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Over the past few years, more attention has been paid to jingle and jangle fallacies in psychological science. Jingle fallacies arise when two or more distinct psychological phenomena are erroneously labeled with the same term, while jangle fallacies occur when different terms are used to describe the same phenomenon. Jingle and jangle fallacies emerge due to the vague linkage between psychological theories and their practical implementation in empirical studies, compounded by variations in study designs, methodologies, and applying different statistical procedures' algorithms. Despite progress in organizing scientific findings via systematic reviews and meta-analyses, effective strategies to prevent these fallacies are still lacking. This paper explores the integration of several approaches with the potential to identify and mitigate jingle and jangle fallacies within psychological science. Essentially, organizing studies according to their specifications, which include theoretical background, methods, study designs, and results, alongside a combinatorial algorithm and flexible inclusion criteria, may indeed represent a feasible approach. A jinglefallacy detector arises when identical specifications lead to disparate outcomes, whereas jangle-fallacy indicators could operate on the premise that varying specifications consistently yield overrandomly similar results. We discuss the role of advanced computational technologies, such as Natural Language Processing (NLP), in identifying these fallacies. In conclusion, addressing jingle and jangle fallacies requires a comprehensive approach that considers all levels and phases of psychological science. [ABSTRACT FROM AUTHOR]

According to family systems theory, a family is regarded as an organized whole and relations within this system are interconnected. However, it is not clear to date whether the interparental and the sibling relationship are associated and, if such an association exists, whether it is positive or negative. Previous findings on the associations between the interparental and sibling relationships are inconsistent and there is as yet no pertinent review or meta-analysis. Therefore, this systematic review and meta-analysis set out (1) to aggregate previous studies investigating the links between the interparental and sibling relationships and (2) to examine potential moderators in this link. Based on 47 studies reporting 234 effect sizes (N = 29,746 from six nations; 6–12 years; 49% boys), meta-analytic results suggest a small positive correlation between interparental and sibling relationship quality (r =.14). Only the percentage of male children in the sample moderated this effect. Sex composition of sibling dyad and source of publication affected whether positive or negative associations were found. The findings support a growing consensus that family relations do not function in isolation, but are mutually interdependent, which should be considered in clinical practice. [ABSTRACT FROM AUTHOR]

The present meta-analyses investigated the widely used contingent-capture protocol. Contingent-capture theory postulates that only top-down matching stimuli capture attention. Evidence comes from the contingent-capture protocol, in which participants search for a predefined target stimulus preceded by a spatial cue. The cue is typically uninformative of the target's position but either presented at target position (valid condition) or away from the target (invalid condition). The common finding is that seemingly only top-down matching cues capture attention as shown by a selective cueing effect (faster responses in valid than invalid conditions) for cues with a feature similar to the searched-for target only, but not for cues without target-similar feature. The origin of this "contingent-capture effect" is, however, debated. One alternative explanation is that intertrial priming—the priming of attention capture by the cue in a given trial by attending to a feature-similar target in the preceding trial—mediates the contingent-capture effect. Alternatively, the rapid-disengagement account argues that all salient stimuli capture attention initially, but that the disengagement from non-matching cues is rapid. The present meta-analyses shed light on this debate by (a) identifying moderators of the size of reported contingent-capture effects (64 experiments) and (b) analyzing pure (blocked) versus mixed presentation of different targets as well as summarizing results of published intertrial priming studies (12 experiments) in the contingent-capture protocol. We found target-singleton versus non-singleton status and pure versus mixed presentation of different targets to be reliable moderators. Furthermore, results indicated the presence of publication bias. Otherwise, the contingent-capture theory was supported, but we discuss additional factors that must be taken into account for a full account of the results. [ABSTRACT FROM AUTHOR]

Background: Till et al. (2016) reported that in an Austrian sample approximately one in ten respondents incorrectly believed that Austria still practices, or recently practiced, the death penalty, and that there is a positive association between the amount of weekly television viewing and this gross misperception of the Austrian justice system. Methods: An endorsed, prereviewed, preregistered close (N = 597) served to test the veracity of these reported effects. This was coupled with the conceptual extension part, which (a) investigated the potential influence of watching American crime series, (b) accounted for further possible confounds, and (c) tested the generalizability of the effect of television viewing to online streaming. Results: Online survey data (N = 597) replicated the one-in-ten prevalence of incorrect answers with the 5-item death penalty questionnaire used in the original study, but not, when asking directly about Austria's death penalty practices (prevalence: 0.3%). Younger age, but not the amount of television viewing or online streaming, suggestibility, or preferred TV genre consistently predicted incorrect answers in the death penalty questionnaire. Incorrect answers were Mokken-scalable (i.e., formed a common scale, complying with a non-parametric item response model) and were highly consistent. In contrast to the replication study results, a small meta-analysis of all available evidence (three studies, including the present replication) suggested that the aggregate effect of television viewing nominally was significant, albeit small. Conclusion: The replication study yielded mixed results, which indicate the perception of a high prevalence of beliefs that there is capital punishment in a country without death penalty probably is due to a faultily designed questionnaire and thus a research artifact. Also, positive associations of television viewing with such beliefs likely are only small at best. [ABSTRACT FROM AUTHOR]

In the last decade, the number of investigations of the beliefs in conspiracy theories has begun to increase in the fields of social, differential, and experimental psychology. A considerable number of variables have been suggested as predictors of conspiracy beliefs, amongst them personality factors such as low agreeableness (as disagreeableness is associated with suspicion and antagonism) and high openness to experience (due to its positive association to seek out unusual and novel ideas). The association between agreeableness, openness to experience and conspiracy beliefs remains unclear in the literature. The present study reviews the literature of psychological studies investigating conspiracy beliefs. Additionally, the association between Big Five personality factors and conspiracy beliefs is analyzed meta-analytically using random-effects models. Ninety-six studies were identified for the systematic review. A comprehensive account of predictors, consequences, operationalization, questionnaires, and most prominent conspiracy theories is presented. For meta-analysis, 74 effect sizes from 13 studies were extracted. The psychological literature on predictors of conspiracy beliefs can be divided in approaches either with a pathological (e.g., paranoia) or socio-political focus (e.g., perceived powerlessness). Generally, there is a lack of theoretical frameworks in this young area of research. Meta-analysis revealed that agreeableness, openness to experience, and the remaining Big Five personality factors were not significantly associated with conspiracy beliefs if effect sizes are aggregated. Considerable heterogeneity in designs and operationalization characterizes the field. This article provides an overview of instrumentation, study designs, and current state of knowledge in an effort toward advancement and consensus in the study of conspiracy beliefs. [ABSTRACT FROM AUTHOR]

Background: The initial preference task (IPT) is an implicit measure that has featured prominently in the literature and enjoys high popularity because it offers to provide an unobtrusive and objective assessment of self-esteem that is easy to administer. However, its use for self-esteem assessment may be limited because of weak associations with direct personality measures. Moreover, moderator effects of sample- and study-related variables need investigation to determine the value of IPT-based assessments of self-esteem. Methods: Conventional and grey-literature database searches, as well as screening of reference lists of obtained articles, yielded a total of 105 independent healthy adult samples (N = 17,777) originating from 60 studies. Summary effect estimates and subgroup analyses for potential effect moderators (e.g., administration order, algorithm, rating type) were calculated by means of meta-analytic random- and mixed-effects models. Moreover, we accounted for potential influences of publication year, publication status (published vs. not), and participant sex in a weighted stepwise hierarchical multiple meta-regression. We tested for dissemination bias through six methods. Results: There was no noteworthy correlation between IPT-based implicit and explicit self-esteem (r = .102), indicating conceptual independence of these two constructs. Effects were stronger when the B-algorithm was used for calculation of IPT-scores and the IPT was administered only once, whilst all other moderators did not show significant influences. Regression analyses revealed a somewhat stronger (albeit non-significant) effect for men. Moreover, there was no evidence for dissemination bias or a decline effect, although effects from published studies were numerically somewhat stronger than unpublished effects. Discussion: We show that there is no noteworthy association between IPT-based implicit and explicit self-esteem, which is broadly consistent with dual-process models of implicit and explicit evaluations on the one hand, but also casts doubt on the suitability of the IPT for the assessment of implicit self-esteem on the other hand. [ABSTRACT FROM AUTHOR]

Humor and mental health are interconnected as is evidenced by a large number of studies. However, associations are only small and inconsistent as the operationalization of humor poses a methodological challenge. The Humor Styles Questionnaire (HSQ) differentiates four humor styles that might be beneficial or harmful to mental health. The aim of the present study was to meta‐analytically aggregate studies using the HSQ to assess the associations of different humor styles with four areas of mental health (self‐esteem, life satisfaction, optimism, depression). An extensive electronic database literature search identified 37 studies that reported correlations between the HSQ scales and the four areas of mental health in 45 independent samples (total N = 12,734). In total, 16 meta‐analyses were conducted. Moderating effects of participant age, sex, and geographic region were examined via subgroup analyses and meta‐regression. Humor styles differed in terms of their associations with mental health. Health‐promoting humor styles were overall positively correlated with mental health (small‐to‐medium effect sizes). Self‐defeating humor was overall negatively correlated with mental health. Aggressive humor was overall unrelated with mental health. Moderator analyses suggested geographic differences (Eastern vs. Western samples) and sex differences for some of these associations. Fostering specific humor styles may be beneficial for mental health. In addition, observing the habitual use of humor styles might help therapists to develop a better understanding of their clients. Differences in the utilization and the correlates of humor styles in Eastern and Western societies, and sex differences, need to be addressed in future research. [ABSTRACT FROM AUTHOR]

The Flynn effect (rising intelligence test performance in the general population over time and generations) varies enigmatically across countries and intelligence domains; its substantive meaning and causes remain elusive. This first formal meta-analysis on the topic revealed worldwide IQ gains across more than one century (1909–2013), based on 271 independent samples, totaling almost 4 million participants, from 31 countries. Key findings include that IQ gains vary according to domain (estimated 0.41, 0.30, 0.28, and 0.21 IQ points annually for fluid, spatial, full-scale, and crystallized IQ test performance, respectively), are stronger for adults than children, and have decreased in more recent decades. Altogether, these findings narrow down proposed theories and candidate factors presumably accounting for the Flynn effect. Factors associated with life history speed seem mainly responsible for the Flynn effect’s general trajectory, whereas favorable social multiplier effects and effects related to economic prosperity appear to be responsible for observed differences of the Flynn effect across intelligence domains. [ABSTRACT FROM AUTHOR]

Research has shown that forest plots are a gold standard in the visualization of meta-analytic results. However, research on the general interpretation of forest plots and the role of researchers' meta-analysis experience and field of study is still unavailable. Additionally, the traditional display of effect sizes, confidence intervals, and weights have repeatedly been criticized. The current work presents an online statistical cognition experiment in which a total of 279 researchers with experience in meta-analysis from 36 countries evaluated conventional forest plots and two novel versions of forest plots, namely, thick forest plots and rainforest plots. The results indicate certain biases in the interpretation of forest plots, especially with regard to heterogeneity, the distribution of weights, and the theoretical concept of confidence intervals. Although the two novel displays (thick forest plots and rainforest plots) are associated with slightly longer viewing times, they are at least as well-suited and esthetically and perceptively pleasing as the conventional displays while facilitating the correct and exhaustive interpretation of the meta-analytic information. Furthermore, it is advisable to combine conventional forest plots with distribution information of the individual effects, make confidence lines more visually striking, and to display a background grid in the graph. Copyright © 2014 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

Research from various countries consistently reported an advantage of boys over girls in general knowledge and was also suggestive of some overall trends regarding specific domains of general knowledge that were speculated to stem from biologically differentiated interests. However, results were heterogeneous and, as of yet, had not been evaluated meta-analytically. Moreover, previous research drew on overly homogeneous high-school or undergraduate samples whose representativeness appears problematic; mostly, likely moderators, such as school type, student age or parental education, were also not directly investigated or controlled for. We provide a meta-analytical aggregation of available results regarding sex differences in general knowledge and present new data, investigating the psychometric properties of the General Knowledge Test (GKT), on which previous research primarily relied, and explored sex differences in a large and heterogeneous Austrian high-school student sample (N = 1088). The aggregated sex effect in general knowledge was of medium size in previous research, but differences in specific domains were heterogeneous across countries and only modest at best. Large sex differences in our data could be explained to a large part by school-related moderators (school type, school, student age, parental education) and selection processes. Boys had a remaining advantage over girls that was only small in size and that was consistent with the magnitude of sex differences in general intelligence. Analysis of the GKT yielded no evidence of biologically differentiated interests, but of a specific interest in the humanities among girls. In conclusion, previous research likely overestimated sex differences in general knowledge. [ABSTRACT FROM AUTHOR]

Graphs are an essential part of scientific communication. Complex datasets, of which meta-analyses are textbook examples, benefit the most from visualization. Although a number of graph options for meta-analyses exist, the extent to which these are used was hitherto unclear. A systematic review on graph use in meta-analyses in three disciplines (medicine, psychology, and business) and nine journals was conducted. Interdisciplinary differences, which are mirrored in the respective journals, were revealed, that is, graph use correlates with external factors rather than methodological considerations. There was only limited variation in graph types (with forest plots as the most important representatives), and diagnostic plots were very rare. Although an increase in graph use over time could be observed, it is unlikely that this phenomenon is specific to meta-analyses. There is a gaping discrepancy between available graphic methods and their application in meta-analyses. This may be rooted in a number of factors, namely, (i) insufficient dissemination of new developments, (ii) unsatisfactory implementation in software packages, and (iii) minor attention on graphics in meta-analysis reporting guidelines. Using visualization methods to their full capacity is a further step in using meta-analysis to its full potential. Copyright © 2013 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

Individuals like their name letters more than non-name letters. This effect has been termed the Name Letter Effect (NLE) and is widely exploited to measure implicit (i.e. automatic, unconscious) self-esteem, predominantly by means of the Initial Preference Task (IPT). Methodological research on how to best administer the IPT is, however, scarce. In order to bridge this gap, the present paper assessed the advantages and disadvantages of different types of IPT administrations with two meta-analyses ( k = 49; N = 11,514) and a follow-up experiment ( N = 449). As a result, a new type of administration is recommended which (1) treats the effects of the first and the last name initials separately, (2) uses a duplicate administration for reliability reasons, (3) uses the likability as well as the attractiveness item wording and (4) exploits not only letters but also numbers (i.e. birthday number effect) to measure implicit self-esteem. Copyright © 2011 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

Abstract: Three new studies (N= 132, 623, 1112) did not yield hypothesized associations between digit ratio (2D:4D), an assumed negative correlate of prenatal testosterone, and psychometrically measured sex-role orientation (positive association with femininity, negative ones with masculinity and masculinity-femininity difference scores) among heterosexuals of either sex. Meta-analysis of the pertinent literature (N= 6311, 28 studies from 10 countries, 46% unpublished) showed only men’s (but not women’s) left-hand (but not right-hand) 2D:4D reliably related as expected (positively) to femininity. This effect was tiny (0.14% attributable variance) and possibly non-robust (crucially dependent on one large study included). Hence, the cumulative evidence does not support systematic, robust, noteworthy within-sex correlations between 2D:4D and the masculinity/femininity personality dimensions. [Copyright &y& Elsevier]

Background: Generational IQ gains in the general population (termed the Flynn effect) show an erratic pattern across different nations as well as across different domains of intelligence (fluid vs crystallized). Gains of fluid intelligence in different countries have been subject to extensive research, but less attention was directed towards gains of crystallized intelligence, probably due to evidence from the Anglo-American sphere suggesting only slight gains on this measure. In the present study, development of crystallized intelligence in the German speaking general population is assessed. Methodology/Principal Findings: To investigate whether IQ gains for crystallized intelligence are in progress in Germanspeaking countries, two independent meta-analyses were performed. By means of a cited reference search in ISI Web of Science, all studies citing test manuals and review articles of two widely-used salient measures of crystallized intelligence were obtained. Additionally, the electronic database for German academic theses was searched to identify unpublished studies employing these tests. All studies reporting participants mean IQ or raw scores of at least one of the two measures were included in the present analyses, yielding over 500 studies (>1,000 samples; >45,000 individuals). We found a significant positive association between years of test performance and intelligence (1971-2007) amounting to about 3.5 IQ points per decade. Conclusions/Significance: This study clearly demonstrates that crystallized IQ gains are substantial and of comparable strength as Flynn effects typically observed for measures of fluid intelligence in Central Europe. Since mean IQ was assessed in a large number of small, non-representative samples, our evidence suggests a remarkable robustness of these gains. Moreover, in both meta-analyses strength of gains was virtually identical. On the whole, results of the present study demonstrate a pervasive and generalizing Flynn effect in German-speaking countries. [ABSTRACT FROM AUTHOR]

Abstract: The transient enhancement of performance on spatial tasks in standardized tests after exposure to the first movement “allegro con spirito” of the Mozart sonata for two pianos in D major (KV 448) is referred to as the Mozart effect since its first observation by . These findings turned out to be amazingly hard to replicate, thus leading to an abundance of conflicting results. Sixteen years after initial publication we conduct the so far largest, most comprehensive, and up-to-date meta-analysis (nearly 40 studies, over 3000 subjects), including a diversity of unpublished research papers to finally clarify the scientific record about whether or not a specific Mozart effect exists. We could show that the overall estimated effect is small in size (d =0.37, 95% CI [0.23, 0.52]) for samples exposed to the Mozart sonata KV 448 and samples that had been exposed to a non-musical stimulus or no stimulus at all preceding spatial task performance. Additionally, calculation of effect sizes for samples exposed to any other musical stimulus and samples exposed to a non-musical stimulus or no stimulus at all yielded effects similar in strength (d =0.38, 95% CI [0.13, 0.63]), whereas there was a negligible effect between the two music conditions (d =0.15, 95% CI [0.02, 0.28]). Furthermore, formal tests yielded evidence for confounding publication bias, requiring downward correction of effects. The central finding of the present paper however, is certainly the noticeably higher overall effect in studies performed by Rauscher and colleagues than in studies performed by other researchers, indicating systematically moderating effects of lab affiliation. On the whole, there is little evidence left for a specific, performance-enhancing Mozart effect. [Copyright &y& Elsevier]

Abstract: Previously reported associations between low (male-typical) digit ratio (2D:4D), a putative pointer to prenatal testosterone exposure, and high (male-typical) sensation seeking have been inconsistent across studies (alternately present for men, women, either sex, or neither). Addressing this question again in three new studies (N =198, 188, 1118) produced similarly erratic findings. Meta-analysis of the entire literature (13 studies with nearly 3000 individuals, including unpublished accounts) showed that the current cumulative evidence does not support any negative correlations between 2D:4D and sensation seeking traits. The only significant meta-analytical finding was for right-hand 2D:4D and the experience seeking facet of sensation seeking in both sexes, but this effect accounted for merely 0.4% attributable variance, and moreover was directionally opposite to expectation (i.e., a positive correlation). Discussed are inherent limitations of narrow-scoped approaches (such as via 2D:4D) for elucidating the biological bases of individual difference variables with evidentially intricate neurochemical underpinnings (such as sensation seeking). [Copyright &y& Elsevier]

A scientometric analysis of modern research on the second-to-fourth digit ratio (2D:4D), a widely studied putative marker for prenatal androgen action, is presented. In early 2009, this literature totalled more than 300 publications and, since its initiation in 1998, has grown at a rate slightly faster than linear. Key findings included evidence of publication bias and citation bias, incomplete coverage and outdatedness of existing reviews, and a dearth of meta-analyses in this field. 2D:4D research clusters noticeably in terms of researchers, institutions, countries, and journals involved. Although 2D:4D is an anthropometric trait, most of the research has been conducted at psychology departments, not anthropology departments. However, 2D:4D research has not been predominantly published in core and specialized journals of psychology, but rather in more broadly scoped journals of the behavioral sciences, biomedical social sciences, and neurosciences. Total citation numbers of 2D:4D papers for the most part were not larger than their citation counts within 2D:4D research, indicating that until now, only a few 2D:4D studies have attained broader interest outside this specific field. Comparative citation analyses show that 2D:4D research presently is commensurate in size and importance to evolutionary psychological jealousy research, but has grown faster than the latter field. In contrast, it is much smaller and has spread more slowly than research about the Implicit Association Test. Fifteen conjectures about anticipated trends in 2D:4D research are outlined, appendixed by a first-time bibliography of the entirety of the published 2D:4D literature. [ABSTRACT FROM AUTHOR]

Nonpaternity (i.e., discrepant biological versus social fatherhood) affects many issues of interests to psychologists, including familial dynamics, interpersonal relationships, sexuality, and fertility, and therefore represents an important topic for psychological research. The advent of modern contraceptive methods, particularly the market launch of the birth-control pill in the early 1960s and its increased use ever since, should have affected rates of nonpaternity (i.e., discrepant genetic and social fatherhood). This cross-temporal mets-analysis investigated whether there has been a recent decline in nonpaternity rates in the western industrialized nations. The eligible database comprised 32 published samples unbiased towards nonpaternity for which nonoverlapping data from more than 24,000 subjects from nine (mostly Anglo-Saxon heritage) countries with primarily Caucasian populations are reported. Publication years ranged from 1932 to 1999, and estimated years of the reported nonpaternity events (i.e., the temporal occurrence of nonpaternity) ranged from 1895 to 1993. In support of the hypothesis, weighted meta-regression models showed a significant decrease (r=-.4 1) of log-transformed nonpaternity rates with publication years and also a decrease, albeit not significant (r=-.17), with estimated years of nonpaternity events. These results transform into an estimated absolute decline in untransformed nonpaternity rates of 0.83% and 0.91% per decade, respectively. Across studies, the mean (and median) nonpaternity rate was 3.1% (2.1%). This estimate is consistent with estimates of 2 to 3% from recent reviews on the topic that were based on fewer primary studies. This estimate also rebuts the beliefs and hearsay data widespread among both the public and researchers which contend nonpaternity rates in modern populations might be as high as about 10%. [ABSTRACT FROM AUTHOR]

Since the emergence of twin studies in the 1920s, time and again the question of possible twin-singleton differences in intelligence has been posed. This study addressed the issue through a meta-analyais of published studies on this theme. Twins on the average seem to have lower IQs than singletons. The best estimate for this group difference is 4.2 IQ points (less than one-third of a standard deviation), with a great divide between study outcomes of less vs more recent birth cohorts (5.1 vs 05 IQ points, respectively). The evidence is based on studies from six countries (including population-based ones of entire birth cohorts), a massive database (comparisons of more than 30,000 twins with nearly 1.6 million singletons), a variety of intelligence tests, and birth cohorts spanning most of the 20th century, but, for the most part, on an age range limited to children and adolescents. The effect shows considerable between-study heterogeneity but appears robust (fail-safe N calculations), not due to influential individual studies (sensitivity analysis) or publication bias, was present since the very first published studies (cumulative meta-analysis), and appears generaliz. able across sex, zygosity, and other intelligence domains beyond the verbal. There are insufficient data as to whether the effect persists over the lifespan, exists as well within families, or has ceased in recent birth cohorts of highly developed countries (Denmark and The Netherlands). Likely causes of the effect appear to be prenatal and peri-natal factors (reduced fetal growth and shorter gestation for twins). [ABSTRACT FROM AUTHOR]

The objectives of this review were to examine the overall efficacy of music therapy for children and adolescents with psychopathology, and to examine how the size of the effect of music therapy is influenced by the type of pathology, client's age, music therapy approach, and type of outcome. Eleven studies were included for analysis, which resulted in a total of 188 subjects for the meta-analysis. Effect sizes from these studies were combined, with weighting for sample size, and their distribution was examined. After exclusion of an extreme positive outlying value, the analysis revealed that music therapy has a medium to large positive effect (ES = .61) on clinically relevant outcomes that was statistically highly significant ( p < .001) and statistically homogeneous. No evidence of a publication bias was identified. Effects tended to be greater for behavioural and developmental disorders than for emotional disorders; greater for eclectic, psychodynamic, and humanistic approaches than for behavioural models; and greater for behavioural and developmental outcomes than for social skills and self-concept. Implications for clinical practice and research are discussed. [ABSTRACT FROM AUTHOR]

A series of meta-analyses assessed whether differentially efficacious variants (CAG and GGC repeat-length polymorphisms) of the human androgen receptor gene are associated with digit ratio (2D:4D), a widely investigated putative pointer to prenatal androgen action. Extensive literature search strategies identified a maximum of 18 samples (total N = 2909) vs. 5 samples (N = 1497) for the CAG-related vs. GGC-related meta-analyses, respectively. In contrast to a small-sample (N = 50) initial report, widely cited affirmatively in the literature, meta-analysis of the entire retrievable evidence base did not support any associations between CAG variants and right-hand, left-hand, or right-minus-left-hand 2D:4D. Effects of GGC variants on digit ratios likewise were almost exactly null. For the CAG literature, time trend analysis indicated shrinking effects among more recent studies. Both quantitative and qualitative citation analyses documented that citation bias exists in the research literature: CAG-related studies yielding larger effects were cited more frequently within the same time unit, and the initial, unreplicated report continued to be cited frequently and mostly solely as well as confirmatively, while non-replications were cited much less often. The meta-analytical null findings, along with several further strands of evidence consistent with these, undermine one validity claim for 2D:4D as a retrospective pointer to prenatal testosterone action. Discussed are alternative interpretations of the evidence and avenues for future research. [ABSTRACT FROM AUTHOR]

Positive associations between human intelligence and brain size have been suspected for more than 150 years. Nowadays, modern non-invasive measures of in vivo brain volume (Magnetic Resonance Imaging) make it possible to reliably assess associations with IQ. By means of a systematic review of published studies and unpublished results obtained by personal communications with researchers, we identified 88 studies examining effect sizes of 148 healthy and clinical mixed-sex samples (>8000 individuals). Our results showed significant positive associations of brain volume and IQ ( r = .24, R 2 = .06) that generalize over age (children vs. adults), IQ domain (full-scale, performance, and verbal IQ), and sex. Application of a number of methods for detection of publication bias indicates that strong and positive correlation coefficients have been reported frequently in the literature whilst small and non-significant associations appear to have been often omitted from reports. We show that the strength of the positive association of brain volume and IQ has been overestimated in the literature, but remains robust even when accounting for different types of dissemination bias, although reported effects have been declining over time. While it is tempting to interpret this association in the context of human cognitive evolution and species differences in brain size and cognitive ability, we show that it is not warranted to interpret brain size as an isomorphic proxy of human intelligence differences. [ABSTRACT FROM AUTHOR]

Abstract: The large number of published meta-analyses on the associations between single-nucleotide polymorphisms (SNPs) and suicidal behavior mirrors the enormous research interest in this topic. Although meta-analytic evidence is abundant and certain patterns are apparent, those have not been integrated into a general framework as of yet. In a systematic review, genetic association studies between SNPs and suicidal behavior were identified. Previously published meta-analyses for eight SNPs were updated and the results of the different meta-analyses were compared. Meta-analyses for 15 SNPs, which had not been subjected to meta-analysis before, were conducted. The present meta-analytical field synopsis showed five major similarities between new and published analyses: 1) Summary effect sizes were small and rarely statistically significant, 2) heterogeneity between studies was often substantial, 3) there were no time trends, 4) effects were easily swayed and were largely dependent on individual studies, and 5) publication bias does not play a role in this field of research. Meta-analytic data show once more that major contributions of single genes are unlikely. However, association studies and corresponding meta-analyses have been an important and necessary stepping stone in the development of modern and more complex approaches in the genetics of suicidal behavior. [Copyright &y& Elsevier]