How representative are student convenience samples? A study of literacy and numeracy skills in 32 countries

Psychological research, including research into adult reading, is frequently based on convenience samples of undergraduate students. This practice raises concerns about the external validity of many accepted findings. The present study seeks to determine how strong this student sampling bias is in literacy and numeracy research. We use the nationally representative cross-national data from the Programme for the International Assessment of Adult Competencies to quantify skill differences between (i) students and the general population aged 16-65, and (ii) students and age-matched non-students aged 16-25. The median effect size for the comparison (i) of literacy scores across 32 countries was d = .56, and for comparison (ii) d = .55, which exceeds the average effect size in psychological experiments (d = .40). Numeracy comparisons (i) and (ii) showed similarly strong differences. The observed differences indicate that undergraduate students are not representative of the general population nor age-matched non-students

The English disease in Finnish compound processing: Backward transfer effects in Finnish-English bilinguals

Most English compounds are spaced compounds, whereas spelling regulations prescribe Finnish compounds to be written in a concatenated format. However, as in English, Finnish compounds are commonly spaced nowadays (e.g., piha juhla ‘garden party’), a phenomenon that we labeled the ‘English disease’. In this eye movement study with Finnish–English bilinguals we investigate whether the reading of a concatenated or illegally spaced Finnish compound is affected by the spelling of an English translation equivalent (ETE). We found that spaced Finnish compounds were read slower than their concatenated counterparts, but this effect was attenuated when ETEs were thought to be spaced. Similarly, concatenated Finnish compounds were read faster when their ETEs were also concatenated. These backward transfer effects are in line with studies that show that processing behavior in L1 is affected by a strong concurrent L2, even when the L1 is the native language as well as the dominant community language</p

How representative are student convenience samples? A study of literacy and numeracy skills in 32 countries

Psychological research, including research into adult reading, is frequently based on convenience samples of undergraduate students. This practice raises concerns about the external validity of many accepted findings. The present study seeks to determine how strong this student sampling bias is in literacy and numeracy research. We use the nationally representative cross-national data from the Programme for the International Assessment of Adult Competencies to quantify skill differences between (i) students and the general population aged 16-65, and (ii) students and age-matched non-students aged 16-25. The median effect size for the comparison (i) of literacy scores across 32 countries was d = .56, and for comparison (ii) d = .55, which exceeds the average effect size in psychological experiments (d = .40). Numeracy comparisons (i) and (ii) showed similarly strong differences. The observed differences indicate that undergraduate students are not representative of the general population nor age-matched non-students

A Brief Critique of the TATES Procedure

The Trait-based test that uses the Extended Simes procedure (TATES) was developed as a method for conducting multivariate GWAS for correlated phenotypes whose underlying genetic architecture is complex. In this paper, we provide a brief methodological critique of the TATES method using simulated examples and a mathematical proof. Our simulated examples using correlated phenotypes show that the Type I error rate is higher than expected, and that more TATES p values fall outside of the confidence interval relative to expectation. Thus the method may result in systematic inflation when used with correlated phenotypes. In a mathematical proof we further demonstrate that the distribution of TATES p values deviates from expectation in a manner indicative of inflation. Our findings indicate the need for caution when using TATES for multivariate GWAS of correlated phenotypes

Genetic and neurophysiological correlates of the age of onset of alcohol use disorders in adolescents and young adults.

Discrete time survival analysis was used to assess the age-specific association of event-related oscillations (EROs) and CHRM2 gene variants on the onset of regular alcohol use and alcohol dependence. The subjects were 2,938 adolescents and young adults ages 12-25. Results showed that the CHRM2 gene variants and ERO risk factors had hazards which varied considerably with age. The bulk of the significant age-specific associations occurred in those whose age of onset was under 16. These associations were concentrated in those subjects who at some time took an illicit drug. These results are consistent with studies which associate greater rates of alcohol dependence among those who begin drinking at an early age. The age specificity of the genetic and neurophysiological factors is consistent with recent studies of adolescent brain development, which locate an interval of heightened vulnerability to substance use disorders in the early to mid teens

How phenotype and developmental stage affect the genes we find: GABRA2 and impulsivity

CONTEXT: The detection and replication of genes involved in psychiatric outcome has been notoriously difficult. Phenotypic measurement has been offered as one explanation, although most of this discussion has focused on problems with binary diagnoses. OBJECTIVE: This article focuses on two additional components of phenotypic measurement that deserve further consideration in evaluating genetic associations: (1) the measure used to reflect the outcome of interest, and (2) the developmental stage of the study population. We focus our discussion of these issues around the construct of impulsivity and externalizing disorders, and the association of these measures with a specific gene, GABRA2. DESIGN, SETTING, AND PARTICIPANTS: Data were analyzed from the Collaborative Study on the Genetics of Alcoholism Phase IV assessment of adolescents and young adults (ages 12–26; N = 2,128). MAIN OUTCOME MEASURES: Alcohol dependence, illicit drug dependence, childhood conduct disorder, and adult antisocial personality disorder symptoms were measured by psychiatric interview; Achenbach youth/adult self-report externalizing scale; Zuckerman Sensation-Seeking scale; Barratt Impulsivity scale; NEO extraversion and consciousness. RESULTS: GABRA2 was associated with subclinical levels of externalizing behavior as measured by the Achenbach in both the adolescent and young adult samples. Contrary to previous associations in adult samples, it was not associated with clinical-level DSM symptom counts of any externalizing disorders in these younger samples. There was also association with sensation-seeking and extraversion, but only in the adolescent sample. There was no association with the Barratt impulsivity scale or conscientiousness. CONCLUSIONS: Our results suggest that the pathway by which GABRA2 initially confers risk for eventual alcohol problems begins with a predisposition to sensation-seeking early in adolescence. The findings support the heterogeneous nature of impulsivity and demonstrate that both the measure used to assess a construct of interest and the age of the participants can have profound implications for the detection of genetic associations