Assessing the association between parents' math talk and children's math performance: A preregistered meta-analysis

The home math environment has gained considerable attention as a potential cause of variation in children's math performance, and recent research has suggested positive associations between parents' math talk and children's mathematical performance. However, the extent to which associations reflect robust causal effects is difficult to test. In a preregistered meta-analysis, we assess the association between parents' math talk and children's math performance. Our initial search identified 24,291 potential articles. After screening, we identified 22 studies that were included in analyses (k = 280 effect sizes, n = 35,917 participants). A multilevel random effects meta-analysis was employed, finding that parents' math talk is significantly associated with children's math performance (b = 0.10, SE = 0.03, p = .002). We tested whether associations differ as a function of sample characteristics, observation context, observation length, type of math talk and math performance measured, and modeling approaches to math talk variable analysis. In addition, we tested whether associations are robust to the inclusion of strong baseline covariates and found that effects attenuated when children's domain-general and/or prior math abilities are included. We discuss plausible bounds of the effects of parents' math talk on children's mathematical performance to inform power analyses and experimental work on the impact of parents' math language on children's math learning.

Fraction Ball impact on student and teacher math talk and behavior

We assessed the impacts of Fraction Ball-a novel suite of games combining the benefits of embodied guided play for math learning-on the math language production and behavior of students and teachers. In the Pilot Experiment, 69 fifth and sixth graders were randomly assigned to play four different Fraction Ball games or attend normal physical education class. The Efficacy Experiment was implemented to test improvements made through co-design with teachers with 160 fourth through sixth graders. Researchers observed and coded for use of math language and behavior. Playing Fraction Ball resulted in consistent increases of students' and teachers' use of fraction (SDs = 0.98-2.42) and decimal (SDs = 0.65-1.64) language and number line arithmetic, but not in whole number, spatial language, counting, instructional gesturing, questioning, and planning. We present evidence of the math language production in physical education and value added by Fraction Ball to support rational number language and arithmetic through group collaboration.

Effects of homicide timing on test scores: Quasi-experimental evidence from two cities in Colombia

This study examines the effect of homicides around schools on the standardized test scores of fifth and ninth graders (N = 4729; Mage  = 12.71 years, SDage  = 2.13) using a quasi-experimental design in two Colombian cities. Exposure to homicides occurring within 7 days of the test and within 500 m of the school decreases test scores by 0.10 SD. Effects show a greater sensitivity to timing than distance, becoming null as the time to the testing date increases but remaining consistent across larger radii. Since students in the study are on average exposed to 12.1 homicides per year, even short-lived learning losses can accumulate to impair learning for substantial portions of the school year. Findings are discussed, considering previous empirical work.

Girls' comparative advantage in language arts explains little of the gender gap in math-related fields: A replication and extension

Women remain underrepresented in most math-intensive fields. [Breda and Napp, Proc. Natl. Acad. Sci. U.S.A. 116, 15435 (2019)] reported that girls' comparative advantage in reading over math (i.e., the intraindividual differences between girls' reading vs. math performance, compared to such differences for boys) could explain up to 80% of the gender gap in students' intentions to pursue math-intensive studies and careers, in conflict with findings from previous research. We conducted a conceptual replication and expanded upon Breda and Napp's study by using new global data (PISA2018, N = 466,165) and a recent US nationally representative longitudinal study (High School Longitudinal Study of 2009, N = 6,560). We coded students' intended majors and careers and their actual college majors. The difference between a student's math vs. reading performance explained only small proportions of the gender gap in students' intentions to pursue math-intensive fields (0.4 to 10.2%) and in their enrollment in math-intensive college majors (12.3%). Consistent with previous studies, our findings suggest girls' comparative advantage in reading explains a minority of the gender gap in math-related majors and occupational intentions and choices. Potential reasons for differences in the estimated effect sizes include differences in the operationalization of math-related choices, the operationalization of math and reading performance, and possibly the timing of measuring intentions and choices. Therefore, it seems premature to conclude that girls' comparative advantage in reading, rather than the cumulative effects of other structural and/or psychological factors, can largely explain the persistent gender gap in math-intensive educational and career choices.

Triangulating on developmental models with a combination of experimental and nonexperimental estimates

Plausible competing developmental models show similar or identical structural equation modeling model fit indices, despite making very different causal predictions. One way to help address this problem is incorporating outside information into selecting among models. This study attempted to select among developmental models of children's early mathematical skills by incorporating information about the extent to which models forecast the longitudinal pattern of causal impacts of early math interventions. We tested for the usefulness and validity of the approach by applying it to data from three randomized controlled trials of early math interventions with longitudinal follow-up assessments in the United States (Ns = 1,375, 591, 744; baseline age 4.3, 6.5, 4.4; 17%-69% Black). We found that, across data sets, (a) some models consistently outperformed other models at forecasting later experimental impacts, (b) traditional statistical fit indices were not strongly related to causal fit as indexed by models' accuracy at forecasting later experimental impacts, and (c) models showed consistent patterns of similarity and discrepancy between statistical fit and models' effectiveness at forecasting experimental impacts. We highlight the importance of triangulation and call for more comparisons of experimental and nonexperimental estimates for choosing among developmental models. (PsycInfo Database Record (c) 2023 APA, all rights reserved).

Developmental changes in students' use of dimensional comparisons to form ability self-concepts in math and verbal domains

Dimensional comparisons (i.e., comparing own performances across domains) may drive an increasing differentiation in students' math and verbal self-concepts over time, but little longitudinal research has directly tested this assumption. Using cross-sequential data spanning Grades 1-12 (N = 1069, ages 6-18, 92% White, 2% Black, 51% female, collected 1987-1996), this study charted age-related changes in the role of dimensional comparisons in students' ability self-concept formation. It used three types of self-concept measures: peer comparisons, cross-domain comparisons, and no comparisons. Results indicated that the increase in students' use of dimensional comparisons in self-evaluations substantially contributed to the increasing differentiation in students' math and verbal self-concepts over time. Findings highlight the importance of dimensional comparisons in the development of students' ability self-concepts.

Design and Analytic Features for Reducing Biases in Skill-Building Intervention Impact Forecasts

Despite policy relevance, longer-term evaluations of educational interventions are relatively rare. A common approach to this problem has been to rely on longitudinal research to determine targets for intervention by looking at the correlation between children's early skills (e.g., preschool numeracy) and medium-term outcomes (e.g., first-grade math achievement). However, this approach has sometimes over-or under-predicted the long-term effects (e.g., 5th-grade math achievement) of successfully improving early math skills. Using a within-study comparison design, we assess various approaches to forecasting medium-term impacts of early math skill-building interventions. The most accurate forecasts were obtained when including comprehensive baseline controls and using a combination of conceptually proximal and distal short-term outcomes (in the nonexperimental longitudinal data). Researchers can use our approach to establish a set of designs and analyses to predict the impacts of their interventions up to two years post-treatment. The approach can also be applied to power analyses, model checking, and theory revisions to understand mechanisms contributing to medium-term outcomes.

Shared and unique affective abnormalities in schizotypy dimensions

Attention to affect is theoretically a precursor to one's ideal affect (i.e., preference for feeling low- and high-arousal positive and negative affect) and emotion regulation (ER). In schizotypy, there have been mixed findings regarding abnormalities in attention to affect. At the same time, little is known about ideal affect in schizotypy or whether differences in ideal affect or ER difficulties in schizotypy are driven by attention to affect. Thus, this study aimed to identify shared and unique abnormalities in attention to affect, ideal affect, and ER difficulties in schizotypy, and to test whether attention to affect underlies differences in ideal affect and ER difficulties. Using groups of individuals with either extreme levels of social anhedonia (SocAnh; n = 181), extreme levels of perceptual aberrations/magical ideation (PerMag; n = 105), or individuals low on both (i.e., controls; n = 531), we tested group differences in attention to affect, ideal affect, and ER difficulties. Our findings suggest both shared and unique affective abnormalities; compared to controls, the SocAnh group paid the least attention to positive affect. Only PerMag had heightened attention to negative affect compared to controls. Additionally, we found unique abnormalities relating to ideal affect but mostly shared difficulties in ER in schizotypy. Abnormalities in ideal affect and ER remain largely consistent after accounting for attention to affect for PerMag, suggesting that attention to affect is not the primary mechanism driving these abnormalities. However, we found evidence that attention to affect underlies some SocAnh-control group differences in ideal affect and ER difficulties. Our work helps to clarify prior work and contributes to the understanding of shared and unique affective abnormalities in schizotypy. Future research may consider longitudinal approaches to test causal mechanisms of affective abnormalities in schizotypy.

A multilevel meta-analysis on the causal effect of approximate number system training on symbolic math performance

We performed a meta-analysis of approximate number system (ANS) training studies to investigate the strength of the causal effects of practicing ANS related tasks on symbolic math performance. Across 33 effect sizes from 11 studies involving 754 participants, for which neither the treatment nor control group received symbolic training, we found a small nonsignificant and sensitive effect of ANS training on symbolic math task performance (g = .11, 95% confidence interval, CI [-.01, .22]; precision-effect estimate with standard errors (PEESE) adjusted g = -.04, 95% CI [-.58, .50]). Some heterogeneity was accounted for by participant age, with larger estimates for adults than for children. Estimates did not vary significantly by ANS training type, training duration, and control group type. An exploratory analysis on the transfer effects of ANS training on untrained nonsymbolic tasks suggests weak support for the key auxiliary assumption that ANS training has substantial effects on a general ANS, indicating that the training literature may not adequately represent theories of how ANS influences symbolic number performance. (PsycInfo Database Record (c) 2021 APA, all rights reserved).

Persistence and Fade-Out of Educational-Intervention Effects: Mechanisms and Potential Solutions

Some environmental influences, including intentional interventions, have shown persistent effects on psychological characteristics and other socially important outcomes years and even decades later. At the same time, it is common to find that the effects of life events or interventions diminish and even disappear completely, a phenomenon known as fadeout. We review the evidence for persistence and fadeout, drawing primarily on evidence from educational interventions. We conclude that 1) fadeout is widespread, and often co-exists with persistence; 2) fadeout is a substantive phenomenon, not merely a measurement artefact; and 3) persistence depends on the types of skills targeted, the institutional constraints and opportunities within the social context, and complementarities between interventions and subsequent environmental affordances. We discuss the implications of these conclusions for research and policy.

Rock the MIC: The Matrix of Implied Causation, a Tool for Experimental Design and Model Checking

Path modeling and the extended structural equation modeling framework are in increasingly common use for statistical analysis in modern behavioral science. Path modeling, including structural equation modeling, provides a flexible means of defining complex models in a way that allows them to be easily visualized, specified, and fitted to data. Although causality cannot be determined simply by fitting a path model, researchers often use such models as representations of underlying causal-process models. Indeed, causal implications are a vital characteristic of a model’s explanatory value, but these implications are rarely examined directly. When models are hypothesized to be causal, they can be differentiated from one another by examining their causal implications as defined by a combination of the model assumptions, data, and estimation procedure. However, the implied causal relationships may not be immediately obvious to researchers, especially for intricate or long-chain causal structures (as in longitudinal panel designs). We introduce the matrix of implied causation (MIC) as a tool for easily understanding and reporting a model’s implications for the causal influence of one variable on another. With examples from the literature, we illustrate the use of MICs in model checking and experimental design. We argue that MICs should become a routine element of interpretation when models with complex causal implications are examined, and that they may provide an additional tool for differentiating among models with otherwise similar fit.

Reciprocal effects of reading and mathematics? Beyond the cross-lagged panel model

Prior nonexperimental studies have been used to conclude that children's reading and mathematics achievement bidirectionally influence each other over time, with strong paths from (a) early reading to later mathematics and (b) early mathematics to later reading. In the most influential study on the topic, the early math-to-later-reading path was reported to be stronger than the early reading-to-later-math path (Duncan et al., 2007). Yet prior estimates may be confounded by stable environmental and personal factors influencing both reading and mathematics achievement. We reexamined the bidirectional relations between reading and mathematics achievement using both traditional models and extensions intended to account for unmeasured confounding. Results based on a large nationally representative sample of children from kindergarten to 3rd grade (N = 9,612) indicated that the estimated effects between reading and mathematics achievement differ substantially after accounting for the confounding effects of stable unmeasured factors. In these models, autoregressive and cross-lagged paths were substantially reduced. The finding that early mathematics predicts later reading more strongly than early reading predicts later math disappears and sometimes reverses, suggesting that larger paths from math to reading than from reading to math in previous related analyses are not causally informative. Stability in early mathematics and reading achievement resulted from substantially overlapping time invariant factors that correlate above .90. (PsycInfo Database Record (c) 2020 APA, all rights reserved).

Dual-task studies of working memory and arithmetic performance: A meta-analysis

We performed a meta-analysis of dual-task experiments to assess the robustness of the effects of conducting working memory secondary tasks on arithmetic performance. Four hundred effect sizes from 21 studies from 1,049 participants were analyzed across a variety of specifications. Results revealed that increases in working memory load resulted in slower (7% to 19% reduction) speed of solving of arithmetic problems. Of the potential moderators, working memory load type (i.e., central executive, phonological loop, and visuospatial sketchpad), arithmetic task type (e.g., addition verification, approximate addition, exact multiplication), and authors' predictions for significance which served as a proxy for cross-talk were statistically significant across specifications, but participants' age was not. Working memory load type was the most substantial moderator, with central executive tasks leading to the greatest slowing of performance, suggesting that the cognitive complexity of a working memory task may exert a larger influence on performance than the domain-specific overlapping processing demands of similar tasks. We discuss the apparent discrepancy between these findings and findings from correlational studies of the relation between arithmetic performance and working memory, which have reported similar correlations across working memory domains, on average. (PsycInfo Database Record (c) 2021 APA, all rights reserved).

Late electrophysiological potentials and emotion in schizophrenia: A meta-analytic review

INTRODUCTION

There is mixed evidence about emotional processing abnormalities in schizophrenia and schizoaffective disorder, with self-reports and clinician ratings indicating significant differences between patients and controls, but studies of in-the-moment, self-reported emotional experience finding only small differences between these groups. The current meta-analysis synthesizes statistics from studies measuring the P3 and LPP, two event-related potential (ERP) components sensitive to attentional allocation, to examine whether patients exhibit ERP response abnormalities to neutral and valenced visual stimuli.

METHODS

Standardized mean amplitudes and standard errors of P3 and/or LPP waveforms (300-2000 ms) in response to neutral and valenced images were calculated for 13 studies (total n = 339 individuals with schizophrenia, 331 healthy controls).

RESULTS

In response to neutral images, there were very small, non-significant differences in ERP amplitudes between patient and control groups (k = 9; Hedges' g = -0.06, 95% CI: -055, 0.43, p = 0.81). In contrast, patients showed a small, significant reduction in ERP amplitudes compared to controls in response to negative images (k = 13; Hedges' g = -0.32, 95% CI: -0.59, -0.05, p = 0.02) and a small, but nonsignificant, reduction in amplitudes in response to positive images (k = 7; Hedges' g = -0.27, 95% CI: -0.71, 0.18, p = 0.24).

CONCLUSIONS AND IMPLICATIONS

The current review indicates that compared to controls, patients have slightly diminished P3 and LPP amplitudes in response to positive and negative stimuli. This small reduction may reflect decreased attention allocation, possibly indicating an abnormality during a distinct stage of early processing related to evaluating the motivational salience of a stimulus.

Theoretical and Methodological Implications of Associations between Executive Function and Mathematics in Early Childhood

Despite agreement about the importance of executive function (EF) for children's early math achievement, its treatment in correlational studies reflects a lack of agreement about the theoretical connection between the two. It remains unclear whether the association between EF and math operates through a latent EF construct or specific EF components. Specifying the correct measurement model has important theoretical implications for the predicted effects of EF interventions on children's math achievement. In the current study, we tested whether associations between EF and math operate via a latent EF factor, or via specific EF components using data from a large, nationally representative sample. We then replicated these same analyses with a meta-analytic database drawn from ten studies that collected measures of children's EF and math achievement. Our results lend support to explanations that a single EF factor accounts for most of the EF component-specific associations with math achievement. We discuss theoretical and methodological implications of these findings for future work.

The Roles of Transfer of Learning and Forgetting in the Persistence and Fadeout of Early Childhood Mathematics Interventions

Although many interventions have generated immediate positive effects on mathematics achievement, these effects often diminish over time, leading to the important question of what causes fadeout and persistence of intervention effects. This study investigates how children's forgetting contributes to fadeout and how transfer contributes to the persistence of effects of early childhood mathematics interventions. We also test whether having a sustaining classroom environment following an intervention helps mitigate forgetting and promotes new learning. Students who received the intervention we studied forgot more in the following year than students who did not, but forgetting accounted for only about one-quarter of the fadeout effect. An offsetting but small and statistically non-significant transfer effect accounted for some of the persistence of the intervention effect - approximately one-tenth of the end-of-program treatment effect and a quarter of the treatment effect one year later. These findings suggest that most of the fadeout was attributable to control-group students catching up to the treatment-group students in the year following the intervention. Finding ways to facilitate more transfer of learning in subsequent schooling could improve the persistence of early intervention effects.

Prevention: Necessary But Insufficient? A 2-Year Follow-Up of an Effective First-Grade Mathematics Intervention

We present first-grade, second-grade, and third-grade impacts for a first-grade intervention targeting the conceptual and procedural bases that support arithmetic. At-risk students (average age at pretest = 6.5) were randomly assigned to three conditions: a control group (n = 224) and two variants of the intervention (same conceptual instruction but different forms of practice: speeded [n = 211] vs. nonspeeded [n = 204]). Impacts on all first-grade content outcomes were significant and positive, but no follow-up impacts were significant. Many intervention children achieved average mathematics achievement at the end of third grade, and prior math and reading assessment performance predicted which students will require sustained intervention. Finally, projecting impacts 2 years later based on nonexperimental estimates of effects of first-grade math skills overestimates long-term intervention effects.

Risky business: Correlation and causation in longitudinal studies of skill development

Developmental theories often posit that changes in children's early psychological characteristics will affect much later psychological, social, and economic outcomes. However, tests of these theories frequently yield results that are consistent with plausible alternative theories that posit a much smaller causal role for earlier levels of these psychological characteristics. Our article explores this issue with empirical tests of skill-building theories, which predict that early boosts to simpler skills (e.g., numeracy or literacy) or behaviors (e.g., antisocial behavior or executive functions) support the long-term development of more sophisticated skills or behaviors. Substantial longitudinal associations between academic or socioemotional skills measured early and then later in childhood or adolescence are often taken as support of these skill-building processes. Using the example of skill-building in mathematics, we argue that longitudinal correlations, even if adjusted for an extensive set of baseline covariates, constitute an insufficiently risky test of skill-building theories. We first show that experimental manipulation of early math skills generates much smaller effects on later math achievement than the nonexperimental literature has suggested. We then conduct falsification tests that show puzzlingly high cross-domain associations between early math and later literacy achievement. Finally, we show that a skill-building model positing a combination of unmeasured stable factors and skill-building processes can reproduce the pattern of experimental impacts on children's mathematics achievement. Implications for developmental theories, methods, and practice are discussed. (PsycINFO Database Record

Does Reading Cause Later Intelligence? Accounting for Stability in Models of Change

This study reanalyzes data presented by Ritchie, Bates, and Plomin (2015) who used a cross-lagged monozygotic twin differences design to test whether reading ability caused changes in intelligence. The authors used data from a sample of 1,890 monozygotic twin pairs tested on reading ability and intelligence at five occasions between the ages of 7 and 16, regressing twin differences in intelligence on twin differences in prior intelligence and twin differences in prior reading ability. Results from a state-trait model suggest that reported effects of reading ability on later intelligence may be artifacts of previously uncontrolled factors, both environmental in origin and stable during this developmental period, influencing both constructs throughout development. Implications for cognitive developmental theory and methods are discussed.

Does Early Mathematics Intervention Change the Processes Underlying Children's Learning?

Early educational intervention effects typically fade in the years following treatment, and few studies have investigated why achievement impacts diminish over time. The current study tested the effects of a preschool mathematics intervention on two aspects of children's mathematical development. We tested for separate effects of the intervention on "state" (occasion-specific) and "trait" (relatively stable) variability in mathematics achievement. Results indicated that, although the treatment had a large impact on state mathematics, the treatment had no effect on trait mathematics, or the aspect of mathematics achievement that influences stable individual differences in mathematics achievement over time. Results did suggest, however, that the intervention could affect the underlying processes in children's mathematical development by inducing more transfer of knowledge immediately following the intervention for students in the treated group.

Fadeout in an early mathematics intervention: Constraining content or preexisting differences?

A robust finding across research on early childhood educational interventions is that the treatment effect diminishes over time, with children not receiving the intervention eventually catching up to children who did. One popular explanation for fadeout of early mathematics interventions is that elementary school teachers may not teach the kind of advanced content that children are prepared for after receiving the intervention, so lower-achieving children in the control groups of early mathematics interventions catch up to the higher-achieving children in the treatment groups. An alternative explanation is that persistent individual differences in children's long-term mathematical development result more from relatively stable preexisting differences in their skills and environments than from the direct effects of previous knowledge on later knowledge. We tested these 2 hypotheses using data from an effective preschool mathematics intervention previously known to show a diminishing treatment effect over time. We compared the intervention group to a matched subset of the control group with a similar mean and variance of scores at the end of treatment. We then tested the relative contributions of factors that similarly constrain learning in children from treatment and control groups with the same level of posttreatment achievement and preexisting differences between these 2 groups to the fadeout of the treatment effect over time. We found approximately 72% of the fadeout effect to be attributable to preexisting differences between children in treatment and control groups with the same level of achievement at posttest. These differences were fully statistically attenuated by children's prior academic achievement. (PsycINFO Database Record

Social Anhedonia Is Not Just Extreme Introversion: Empirical Evidence of Distinct Constructs

Social anhedonia and introversion, two closely related constructs associated with decreased positive emotions and decreased sociability, are common in schizophrenia-spectrum personality disorders. In light of a myriad of mixed findings regarding positive emotionality in anhedonia, there has been a call to reconceptualize "anhedonia." To clarify the nature of social anhedonia, we used confirmatory factor analysis to investigate the relationship between social anhedonia and introversion. Findings were consistent with the conceptualization of social anhedonia as a separate construct from introversion-the best fitting model was one in which social anhedonia and introversion measures loaded separately. Also consistent with the conceptualization of social anhedonia as separate, we found evidence that it was associated with aspects of alexithymia above and beyond any relationship with introversion. Overall, these results have implications for the understanding of social anhedonia and for the use of it as a discriminating factor between personality disorders characterized by introversion.

Sexual selection on male vocal fundamental frequency in humans and other anthropoids

In many primates, including humans, the vocalizations of males and females differ dramatically, with male vocalizations and vocal anatomy often seeming to exaggerate apparent body size. These traits may be favoured by sexual selection because low-frequency male vocalizations intimidate rivals and/or attract females, but this hypothesis has not been systematically tested across primates, nor is it clear why competitors and potential mates should attend to vocalization frequencies. Here we show across anthropoids that sexual dimorphism in fundamental frequency (F0) increased during evolutionary transitions towards polygyny, and decreased during transitions towards monogamy. Surprisingly, humans exhibit greater F0 sexual dimorphism than any other ape. We also show that low-F0 vocalizations predict perceptions of men's dominance and attractiveness, and predict hormone profiles (low cortisol and high testosterone) related to immune function. These results suggest that low male F0 signals condition to competitors and mates, and evolved in male anthropoids in response to the intensity of mating competition.

Countries with Higher Levels of Gender Equality Show Larger National Sex Differences in Mathematics Anxiety and Relatively Lower Parental Mathematics Valuation for Girls

Despite international advancements in gender equality across a variety of societal domains, the underrepresentation of girls and women in Science, Technology, Engineering, and Mathematics (STEM) related fields persists. In this study, we explored the possibility that the sex difference in mathematics anxiety contributes to this disparity. More specifically, we tested a number of predictions from the prominent gender stratification model, which is the leading psychological theory of cross-national patterns of sex differences in mathematics anxiety and performance. To this end, we analyzed data from 761,655 15-year old students across 68 nations who participated in the Programme for International Student Assessment (PISA). Most importantly and contra predictions, we showed that economically developed and more gender equal countries have a lower overall level of mathematics anxiety, and yet a larger national sex difference in mathematics anxiety relative to less developed countries. Further, although relatively more mothers work in STEM fields in more developed countries, these parents valued, on average, mathematical competence more in their sons than their daughters. The proportion of mothers working in STEM was unrelated to sex differences in mathematics anxiety or performance. We propose that the gender stratification model fails to account for these national patterns and that an alternative model is needed. In the discussion, we suggest how an interaction between socio-cultural values and sex-specific psychological traits can better explain these patterns. We also discuss implications for policies aiming to increase girls' STEM participation.

Co-father relationships among the Suruí (Paiter) of Brazil

Partible paternity refers to the conception belief that children can have multiple fathers ("co-fathers") and is common to indigenous cultures of lowland South America. The nature of social relationships observed between co-fathers reveals information about the reproductive strategies underlying partible paternity. Here we analyze clan, genealogical, and social relationships between co-fathers for the Suruí, an indigenous horticultural population in Brazil. We show that co-fathers roughly assort into two separate categories. In the affiliative category, co-father relationships are amicable when they are between close kin, namely brothers and father-son. In the competitive category, relationships are more likely of avoidance or open hostility when between more distant kin such as cousins or unrelated men of different clans. Results therefore imply multiple types of relationships, including both cooperative and competitive contexts, under the rubric of partible paternity. These complexities of partible paternity institutions add to our knowledge of the full range of cross-cultural variation in human mating/marriage arrangements and speak to the debate on whether or not humans should be classified as cooperative breeders.

State and trait effects on individual differences in children's mathematical development

Substantial longitudinal relations between children's early mathematics achievement and their much later mathematics achievement are firmly established. These findings are seemingly at odds with studies showing that early educational interventions have diminishing effects on children's mathematics achievement across time. We hypothesized that individual differences in children's later mathematical knowledge are more an indicator of stable, underlying characteristics related to mathematics learning throughout development than of direct effects of early mathematical competency on later mathematical competency. We tested this hypothesis in two longitudinal data sets, by simultaneously modeling effects of latent traits (stable characteristics that influence learning across time) and states (e.g., prior knowledge) on children's mathematics achievement over time. Latent trait effects on children's mathematical development were substantially larger than state effects. Approximately 60% of the variance in trait mathematics achievement was accounted for by commonly used control variables, such as working memory, but residual trait effects remained larger than state effects. Implications for research and practice are discussed.

Women's preference for masculine traits is disrupted by images of male-on-female aggression

Women's preferences for men's masculinized faces and voices were assessed after women (n = 331) were primed with images of male-on-male aggression, male-on-female aggression, pathogens, and neutral scenes. Male-on-male aggression and pathogen primes were associated with increased preference for masculine traits, but the same effect emerged in the neutral condition. We show the increased preference for masculine traits was due to repeated exposure to these traits, not the priming images themselves. Images of male-on-female aggression were an exception; these elicited feelings of disgust and anger appeared to disrupt the preference for masculinized traits. The results suggest women process men's facial and vocal traits as signals of aggressive potential and lose any preference for these traits with cues indicating men might direct this aggression toward them.

Early predictors of middle school fraction knowledge

Recent findings that earlier fraction knowledge predicts later mathematics achievement raise the question of what predicts later fraction knowledge. Analyses of longitudinal data indicated that whole number magnitude knowledge in first grade predicted knowledge of fraction magnitudes in middle school, controlling for whole number arithmetic proficiency, domain general cognitive abilities, parental income and education, race, and gender. Similarly, knowledge of whole number arithmetic in first grade predicted knowledge of fraction arithmetic in middle school, controlling for whole number magnitude knowledge in first grade and the other control variables. In contrast, neither type of early whole number knowledge uniquely predicted middle school reading achievement. We discuss the implications of these findings for theories of numerical development and for improving mathematics learning.

Fitness consequences of spousal relatedness in 46 small-scale societies

Social norms that regulate reproductive and marital decisions generate impressive cross-cultural variation in the prevalence of kin marriages. In some societies, marriages among kin are the norm and this inbreeding creates intensive kinship networks concentrated within communities. In others, especially forager societies, most marriages are between more genealogically and geographically distant individuals, which generates a larger number of kin and affines of lesser relatedness in more extensive kinship networks spread out over multiple communities. Here, we investigate the fitness consequence of kin marriages across a sample of 46 small-scale societies (12,439 marriages). Results show that some non-forager societies (including horticulturalists, agriculturalists and pastoralists), but not foragers, have intensive kinship societies where fitness outcomes (measured as the number of surviving children in genealogies) peak at commonly high levels of spousal relatedness. By contrast, the extensive kinship systems of foragers have worse fitness outcomes at high levels of spousal relatedness. Overall, societies with greater levels of inbreeding showed a more positive relationship between fitness and spousal relatedness.

Human female orgasm as evolved signal: a test of two hypotheses

We present the results of a study designed to empirically test predictions derived from two hypotheses regarding human female orgasm behavior as an evolved communicative trait or signal. One hypothesis tested was the female fidelity hypothesis, which posits that human female orgasm signals a woman's sexual satisfaction and therefore her likelihood of future fidelity to a partner. The other was sire choice hypothesis, which posits that women's orgasm behavior signals increased chances of fertilization. To test the two hypotheses of human female orgasm, we administered a questionnaire to 138 females and 121 males who reported that they were currently in a romantic relationship. Key predictions of the female fidelity hypothesis were not supported. In particular, orgasm was not associated with female sexual fidelity nor was orgasm associated with male perceptions of partner sexual fidelity. However, faked orgasm was associated with female sexual infidelity and lower male relationship satisfaction. Overall, results were in greater support of the sire choice signaling hypothesis than the female fidelity hypothesis. Results also suggest that male satisfaction with, investment in, and sexual fidelity to a mate are benefits that favored the selection of orgasmic signaling in ancestral females.

Heritability and fitness correlates of personality in the Ache, a natural-fertility population in Paraguay

The current study assessed the heritability of personality in a traditional natural-fertility population, the Ache of eastern Paraguay. Self-reports (n = 110) and other-reports (n = 66) on the commonly used Big Five Personality Inventory (i.e., extraversion, agreeableness, conscientiousness, neuroticism, openness) were collected. Self-reports did not support the Five Factor Model developed with Western samples, and did not correlate with other-reports for three of the five measured personality factors. Heritability was assessed using factors that were consistent across self- and other-reports and factors assessed using other-reports that showed reliabilities similar to those found in Western samples. Analyses of these items in combination with a multi-generation pedigree (n = 2,132) revealed heritability estimates similar to those found in most Western samples, although we were not able to separately estimate the influence of the common environment on these traits. We also assessed relations between personality and reproductive success (RS), allowing for a test of several mechanisms that might be maintaining heritable variation in personality. Phenotypic analyses, based largely on other-reports, revealed that extraverted men had higher RS than other men, but no other dimensions of personality predicted RS in either sex. Mothers with more agreeable children had more children, and parents mated assortatively on personality. Of the evolutionary processes proposed to maintain variation in personality, assortative mating, selective neutrality, and temporal variation in selection pressures received the most support. However, the current study does not rule out other processes affecting the evolution and maintenance of individual differences in human personality.

Adolescents' functional numeracy is predicted by their school entry number system knowledge

One in five adults in the United States is functionally innumerate; they do not possess the mathematical competencies needed for many modern jobs. We administered functional numeracy measures used in studies of young adults’ employability and wages to 180 thirteen-year-olds. The adolescents began the study in kindergarten and participated in multiple assessments of intelligence, working memory, mathematical cognition, achievement, and in-class attentive behavior. Their number system knowledge at the beginning of first grade was defined by measures that assessed knowledge of the systematic relations among Arabic numerals and skill at using this knowledge to solve arithmetic problems. Early number system knowledge predicted functional numeracy more than six years later (ß = 0.195, p = .0014) controlling for intelligence, working memory, in-class attentive behavior, mathematical achievement, demographic and other factors, but skill at using counting procedures to solve arithmetic problems did not. In all, we identified specific beginning of schooling numerical knowledge that contributes to individual differences in adolescents’ functional numeracy and demonstrated that performance on mathematical achievement tests underestimates the importance of this early knowledge.

Women's attractiveness changes with estradiol and progesterone across the ovulatory cycle

In many species, females are more sexually attractive to males near ovulation. Some evidence suggests a similar pattern in humans, but methodological limitations prohibit firm conclusions at present, and information on physiological mechanisms underlying any such pattern is lacking. In 202 normally-cycling women, we explored whether women's attractiveness changed over the cycle as a function of two likely candidates for mediating these changes: estradiol and progesterone. We scheduled women to attend one session during the late follicular phase and another during the mid-luteal phase. At each session, facial photographs, voice recordings and saliva samples were collected. All photographs and voice recordings were subsequently rated by men for attractiveness and by women for flirtatiousness and attractiveness to men. Saliva samples were assayed for estradiol and progesterone. We found that progesterone and its interaction with estradiol negatively predicted vocal attractiveness and overall (facial plus vocal) attractiveness to men. Progesterone also negatively predicted women's facial attractiveness to men and female-rated facial attractiveness, facial flirtatiousness and vocal attractiveness, but not female-rated vocal flirtatiousness. These results strongly suggest a pattern of increased attractiveness during peak fertility in the menstrual cycle and implicate estradiol and progesterone in driving these changes.

Fractions: the new frontier for theories of numerical development

Recent research on fractions has broadened and deepened theories of numerical development. Learning about fractions requires children to recognize that many properties of whole numbers are not true of numbers in general and also to recognize that the one property that unites all real numbers is that they possess magnitudes that can be ordered on number lines. The difficulty of attaining this understanding makes the acquisition of knowledge about fractions an important issue educationally, as well as theoretically. This article examines the neural underpinnings of fraction understanding, developmental and individual differences in that understanding, and interventions that improve the understanding. Accurate representation of fraction magnitudes emerges as crucial both to conceptual understanding of fractions and to fraction arithmetic.

The codevelopment of skill at and preference for use of retrieval-based processes for solving addition problems: individual and sex differences from first to sixth grades

The ability to retrieve basic arithmetic facts from long-term memory contributes to individual and perhaps sex differences in mathematics achievement. The current study tracked the codevelopment of preference for using retrieval over other strategies to solve single-digit addition problems, independent of accuracy, and skilled use of retrieval (i.e., accuracy and reaction time [RT]) from first to sixth grades inclusive (N=311). Accurate retrieval in first grade was related to working memory capacity and intelligence, and it predicted a preference for retrieval in second grade. In later grades, the relation between skill and preference changed such that preference in one grade predicted accuracy and RT in the next grade as RT and accuracy continued to predict future gains in preference. In comparison with girls, boys had a consistent preference for retrieval over other strategies and had faster retrieval speeds, but the sex difference in retrieval accuracy varied across grades. Results indicate that ability influences early skilled retrieval, but both practice and skill influence each other in a feedback loop later in development and provide insights into the source of the sex difference in problem-solving approaches.

Competence with fractions predicts gains in mathematics achievement

Competence with fractions predicts later mathematics achievement, but the codevelopmental pattern between fractions knowledge and mathematics achievement is not well understood. We assessed this codevelopment through examination of the cross-lagged relation between a measure of conceptual knowledge of fractions and mathematics achievement in sixth and seventh grades (N=212). The cross-lagged effects indicated that performance on the sixth grade fractions concepts measure predicted 1-year gains in mathematics achievement (ß=.14, p<.01), controlling for the central executive component of working memory and intelligence, but sixth grade mathematics achievement did not predict gains on the fractions concepts measure (ß=.03, p>.50). In a follow-up assessment, we demonstrated that measures of fluency with computational fractions significantly predicted seventh grade mathematics achievement above and beyond the influence of fluency in computational whole number arithmetic, performance on number fluency and number line tasks, central executive span, and intelligence. Results provide empirical support for the hypothesis that competence with fractions underlies, in part, subsequent gains in mathematics achievement.

Fact retrieval deficits in low achieving children and children with mathematical learning disability

Using 4 years of mathematics achievement scores, groups of typically achieving children (n = 101) and low achieving children with mild (LA-mild fact retrieval; n = 97) and severe (LA-severe fact retrieval; n = 18) fact retrieval deficits and mathematically learning disabled children (MLD; n = 15) were identified. Multilevel models contrasted developing retrieval competence from second to fourth grade with developing competence in executing arithmetic procedures, in fluency of processing quantities represented by Arabic numerals and sets of objects, and in representing quantity on a number line. The retrieval deficits of LA-severe fact retrieval children were at least as debilitating as those of the children with MLD and showed less across-grade improvement. The deficits were characterized by the retrieval of counting string associates while attempting to remember addition facts, suggesting poor inhibition of irrelevant information during the retrieval process. This suggests a very specific form of working memory deficit, one that is not captured by many typically used working memory tasks. Moreover, these deficits were not related to procedural competence or performance on the other mathematical tasks, nor were they related to verbal or nonverbal intelligence, reading ability, or speed of processing, nor would they be identifiable with standard untimed mathematics achievement tests.