Jan-Eric Gustafsson

A Unifying Model for the Structure of Intellectual Abilities.

Models of the structure of cognitive abilities suggested by Spearman, Thurstone, Guilford, Vernon and Cattell-Horn are reviewed. It is noted that some of the models include a general intellectual factor (g) while others do not. It is also noted that some models are nonhierarchical, while in others more narrow abilities are subsumed under broader abilities in a hierarchical pattern. An empirical study in which a test battery of 16 tests was administered to some 1000 subjects in the 6th grade is reported. Using the LISREL technique to test different models, good support is obtained for oblique primary factors in the Thurstone tradition as well as for the second-order factors fluid intelligence, crystallized intelligence, and general visualization hypothesized by Cattell and Horn. It is also found, however, that the second-order factor of fluid intelligence i is identical with a third-order g-factor. On the basis of these results a three-level model (the HILI-model) is suggested, with the g-factor at the top, two broad factors reflecting the ability to deal with verbal and figural information, respectively, at the second-order level, and the primary factors in the Thurstone and Guilford tradition at the lowest level. It is argued that most previously suggested models are special cases of the HILI-model.

Individuals, schools, and neighborhood: a multilevel longitudinal study of variation in incidence of psychotic disorders

CONTEXT Incidence of schizophrenia and other nonaffective psychoses is greater in urban than rural areas, but the reason is unclear. Few studies have examined whether both individual and neighborhood characteristics can explain this association. Furthermore, as has been shown for ethnicity, the effect of individual characteristics may depend on neighborhood context. OBJECTIVES To examine (1) whether individual, school, or area characteristics are associated with psychosis and can explain the association with urbanicity and (2) whether effects of individual characteristics on risk of psychosis vary according to school context (reflecting both peer group and neighborhood effects). DESIGN Multilevel longitudinal study of all individuals born in Sweden in 1972 and 1977. Diagnoses were identified through linkage with the Swedish National Patient Register until December 31, 2003. SETTING Population-based. PARTICIPANTS A total of 203 829 individuals with data at individual, school, municipality, and county levels. MAIN OUTCOME MEASURES Any nonaffective psychosis, including schizophrenia (881 subjects; 0.43% cumulative incidence). For the study of interactions, the outcome was any psychosis (1944 subjects; 0.95% cumulative incidence). RESULTS Almost all the variance in risk of nonaffective psychosis was explained by individual-level rather than higher-level variation. An association between urbanicity and nonaffective psychosis was explained by higher-level characteristics, primarily school-level social fragmentation. We observed cross-level interactions between individual- and school-level markers of ethnicity, social fragmentation, and deprivation on risk of developing any psychotic disorder, all with qualitative patterns of interaction. CONCLUSIONS The association between urbanicity and psychosis appears to be a reflection of increased social fragmentation present within cities. The qualitative interactions observed are consistent with a hypothesis that certain characteristics that define individuals as being different from most other people in their local environment may increase risk of psychosis. These findings have potentially important implications for understanding the etiology of psychotic disorders and for informing social policy.

Decline in cognitive performance between ages 13 and 18 years and the risk for psychosis in adulthood: a Swedish longitudinal cohort study in males

CONTEXT Clear evidence from many prospective, population-based studies indicates that patients who develop psychosis in adulthood experienced various cognitive deficits during childhood and adolescence. However, it is unclear whether these deficits become more severe during adolescence. OBJECTIVE To assess the influence of cognitive developmental trajectories in adolescence and young adulthood on the risk for psychosis in adulthood. DESIGN Longitudinal cohort study. SETTING Academic research. POPULATION-BASED COHORTS: Four population-based cohorts of adolescent boys and young men born in Sweden in 1953, 1967, 1972, and 1977, totaling 10,717 individuals, and followed up through December 31, 2006. EXPOSURE Scores on tests of verbal, spatial, and inductive ability at age 13 years and in equivalent tests at army conscription (age 18 years). MAIN OUTCOME MEASURE Hospital admissions for nonaffective or affective psychoses in adulthood. RESULTS A relative decline (compared with the unaffected population) in verbal ability between ages 13 and 18 years was associated with increased risk for schizophrenia and for other nonaffective and affective psychoses (adjusted hazard ratio for schizophrenia for an increase of 1 SD in verbal ability, 0.59; 95% CI, 0.40-0.88; P = .009). Decline between ages 13 and 18 years was a much stronger predictor of psychosis than the verbal ability score at age 18 years alone. The association remained significant after adjustment for urbanicity, parental educational level, and family history of psychosis and persisted when cases with onset before age 25 years were excluded, indicating that this was not a prodromal effect. CONCLUSIONS A relative decline in cognitive performance in adolescence and young adulthood, particularly in verbal ability, is associated with increased risk for psychosis in adulthood, and a relative decline in verbal ability between ages 13 and 18 years is a stronger predictor of psychosis than verbal ability at age 18 years alone. This suggests an impairment of late neurodevelopment affecting the acquisition of verbal skills in adolescent boys and young men who later develop psychosis.

Measuring Socioeconomic Status at Individual and Collective Levels

This study investigated the multilevel dimensionality of socioeconomic status and its relationship to reading achievement in 23 countries. Different factor structures of SES were found at different levels’ observations and in different countries. The study showed that the cultural dimension strongly related to student reading performance, while the school general capital dimension explained a large part of the between-school reading achievement differences. Most interestingly, the factor relationship between SES and reading achievement at the school level varies greatly across countries. It was argued that these variations might be due to the differences in the centralized versus decentralized educational finance, tracking mechanism and some social characteristics in different countries.

Evaluating competing models of the relationship between inspection time and psychometric intelligence

Abstract Confirmatory factor analysis (CFA) was used to test models of the relationship between inspection time (IT) and psychometric measures of intelligence (the eleven subtests of the Wechsler Adult Intelligence Scale-Revised). The sample consisted of 134 healthy adults and was broadly representative of the adult United Kingdom population in terms of the distributions of age and social class. A Nested Factors parameterization consisting of g plus three orthogonal group factors with IT loading on all factors provided a reasonably good fit to the data. Variants on this model that incorporated theoretical and empirically derived constraints were tested; constraining IT to have zero loadings on all factors produced a significant deterioration in fit. Constraining IT to load only on General Intelligence ( g ) and Perceptual Organization did not produce a significant deterioration; nested variants on this latter model in which IT was constrained to load on either of these two factors alone produced a significant deterioration in fit.

Sentence repetition is a measure of children's language skills rather than working memory limitations

Sentence repetition tasks are widely used in the diagnosis and assessment of children with language difficulties. This paper seeks to clarify the nature of sentence repetition tasks and their relationship to other language skills. We present the results from a 2-year longitudinal study of 216 children. Children were assessed on measures of sentence repetition, vocabulary knowledge and grammatical skills three times at approximately yearly intervals starting at age 4. Sentence repetition was not a unique longitudinal predictor of the growth of language skills. A unidimensional language latent factor (defined by sentence repetition, vocabulary knowledge and grammatical skills) provided an excellent fit to the data, and language abilities showed a high degree of longitudinal stability. Sentence repetition is best seen as a reflection of an underlying language ability factor rather than as a measure of a separate construct with a specific role in language processing. Sentence repetition appears to be a valuable tool for language assessment because it draws upon a wide range of language processing skills.

Repeated measurements of mood during psychologic treatment of dental fear

The aims of the present study were to analyze mood changes during psychologic treatment of dental fear by assessing the rate of improvement. Twenty-one patients who refused conventional dental treatment and reported extreme dental anxiety participated in the study. Levels of dental anxiety and mood were measured with the Dental Anxiety Scale (DAS) and a Mood Adjective Checklist (MACL). MACL included two dimensions, degree of relaxation (r) and pleasantness (h) as experienced in a dental situation. Mood was monitored at each treatment session from base line to termination of the therapy (eight measurements). Two different treatment modalities were used, one with a more cognitive approach (n = 9) and one emphasizing the relaxation component (n = 12). A hierarchical linear models approach was applied to analyze individual change with repeated measurements. The results showed that positive mood changes over time were statistically significant. The mean improvement in mood scores per week and session was estimated for MACL(r) and MACL(h) to be 0.14/week and 0.09/week, respectively. The growth was not affected by DAS levels or treatment mode. This study also illustrated a powerful method for analyzing a longitudinal clinical trial design with repeated measurements.

Hierarchical models of ability at individual and class levels

Abstract Scores in ability tests administered to students in Grades 4–6 ( n = 1,274) and Grades 7–9 ( n = 1,310) were simultaneously factor analyzed at class and individual levels. Muthens (1990) multilevel factor analysis was used to test hierarchical models of intelligence. At the individual level the general factor was most highly loaded on “fluid” abilities. Also, there were residual factors for speed, verbal comprehension, spatial visualization, and numerical facility as well as test-specific factors derived from parallel versions of the tests. At the class level three common factors were established: one general factor more highly loaded on “crystallized” than on fluid abilities, and residual common factors for speed and, in Grades 7–9, verbal comprehension. The between factors accounted for relatively more variance in Grades 7–9 than in Grades 4–6 due to an intervening reorganization of classes based on choice of more or less academic courses. Demographic differences between neighborhoods, self-selection between academic and general programs, and variations in instruction and test administration were used to explain the between-class factors.

Effects of International Comparative Studies on Educational Quality on the Quality of Educational Research

Large-scale survey studies of educational achievement are becoming increasingly frequent, and they are visibly present in both educational policy debates and within the educational research community. One main aim of these studies is to provide descriptions of inputs, processes and outcomes, and another aim is to provide explanations of how different factors interrelate to produce educational outcomes. These aims are difficult to reach, which in combination with the fact that the comparative studies are typically more policy driven than theory driven, are reasons why these studies are contested on quality grounds. In this article, a set of fundamental methodological challenges related to the validity of the measurement instruments and to the possibility of making inferences about causality are identified and discussed in relation to examples of different studies. Strengths and weaknesses of different research approaches are discussed, and it is proposed that the dichotomy between qualitative and quantitative approaches should be replaced with distinctions between low-and high-level inference approaches with respect to data, generalization and explanation. It is concluded that while the international studies easily invite misuse and misinterpretation, they also offer possibilities for improving the quality of educational research, because the high-quality data generated by these studies can be taken advantage of in research on causal effects of factors in and out of educational systems.

Causal inference in educational effectiveness research: a comparison of three methods to investigate effects of homework on student achievement 1

In educational effectiveness research, it frequently has proven difficult to make credible inferences about cause and effect relations. The article first identifies the main categories of threats to valid causal inference from observational data, and discusses designs and analytic approaches which protect against them. With the use of data from 22 countries which participated both in the Trends in International Mathematics and Science Study (TIMSS) 2003 and TIMSS 2008 with samples of Grade 8 students, 3 different methods are then applied to investigate effects of amount of time spent on homework on mathematics achievement: (a) 2-level regression, which is applied to separate student-level relations from class-level relations; (b) instrumental variables regression, using teacher-reported homework time to instrument student-reported homework time; and (c) a difference-in-differences analysis investigating country-level change between 2003 and 2007. All 3 methods showed that there is a positive effect of homework time on student achievement.