Equivalency and reliability of vectors of g-loadings across different methods of estimation and sample sizes

We examine the variability in g-loadings with particular focus on the differential stability (i.e., rank order inconsistencies) of the vector of loadings due to sample size and method of estimation. Our results, based on 1600 factor-analyses, show that different methods of estimation require different sample sizes to achieve the same level of stability in loadings. However, all methods examined yielded reliable vectors when sample sizes of N = 400 were used. Some methods yielded reliable vectors with sample sizes of N = 200. Such results provide guidelines for choosing an appropriate sample size when g-loadings are of interest.     

Identifying g: A review of current factor analytic practices in the science of mental abilities

Factor analysis is arguably one of the most important tools in the science of mental abilities. While many studies have been conducted to make recommendations regarding “best practices” concerning its use, it is unknown the degree to which contemporary ability researchers abide by those standards. The current study sought to evaluate the typical practices of contemporary ability researchers. We analyzed articles reporting factor analyses of cognitive ability tests administered to adult samples over a 12 year period. Results suggest that, in aggregate, the science of mental abilities seems to be doing well with respect to the issues of sample size, number of indicators (relative to number of factors) and breadth of indicators. Further, our results suggest that the majority of ability researchers are using methods of factor analysis that allow for the identification of a g factor. However, 14.57% failed to use a method that allowed a common factor to emerge. These results provide insights regarding the methodological quality of the science of mental abilities, and will hopefully encourage further “introspective” research into the science of mental abilities.     

Expanding the g-nexus: Further evidence regarding the relations among national IQ, religiosity and national health outcomes

The current study seeks to better understand how religiosity and health are positioned within the g-nexus. Specifically, the degree to which differences in average IQ across nations is associated with differences in national religiosity (i.e., belief rate) and national health statistics independent of differences in national wealth is examined. Consistent with expectations, results show that, independent of national wealth and belief rate, IQ has a positive influence on national health as indicated by fertility rate, infant mortality rate, maternal mortality rate, and deaths due to HIV/AIDS, and life expectancy. Additionally, as hypothesized, IQ and belief rate interacted to influence reproductive health (i.e., fertility rate, infant- and maternal mortality). Specifically, high IQ acts as a buffer against the negative effects of belief rate; when IQ is high belief rate has no effect, but when IQ is low belief rate has a strong negative effect. The pattern of findings from this study, combined with previous research, serve to confirm that general cognitive ability (i.e., the g-factor) is an important and central node within a larger nexus of psychological and social variables. Theoretical and epidemiological implications are discussed.     

IQ and the wealth of states

In IQ and the Wealth of Nations (2002), Lynn and Vanhanen estimate the mean IQs of 185 nations and demonstrate that national IQs strongly correlate with the macroeconomic performance of the nations, explaining about half of the variance in GDP per capita. I seek to replicate Lynn and Vanhanen's results across states within the United States. I first estimate “state IQs” from the SAT data, and show that the state IQs correlate moderately with the economic performance of the states, explaining about a quarter of the variance in GSP (gross state product) per capita.     

Jensen Effects and African/Coloured/Indian/White differences on Raven's Standard Progressive Matrices in South Africa

A test is made to determine whether various ethnic group differences on tests of cognitive performance in South Africa are like the Black/White differences in the United States in being positively associated with a tests' g loadings, where g is the general factor of intelligence. A non-parametric re-analysis is made of data from 1056 White, 1063 Indian, 778 mixed-race “Coloured,” and 1093 Black 14 year olds on the Raven's Standard Progressive Matrices Test in South Africa, given without time limits by Owen (1992) [Personality and Individual Differences, 13, 149]. The new analyses showed that the more highly correlated an item was with g, the more it predicted the White/Indian/Coloured/African differences on the test (Spearman's rhos from 0.35 to 0.85; all Ps<0.01). The effects remained regardless of which group g was extracted from. Understanding group differences around the world requires new research on the nature and nurture of g.     

Correlation between general factors for personality and cognitive skills in the National Merit twin sample

General factors of personality (based on the California Psychological Inventory) and cognitive skill (the National Merit Scholarship Qualifying Test selection score) were correlated .284 in a sample of 490 monozygotic and 317 dizygotic twin pairs. The correlation was partitioned into genetic, and shared and unshared environmental sources: approximately 39%, 50% and 11%, respectively. The results offered some support to a theory that such a correlation may reflect evolutionary trends, although questions remained about the role of nonadditive genetic variance and the nature of the selection involved.     

The dependability of the general factor of intelligence: Why small, single-factor models do not adequately represent g

Floyd, Shands, Rafael, Bergeron and McGrew (2009) used generalizability theory to test the reliability of general-factor loadings and to compare three different sources of error in them: the test battery size, the test battery composition, the factor-extraction technique, and their interactions. They found that their general-factor loadings were moderately to strongly dependable. We replicated the methods of Floyd et al. (2009) in a different sample of tests, from the Minnesota Study of Twins Reared Apart (MISTRA). Our first hypothesis was that, given the greater diversity of the tests in MISTRA, the general-factor loadings would be less dependable than in Floyd et al. (2009). Our second hypothesis, contrary to the positions of Floyd et al. (2009) and Jensen and Weng (1994), was that the general factors from the small, randomly-formed test batteries would differ substantively from the general factor from a well-specified hierarchical model of all available tests. Subtests from MISTRA were randomly selected to form independent and overlapping batteries of 2, 4 and 8 tests in size, and the general-factor loadings of eight probe tests were obtained in each battery by principal components analysis, principal factor analysis and maximum likelihood estimation. Results initially indicated that the general-factor loadings were unexpectedly more dependable than in Floyd et al. (2009); however, further analysis revealed that this was due to the greater diversity of our probe tests. After adjustment for this difference in diversity, and consideration of the representativeness of our probe tests versus those of Floyd et al. (2009), our first hypothesis of lower dependability was confirmed in the overlapping batteries, but not the independent ones. To test the second hypothesis, we correlated g factor scores from the random test batteries with g factor scores from the VPR model; we also calculated special coefficients of congruence on the same relation. Consistent with our second hypothesis, the general factors from small non-hierarchical models were found to not be reliable enough for the purposes of theoretical research. We discuss appropriate standards for the construction and factor analysis of intelligence test batteries.     

On the myth and the reality of the temporal validity degradation of general mental ability test scores

Claims of changes in the validity coefficients associated with general mental ability (GMA) tests due to the passage of time (i.e., temporal validity degradation) have been the focus of an on-going debate in applied psychology. To evaluate whether and, if so, under what conditions this degradation may occur, we integrate evidence from multiple sub-disciplines of psychology. The temporal stability of construct validity is considered in light of the evidence regarding the differential stability of g and the invariance of measurement properties of GMA tests over the adult life-span. The temporal stability of criterion-related validity is considered in light of evidence from long-term predictive validity studies in educational and occupational realms. The evidence gained from this broad-ranging review suggests that temporal degradation of the construct- and criterion-related validity of ability test scores may not be as ubiquitous as some have previously concluded. Rather, it appears that both construct and criterion-related validity coefficients are reasonably robust over time and that any apparent degradation of criterion-related validity coefficients has more to do with changes in the determinants of task performance and changes in the nature of the criterion domain rather temporal degradation per se (i.e., the age of the test scores). A key exception to the conclusion that temporal validity degradation is more myth than reality concerns decision validity. Although the evidence is sparse, it is likely that the utility of a given GMA test score for making diagnostic decisions about an individual deteriorates over time. Importantly, we also note several areas in need of additional and more rigorous research before strong conclusions can be supported.     

Genetic and environmental influences on the Verbal-Perceptual-Image Rotation (VPR) model of the structure of mental abilities in the Minnesota study of twins reared apart

In previous papers [Johnson, W., & Bouchard Jr., T. J. (2005a). Constructive Replication of the Visual-Perceptual-Image Rotation (VPR) Model in Thurstone's (1941) Battery of 60 Tests of Mental Ability. Intelligence, 33, 417–430.] [Johnson, W., & Bouchard Jr., T. J. (2005b). The Structure of Human Intelligence: It's Verbal, perceptual, and image rotation (VPR), not Fluid and Crystallized. Intelligence, 33, 393–416.] we have proposed the Verbal, perceptual, and image rotation (VPR) model of the structure of mental abilities. The VPR model is hierarchical, with a g factor that contributes strongly to broad verbal, perceptual, and image rotation abilities, which in turn contribute to 8 more specialized abilities. The verbal and perceptual abilities, though separable, are highly correlated, as are the perceptual and mental rotation abilities. The verbal and mental rotation abilities are much less correlated. In this study we used the twin sample in the Minnesota Study of Twins Reared Apart to estimate the genetic and environmental influences and the correlations among them at each order of the VPR model. Genetic influences accounted for 67–79% of the variance throughout the model, with the exception of the second-stratum Content Memory factor, which showed 33% genetic influence. These influences could not be attributed to assessed similarity of rearing environment. Genetic correlations closely mirrored the phenotypic correlations. Together, these findings substantiate the theory that the entire structure of mental abilities is strongly influenced by genes.     

Subregion-specific dendritic spine abnormalities in the hippocampus of Fmr1 KO mice

Fragile X syndrome (FXS) is the most common inherited form of mental retardation and is caused by the lack of fragile X mental retardation protein (FMRP). In the brain, spine abnormalities have been reported in both patients with FXS and Fmr1 knockout mice. This altered spine morphology has been linked to disturbed synaptic transmission related to altered signaling in the excitatory metabotropic glutamate receptor 5 (mGluR5) pathway. We investigated hippocampal protrusion morphology in adult Fmr1 knockout mice. Our results show a hippocampal CA1-specific altered protrusion phenotype, which was absent in the CA3 region of the hippocampus. This suggests a subregion-specific function of FMRP in synaptic plasticity in the brain.     

The quiet of the fierce barracuda: masculinity and aggression in Pohnpei, Micronesia

This paper provides historical background on youth violence for the understudied indigenous Micronesian culture of Pohnpei. Aggression has long been of high cultural value for men in Pohnpei. Masculinity was assessed on a man's power and authority (manaman), as generally indicated by his possession of a ranked title within the chiefly hierarchy. For the very highest ones, a man's title was awarded on the basis of matrilineal genealogical connections; for all other titles, more weight was placed on individual achievements (with the help of relatives, undertaken for the chiefs) in the most competitive realms of society—bravery in warfare and prestations (i.e., the offering of valuable gifts that are due to people of high status) at feasts. Masculinity was also assessed in terms of a man's heterosexual prowess. A man's successes in these realms were based on his possession of special knowledge, skills, and other characteristics—but typically, these were carefully secluded from public notice and dramatically revealed only on special occasions. One Pohnpeian proverb states, “The quiet of the fierce barracuda.” Like a barracuda, a man lies quietly in the water, waiting for his prey to appear; when it does, he rises swiftly and surely to the attack.Many changes to Pohnpeian culture have resulted from nearly two centuries of various foreign activities on the island. This paper explores the changes in indigenous masculinity and aggression during early foreign contact by whalers, traders, beachcombers, and missionaries who used Pohnpei as a major port of call; over four successive colonial regimes in Micronesia that had headquarters in Pohnpei; during Japanese militarization of the island in World War II; and in the American rule that quickly followed. The indigenous Pohnpeian cultural notions of masculinity and aggression, with modifications over these centuries of contact, are ones that Pohnpeians carry with them in diaspora, primarily to the United States, especially in the more developed Pacific Islands located nearby, such as Guam and Hawai'i.     

Unconsciously Poisoning the Roots: Psychological Dynamics of the Bible in Jewish/Christian Conflict

The persistence of antisemitism in Christian cultures despite the irrationality and destructiveness of its myths and attitudes has led more than one writer to consider that it may be deeply rooted in psychological dynamics, both individual and social. Likewise, much has been written about how the New Testament writings, especially certain passages in the Gospels, reflect a bitter split between the emerging Christian community and other Jewish groups. Seldom, however, are these two avenues of exploration brought together, asking how psychological mechanisms of defense and the formation of the biblical texts interact. In a recent book, The Jew and Deicide: The Origin of an Archetype (Davis, 2003), psychologist Frederick B. Davis attempted to do just that. Unfortunately, his presentation is deeply flawed by his lack of familiarity with basic New Testament studies and methods. His fundamental premise is sound—that the interplay of the texts, the communities that created them, and their subsequent interpreters evidence psychological dynamics that fuel an ongoing conflict. In this paper, I will suggest how those dynamics were active within the first century Christian community and were expressed in New Testament writings, and how those same dynamics are stimulated in later readers.Paper originally presented March 22, 2004. In D. MacDonald (Chair), New Testament Texts and Traditions. Session conducted at the Western regional meeting of the Society of Biblical Literature, Whittier, CA     

Developmental study of multiple memory stages in the cuttlefish, Sepia officinalis

The inhibition of predatory behavior observed during the "prawn-in-the-tube" procedure has been extensively used in studies of cuttlefish learning. The present study examines the effect of age on the conditioning of this response in the cuttlefish, Sepia officinalis. Data show that a significant increase in acquisition performance occurs between 15 and 21 days of age. The retention curves in 8- and 15-day-old cuttlefish show a monotonic memory process, presumably reflecting the presence of only short-term memory. In 21-day-old cuttlefish, there are two distinct processes which could be a labile short-term memory, and a subsequent intermediate memory. These mnesic systems seem to become more effective over the course of post-embryonic development. Moreover, the retention curves obtained in the oldest cuttlefish (30- and 90-day-old) bear a close resemblance to that observed in adults. These behavioral findings will allow further work on the cellular and molecular mechanisms of learning and memory in the cuttlefish.     

Amount of General Factor Saturation in the Beck Anxiety Inventory Responses of Outpatients with Anxiety Disorders

To ascertain the amount of general factor saturation underlying the Beck Anxiety Inventory (BAI; Beck and Steer 1993) responses of anxious patients, the BAI was administered to 525 outpatients with DSM-IV-TR anxiety disorders. McDonald’s omega_hierarchical(ω _h) (Zinbarg et al. 2005) was calculated to estimate the amount of general factor saturation; ω _h is the amount of variance explained by a general (second-order) factor underlying a scale composed of multiple items divided by the total amount of variance explained by all of the scale’s items. An iterated principal-factor analysis was first performed and followed by a Schmid-Leiman transformation to determine the amount of variance explained by the second-order factor. ω _h was 0.70 [95% CI 0.66–0.72], and this value was discussed as supporting the current practice of summing the 21 symptom ratings of the BAI to estimate the overall severity of self-reported anxiety.

Sources of Cognitive Exploration: Genetic Variation in the Prefrontal Dopamine System Predicts Openness/Intellect

The personality trait Openness/Intellect reflects the tendency to be imaginative, curious, perceptive, artistic, and intellectual - all characteristics that involve cognitive exploration. Little is known about the biological basis of Openness/Intellect, but the trait has been linked to cognitive functions of prefrontal cortex, and the neurotransmitter dopamine plays a key role in motivation to explore. The hypothesis that dopamine is involved in Openness/Intellect was supported by examining its association with two genes that are central components of the prefrontal dopaminergic system. In two demographically different samples (children: N = 608; adults: N = 214), variation in the dopamine D4 receptor gene (DRD4) and the catechol-O-methyltransferase gene (COMT) predicted Openness/Intellect, as main effects in the child sample and as a gene-gene interaction in adults.     

Comparison of impulsiveness, venturesomeness and empathy (I7) structure in English and Spanish samples: Analysis of different structural equation models

The present study analyzed the factorial structure of the I₇ Impulsiveness questionnaire (Impulsiveness, Venturesomeness and Empathy) with a Spanish sample of 742 males and 1.075 females, through exploratory and confirmatory factorial analysis. In relation to the original English data, a three-factor structure showed global congruency coefficients of 0.92 and 0.94 for men and women. Venturesomeness had a modest congruency for males (0.83). A cross-validation analytical strategy showed that the 24-item I₇ was invariant only for the female sample. A subsequent exploratory factor analysis with 24 items showed a sound factor structure. The 24-item version showed the best and most robust structure and similar internal consistency coefficients in regard to the 54-item version. No important differences were founded between I₇ long and short versions with impulsiveness scales of ZKPQ, BIS-10 and SPSRQ.