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.

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.

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.

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.

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.

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.

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.

CAUSAL INFERENCE AND THE SPATIAL-MATH LINK IN EARLY CHILDHOOD.

Verdine et al. (2017) present compelling evidence for a causal effect of spatial skills on children's mathematics achievement in early childhood. In additional analyses of the correlation matrix reported by Verdine et al., I present evidence that the spatial-math link is not merely an epiphenomenon of general cognitive demands of both tasks. However, the question of whether the link is due to a causal effect of spatial skills on mathematics skills, a causal effect of mathematics skills on spatial skills, or common factors influencing both during this developmental period is a more difficult one to answer. I present a well-fitting model that implies factors influencing both are largely responsible for the correlations among mathematics and spatial skills across this developmental period. This analysis is far from a complete account of the spatial-math link in early childhood; however, I end with recommendations for moving forward most efficiently.

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.

Comparative study of reproductive skew and pair-bond stability using genealogies from 80 small-scale human societies.

OBJECTIVES: Genealogies contain information on the prevalence of different sibling types that result from past reproductive behavior. Full sibling sets stem from stable monogamy, paternal half siblings primarily indicate male reproductive skew, and maternal half siblings reflect unstable pair bonds. METHODS: Full and half sibling types are calculated for a total of 61,181 siblings from published genealogies for 80 small-scale societies, including foragers, horticulturalists, agriculturalists, and pastoralists from around the world. RESULTS: Most siblings are full (61%) followed by paternal half siblings (27%) and maternal half siblings (13%). Paternal half siblings are positively correlated with more polygynous marriages, higher at low latitudes, and slightly higher in nonforagers, Maternal half sibling fractions are slightly higher at low latitudes but do not vary with subsistence. Partible paternity societies in Amazonia have more paternal half siblings indicating higher male reproductive skew. CONCLUSIONS: Sibling counts from genealogies provide a convenient method to simultaneously investigate the reproductive skew and pair-bond stability dimensions of human mating systems cross-culturally. Am. J. Hum. Biol. 28:335-342, 2016. © 2015 Wiley Periodicals, Inc.

Development of fraction concepts and procedures in U.S. and Chinese children.

We compared knowledge of fraction concepts and procedures among sixth and eighth graders in China and the United States. As anticipated, Chinese middle school children had higher knowledge of fraction concepts and procedures than U.S. children in the same grades, and the difference in procedural knowledge was much larger than the difference in conceptual knowledge. Of particular interest, national differences in knowledge of fraction concepts were fully mediated by differences in knowledge of fraction procedures, and differences between the knowledge of Chinese and U.S. children were most pronounced among the lowest achieving children within each country. Based on these and previous results, a theoretical model of the mutually facilitative interaction between conceptual and procedural knowledge of fractions is proposed and discussed.

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.

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.

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.

Marrying kin in small-scale societies.

OBJECTIVES: Marriages among kin have the dual effect of both increasing average group relatedness as well as reducing the total number of kin by eliminating more genealogically and geographically distant individuals from kinship networks. Marriage decisions therefore face a tradeoff between density of kin, or formation of intensive kinship systems, and the diversity of kin, or extensive kinship systems. This article tests the hypothesis that extensive kinship systems best characterize hunter-gatherer societies, whereas more intensive forms of subsistence, like horticultural, agricultural, and pastoral economies, are more likely to have intensive kinship systems. METHODS: Here, we investigate the wide range of variation in prevalence of kin marriages across a sample of 46 small-scale societies, split evenly between hunter-gatherers and agropastoralists (including horticulturalists), using genealogies that range in depth from 4 to 16 generations. Regression methods examine how subsistence and polygyny relate to spousal relatedness and inbreeding across societies. RESULTS: On average, hunter-gatherers show limited numbers of kin marriages and low levels of inbreeding, whereas some agropastoralists are characterized by much higher levels of both, especially in societies where polygynous marriages are more common. CONCLUSION: Intensive kinship systems emerge in some intensive economies. This pattern may have favored a kin-selected increase in more large-scale cooperation and inequality occurring relatively recently in human history after the advent of domesticated plants and animals.

Relations of different types of numerical magnitude representations to each other and to mathematics achievement.

We examined relations between symbolic and non-symbolic numerical magnitude representations, between whole number and fraction representations, and between these representations and overall mathematics achievement in fifth graders. Fraction and whole number symbolic and non-symbolic numerical magnitude understandings were measured using both magnitude comparison and number line estimation tasks. After controlling for non-mathematical cognitive proficiency, both symbolic and non-symbolic numerical magnitude understandings were uniquely related to mathematics achievement, but the relation was much stronger for symbolic numbers. A meta-analysis of 19 published studies indicated that relations between non-symbolic numerical magnitude knowledge and mathematics achievement are present but tend to be weak, especially beyond 6 years of age.

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.

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.