither anecdotal data nor recent systematic experimental evidence lend the "replay hypothesis" convincing support, however. This hypothesis may (like many other aspects of his dream theory) have its particular antecedents in the theoretical constraints of Freud's protopsychoanalytic "Project for a Scientific Psychology." In fact, the hypothesis can be reconciled with the neurological mechanisms of the "Project," though it cannot be specifically derived from them. Freud utilized the concept of functional retrogression from his still earlier, prepsychoanalytic work On Aphasia, thus effecting the best compromise he could between the constraints of his overall dream theory derived from the "Project" and his own observations on the phenomenology of dream speech.     

Sex differences in discrimination reversal learning in the guppy

In several mammalian and avian species, females show a higher performance than males in tasks requiring cognitive flexibility such as the discrimination reversal learning. A recent study showed that female guppies are twice as efficient as males in a reversal learning task involving yellow–red discrimination, suggesting a higher cognitive flexibility in female guppies. However, the possibility exists that the superior performance exhibited by females does not reflect a general sex difference in cognitive abilities, but instead, is confined to colour discrimination tasks. To address this issue, we compared male and female guppies in two different discrimination reversal learning tasks and we performed a meta-analysis of these experiments and the previous one involving colour discrimination. In the first experiment of this study, guppies were tested in a task requiring them to learn to select the correct arm of a T-maze in order to rejoin a group of conspecifics. In experiment 2, guppies were observed in a numerical task requiring them to discriminate between 5 and 10 dots in order to obtain a food reward. Although females outperformed males in one condition of the T-maze, we did not find any clear evidence of females’ greater reversal learning performance in either experiment. However, the meta-analysis of the three experiments supported the hypothesis of females’ greater reversal learning ability. Our data do not completely exclude the idea that female guppies have a generally higher cognitive flexibility than males; however, they suggest that the size of this sex difference might depend on the task.     

Relations between mental performance and reaction time: New aspects of an old problem

The relation between simple and complex reaction time and psychometrically determined mental performance was reexamined with 486 subjects of above-average intelligence. Various standardized tests measuring aspects of cognitive ability, memory and ability to concentrate were used. Simple and complex reaction times were measured using the Klebelsberg modification of the Mierke apparatus. Correlations between complex reaction time and mental performance as observed by other investigators were mostly confirmed. We found, however, the strongest and most consistent correlations with tests measuring short-term memory; ability to concentrate and spatial ability. On the other hand, tests known and shown again in this paper to load highly on Spearman's general factor g, such as verbal abilities; combinatoric thinking; abstraction; or calculation gave only trivial, and, in most cases, nonsignificant correlations with complex reaction time. We even observed a negative (though, for our data, not significant) correlation between g-loadings of subtests and their correlations with complex reaction time for the only complete standardized intelligence test used in this study, the “Intelligenz-Strukturtest (Amthauer).” Therefore, this study does not support the hypothesis that fast processing of complex information as measured by complex reaction time is the decisive component of the general factor of intelligence g.     

Sex differences in the personality and cognitive correlates of spatial ability

Ozer (1987) found that spatial visualization correlated with personality and verbal ability for girls but not for boys. To account for this finding, he hypothesized that "the causes of individual differences in spatial visualization [may be] different for the two sexes" (Ozer, 1987, p. 134). Although Ozer's conclusion is an intriguing one, it should be viewed with at least some skepticism until the discrepancies between his data and those of other researchers have been reconciled.