Reproduction Number
The Contribution of Cognitive and Noncognitive Skills to Intergenerational Social Mobility
Matt McGue et al.
Psychological Science, forthcoming
Abstract:
We investigated intergenerational educational and occupational mobility in a sample of 2,594 adult offspring and 2,530 of their parents. Participants completed assessments of general cognitive ability and five noncognitive factors related to social achievement; 88% were also genotyped, allowing computation of educational-attainment polygenic scores. Most offspring were socially mobile. Offspring who scored at least 1 standard deviation higher than their parents on both cognitive and noncognitive measures rarely moved down and frequently moved up. Polygenic scores were also associated with social mobility. Inheritance of a favorable subset of parent alleles was associated with moving up, and inheritance of an unfavorable subset was associated with moving down. Parents’ education did not moderate the association of offspring’s skill with mobility, suggesting that low-skilled offspring from advantaged homes were not protected from downward mobility. These data suggest that cognitive and noncognitive skills as well as genetic factors contribute to the reordering of social standing that takes place across generations.
Should Children Do More Enrichment Activities? Leveraging Bunching to Correct for Endogeneity
Carolina Caetano, Gregorio Caetano & Eric Reed Nielsen
Federal Reserve Working Paper, May 2020
Abstract:
We study the effects of enrichment activities such as reading, homework, and extracurricular lessons on children's cognitive and non-cognitive skills. We take into consideration that children forgo alternative activities, such as play and socializing, in order to spend time on enrichment. Our study controls for selection on unobservables using a novel approach which leverages the fact that many children spend zero hours per week on enrichment activities. At zero enrichment, confounders vary but enrichment does not, which gives us direct information about the effect of confounders on skills. Using time diary data available in the Panel Study of Income Dynamics (PSID), we find that the net effect of enrichment is zero for cognitive skills and negative for non-cognitive skills, which suggests that enrichment may be crowding out more productive activities on the margin. The negative effects on non-cognitive skills are concentrated in higher-income students in high school, consistent with elevated academic competition related to college admissions.
Tuning into the real effect of smartphone use on parenting: A multiverse analysis
Kathryn Modecki et al.
Journal of Child Psychology and Psychiatry, forthcoming
Methods: Based on a sample of n = 3,659 parents collected in partnership with a national public broadcaster, we conducted a multiverse analysis. We explored 84 different analytic choices to address whether associations were weak versus robust, and provide clearer direction for measurement, theory, and practice. Effects were assessed in relation to p values, effect sizes, and AIC; we further conducted a meta‐analytic sensitivity check.
Results: Direct associations between smartphone use and parenting were relatively weak and mixed. Instead, the relation between use and parenting depended on level of technological interference. This pattern was particularly robust for family displacement. At low levels of displacing time with family using technology, more smartphone use was associated with better (not worse) parenting.
The Babies of Mortgage Market Deregulation
Isaac Hacamo
Review of Financial Studies, forthcoming
Abstract:
This paper documents that mortgage market deregulation helps mitigate the risk of population aging by affecting a foundational family-level decision: the choice to have children. Using a U.S. federal regulator ruling, I show that young households fully exposed to mortgage market deregulation increase their probability of purchasing a home and having a child by 6 percentage points. Supplemental tests reject alternative hypotheses based on income or housing wealth growth and, instead, suggest that access to space is the relevant economic mechanism. Collectively, the evidence indicates that increased access to mortgage credit affects the total number of children in the economy.
Chemical signals from eggs facilitate cryptic female choice in humans
John Fitzpatrick et al.
Proceedings of the Royal Society: Biological Sciences, June 2020
Abstract:
Mate choice can continue after mating via chemical communication between the female reproductive system and sperm. While there is a growing appreciation that females can bias sperm use and paternity by exerting cryptic female choice for preferred males, we know surprisingly little about the mechanisms underlying these post-mating choices. In particular, whether chemical signals released from eggs (chemoattractants) allow females to exert cryptic female choice to favour sperm from specific males remains an open question, particularly in species (including humans) where adults exercise pre-mating mate choice. Here, we adapt a classic dichotomous mate choice assay to the microscopic scale to assess gamete-mediated mate choice in humans. We examined how sperm respond to follicular fluid, a source of human sperm chemoattractants, from either their partner or a non-partner female when experiencing a simultaneous or non-simultaneous choice between follicular fluids. We report robust evidence under these two distinct experimental conditions that follicular fluid from different females consistently and differentially attracts sperm from specific males. This chemoattractant-moderated choice of sperm offers eggs an avenue to exercise independent mate preference. Indeed, gamete-mediated mate choice did not reinforce pre-mating human mate choice decisions. Our results demonstrate that chemoattractants facilitate gamete-mediated mate choice in humans, which offers females the opportunity to exert cryptic female choice for sperm from specific males.
An age-dependent ovulatory strategy explains the evolution of dizygotic twinning in humans
Wade Hazel et al.
Nature Ecology & Evolution, July 2020, Pages 987-992
Abstract:
Dizygotic twinning, the simultaneous birth of siblings when multiple ova are released, is an evolutionary paradox. Twin-bearing mothers often have elevated fitness, but despite twinning being heritable, twin births occur only at low frequencies in human populations. We resolve this paradox by showing that twinning and non-twinning are not competing strategies; instead, dizygotic twinning is the outcome of an adaptive conditional ovulatory strategy of switching from single to double ovulation with increasing age. This conditional strategy, when coupled with the well-known decline in fertility as women age, maximizes reproductive success and explains the increase and subsequent decrease in the twinning rate with maternal age that is observed across human populations. We show that the most successful ovulatory strategy would be to always double ovulate as an insurance against early fetal loss, but to never bear twins. This finding supports the hypothesis that twinning is a by-product of selection for double ovulation rather than selection for twinning.