Parenting

Lee Kuan Yew served as founding Prime Minister of Singapore from 1959 to 1990. Under his leadership, Singapore became a first-world country in a single generation. A key driver was revolutionizing the education system:

• Teachers were highly-trained and students received personalized instruction with hands-on learning

• Students were streamed into universities, polytechnics, or technical trades

• Exceptional talent was nurtured by specialized schools for arts, sports, math, and science

In the 1960s, the high school drop-out rate was 56%. By the 1980s, it was less than 1%. Nowadays, Singapore’s students score the highest on international tests of reading, math, science, and creative problem solving.

In parallel to improving education for all students, Lee encouraged educated people to marry each other and have intelligent children. This increased Singapore’s most precious resource—the brainpower of its citizens.

Lee Kuan Yew—who is the greatest nation builder, probably that ever lived in the history of the world—he said one thing over and over and over again all his life: figure out what works and do it.

-Charlie Munger

Nature and nurture

Most parents want their kids to be happy, healthy, and wealthy.

Boost the odds for your kids with this system:

• Pick a partner with great genetics

• Be a great parent

In any given society, of the 1,000 babies born, there are so many percent near-geniuses, so many percent average, so many percent morons…It is the near-geniuses and the above-average who ultimately decide the shape of things to come…We want an equal society. We want to give everybody equal opportunities. But, in the back of our minds, we never deceive ourselves that two human beings are ever equal in their stamina, in their drive, in their dedication, in their innate ability.

-Lee Kuan Yew

Great genetics

Genetics influence happiness, health, and wealth. You and your partner’s genes will be passed on to your kids. If you’re both happy, healthy, and wealthy, there’s a good chance your kids will be too.

Genetics is the major reason why people differ in personality, mental health and illness, and learning and cognitive abilities. In essence, the most important thing that parents give to their children is their genes.

-Robert Plomin

Happy

Identical twins share the same genetics, whereas fraternal twins and siblings share half their genetics. Decades of twin and sibling research show that happiness is 35% inherited. Similarly, depression and anxiety are 30–40% inherited.

I just want my kids to love who they are, have happy lives and find something they want to do and make peace with that. Your job as a parent is to give your kids not only the instincts and talents to survive, but help them enjoy their lives.

-Susan Sarandon

Healthy

Similar to happiness, thousands of twin studies have found that genetics strongly influence most characteristics. This includes healthy behaviors, physical traits, and diseases. For example, height is 90% inherited and weight is at least 50% inherited. Short men and heavy women are at a disadvantage for dating and careers.

Attractiveness is 50–70% inherited. Of note, facial masculinity is 40–50% inherited. This means men and women with masculine faces are more likely to have unattractive sisters and daughters.

Women aged 19 to 26 are twice as fertile as 35 to 39. By 45, almost 90% of women are infertile. Also, children of older women have a higher risk of genetic diseases. For example, risk of Down syndrome and other cytogenetic abnormalities is 2 in 1,000 births for women under 30; 6 in 1,000 at 35; and 54 in 1,000 at 45.

In contrast, men’s fertility declines by only 30% in their 40s. And they can still father children in their 50s and 60s. The reason is men produce up to 100 million sperm per day, whereas women only ovulate 400–500 eggs in their lifetime.

Genetically-similar couples are more likely to have children with recessive genetics. At one extreme, babies of first cousins have a 3.5% higher rate of infant mortality. They also tend to be shorter and less intelligent in adulthood. In contrast, mixed-race individuals tend to be taller, smarter, and more attractive.

Researchers have found that women naturally prefer the smell of genetically-unrelated men, especially when they’re ovulating. However, taking oral contraception reverses this—these women prefer genetically-similar men. Contraceptive hormones cause a woman’s body to think it’s pregnant and prefer the company of family instead of strangers. Therefore, some women may wish to use non-hormonal forms of birth control such as Intrauterine Devices (IUDs).

Life is like a game of cards. The hand that is dealt you represents determinism; the way you play it is free will.

‐Jawaharlal Nehru

Wealthy

Researchers found that heritability was 23% for socioeconomic status and 54% for lifetime earnings. The top two drivers were intelligence and conscientiousness.

Intelligence is the ability to deal with complexity. It includes reasoning, problem solving, and abstract thinking. Studies with 11,000 twin pairs found that intelligence had a heritability of 40–55% in childhood and adolescence. This rose to 85% in adulthood.

Intelligence is a strong predictor of academic achievement, job performance, and wealth. Only the top 10% are competitive for the highest-level jobs. Also, intelligent people have lower risks of mental illness and other diseases.

Second to intelligence is a personality trait called conscientiousness. It has a heritability of 30–40%. Conscientious people are organized, efficient, punctual, disciplined, responsible, hard-working, and gritty. Not surprisingly, conscientiousness is a strong predictor of academic achievement, job performance, wealth, and happiness.

There are no hard problems, only problems that are hard to a certain level of intelligence. Move the smallest bit upwards, and some problems will suddenly move from “impossible” to “obvious”. Move a substantial degree upwards, and all of them will become obvious.

-Eliezer Yudkowsky

Great parenting

For the past 80 years, the Grant Study has tracked the lives of 268 male Harvard students from youth to death. The biggest finding? Love matters most. A loving childhood is a strong predictor of adult happiness and success. Men with warm mothers earn 50% more money. And men with good fathers are more likely to be happy and have happy marriages.

These results have been confirmed by thousands of studies—cherished children do best. Children need love, attention, and support from both parents. Loving parents set consistent boundaries for good behavior. They encourage personal choice and independence. When children misbehave, parents should use reasoning, brief time-outs, and positive reinforcement.

In contrast, children’s health and success are worsened by anger, harsh discipline, physical punishment, overprotection, rejection, and neglect. Researchers have found that strict fathers and tiger moms are actually harming their kids more than parents who let them run wild.

Children do better when parents love each other. But sometimes divorce is inevitable. In this case, negative effects are reduced when both parents provide love and support.

Children who fail to learn basic love and trust at home are handicapped later in mastering the assertiveness, initiative, and autonomy that are the foundation of successful adulthood.

-George Vaillant

Help at home

To help children learn to read, there is strong evidence for teaching phonics to toddlers. For math, it’s important to memorize multiplication tables and practice mental addition and subtraction. Also, hands-on learning is more effective than abstract concepts.

Finally, teach a “growth mindset”: the brain is like a muscle that grows stronger with training. Don’t praise children for being smart. Instead, praise effort and hard work.

The most important job you have is to be the teacher to your children. You are the big, great thing to them. You don’t get a rewind button. You don’t get to do it twice. Teach by what you do, not what you say. By the time they get through formal school, they would have learned more from you than from school. Provide warmth and food and everything else.

-Warren Buffett

Successful schools

The best school is one with other cherished children and firm, kind teachers. This could be homeschooling, charter schools, Montessori, or good schools in rich neighborhoods. Children’s friends are important too—peer pressure can help or hurt.

The mediocre teacher tells. The good teacher explains. The superior teacher demonstrates. The great teacher inspires.

-William Arthur Ward

Personal notes

When I was a kid, my dad constantly told me: “Hard work is the key to success”. He posted this saying around our basement walls. I’m also grateful for my mom’s unconditional love. Looking back, it gave me the subconscious security to trade my safe medical career for the roller coaster of entrepreneurship.

Finally, I used to get annoyed when my kids interrupted my work. But now I practice being fully present with them.

There is a kind of immunity about a happy childhood, not an immunity from the disasters and catastrophes that may, that almost certainly do, lie ahead, but an intrinsic immunity. Change and transience are at the heart of the human condition. But as parents we can at least give our children a happy childhood, a gift that is as certain, as unchanging, as rock solid, as any human good.

-Alison Gopnik

Love as powerful as your mother’s for you leaves its own mark…to have been loved so deeply, even though the person who loved us is gone, will give us some protection forever.

-J.K. Rowling

References

Kang T. (2004). Taking human capital investment seriously: Reflections on educational reform. Educational Research Policy Practice. 3: 63–76.

• History of educational reform in Singapore

Lee S. (2017, March 19). Singapore’s education system: Some key success factors. New Zealand Centre Political Research. https://www.nzcpr.com/singapores-education-system-some-key-success-factors/

• Singapore’s high school drop-out rate improved from 56% in the 1960s to less than 1% in the 1980s

Lee KY. (2000). From Third World to First: The Singapore story: 1965–2000. HarperCollins.

• “On the night of 14 August 1983, I dropped a bombshell in my annual National Day Rally address. Live on both our television channels, with maximum viewership, I said it was stupid for graduate men to choose less-educated and less-intelligent wives if they wanted their children to do as well as they had done. The press named it the ‘Great Marriage Debate.’ It caused a drop of 12 percentage points in votes for the PAP in the election the following year, more than I had anticipated.”

• “The capabilities of most children were between those of their two parents, with a few having lower or higher intelligence than either. Therefore, male graduates who married less-educated women were not maximizing the chances of having children who make it to university. I urged them to marry their educational equals, and encouraged educated women to have two or more children.”

• “Since that speech in 1983, I have regularly released the statistical analysis of the educational backgrounds of parents of the top 10 percent of students in national examinations. Singaporeans now accept that the better-educated and more able the parents, the more likely are the children to achieve similar levels.”

Happy

Bertels M. (2015). Genetics of wellbeing and its components satisfaction with life, happiness, and quality of life: A review and meta-analysis of heritability studies. Behav Genet. 45(2): 137–156.

• A meta-analysis of 10 studies with 55,974 twin-family individuals found that heritability of well-being was 36%

• A meta-analysis of 9 studies with 47,750 twin-family individuals found that heritability of satisfaction with life was 32%

Sullivan PF, Neale MC, Kendler KS. (2000). Genetic epidemiology of major depression: review and meta-analysis. Am J Psychiatry. 157(10): 1552–1562.

• A meta-analysis of 5 twin-family studies found that heritability of major depression was 31–42%

Hettema JM, Neale MC, Kendler KS. (2001). A review and meta-analysis of the genetic epidemiology of anxiety disorders. Am J Psychiatry. 158(10): 1568–1578.

• A meta-analysis of 5 twin-family studies found that heritability of generalized anxiety disorder was 32%

• Heritability of panic disorder was 43%

Healthy

Polderman TJC et al. (2015). Meta-analysis of the heritability of human traits based on fifty years of twin studies. Nat Genet. 47(7): 702–709.

• A meta-analysis of 17,804 traits from 2,748 studies with 14,558,903 twin pairs found that heritability averaged 49% across all traits

Silventoinen K et al. (2003). Heritability of adult body height: a comparative study of twin cohorts in eight countries. Twin Res. 6(5): 399–408.

• An analysis of 30,111 twin pairs from 8 countries found that heritability of height was 89–93%

Elks CE et al. (2012). Variability in the heritability of Body Mass Index: A systematic review and meta-regression. Front Endocrinol. 3: 29.

• A systematic review of 88 studies with 140,525 twins found that heritability of BMI was 47–90%

Jackson LA, Ervin KS. (1992). Height stereotypes of women and men: The liabilities of shortness for both sexes. Journal Social Psychology. 132(4): 433–445.

• A study of 237 college students found that short men were perceived as less socially attractive, lower professional status, less personally adjusted, less athletic, and less masculine

Stulp G et al. (2013). Are human mating preferences with respect to height reflected in actual pairings? PLoS One. 8(1): e54186.

• study of 12,502 British couples found that 92.5% of men were taller than their female partners

• Women preferred male partners who were taller by less than 25 cm (10 inches)

Tyrrell J et al. (2016). Height, body mass index, and socioeconomic status: mendelian randomisation study in UK Biobank. BMJ. 352: i582.

• A study of 119,669 British men and women found that a 1-standard deviation (SD) higher BMI (4.6 kg/m2) in women decreased annual household income by £2,940

• A 1-SD (6.3 cm) taller stature in men increased annual household income by £1,580

Mitchem DG et al. (2013). Estimating the sex-specific effects of genes on facial attractiveness and sexual dimorphism. Behav Genet. 44(3): 270–281.

• A study of 1,580 same- and opposite-sex twin pairs and siblings found that heritability of attractiveness was 50–70%

• Heritability of facial masculinity-femininity was 40–50%

Lee AJ et al. (2014). Genetic factors that increase male facial masculinity decrease facial attractiveness of female relatives. Psychol Sci. 25(2): 476–484.

• A study of 1,299 twins and siblings found that facially-masculine men tended to have facially-masculine, less-attractive sisters (effect size = 0.23)

• Facially feminine women tended to have facially feminine brothers, but this did not decrease attractiveness

• This meant men who chose feminine mates increased attractiveness of daughters with no disadvantage to sons

Dunson DB, Colombo B, Baird DD. (2002). Changes with age in the level and duration of fertility in the menstrual cycle. Hum Reprod. 17(5): 1399–1403.

• A study of 782 healthy couples found that probability of pregnancy was twice as high for women aged 19 to 26 vs. women aged 35 to 39

• Fertility for men was less affected by age, but started declining in late 30s

Harris ID et al. (2011). Fertility and the aging male. Rev Urol. 13(4): e184–e190.

• A natural history study of the Hutterite population showed that 11% of women were infertile by age 34, 33% by 40, and 87% by 45

• Other studies showed that per-cycle fertility dropped from a peak of 25–30% per month in early to mid-20s to <5% at age 40

• Men can produce up to 100 million sperm per day, whereas women ovulate 400–500 eggs over their lifetime

• A study of 8,559 pregnancies found that conception during a 12-month period was 30% less likely for men over age 40 vs. men younger than 30, even adjusting for female age

Menken J, Trussell J, Larsen U. (1986). Age and infertility. Science. 233(4771): 1389–1394.

• Compared with women aged 20 to 24, fertility was 6% lower from 25 to 29; 14% from 30 to 34; and 31% from 35 to 39

• Male fertility from 50 to 54 was 73% lower compared to early 20s

Hook EB. (1981). Rates of chromosome abnormalities at different maternal ages. Obstet Gynecol. 58(3): 282–285.

• Based on studies of live births in the 1960s and early 1970s, before the widespread use of prenatal diagnosis, it is estimated that the rate of Down syndrome and other cytogenetic abnormalities rises with maternal age: youngest ages (2 per 1,000), age 30 (2.6 per 1,000), age 35 (5.6 per 1,000), age 40 (15.8 per 1,000), and age 45 (53.7 per 1,000)

du Fossé NA et al. (2018). Advanced paternal age is associated with an increased risk of spontaneous miscarriage: a systematic review and meta-analysis. Hum Reprod Update. 26(5): 650–669.

• A meta-analysis of 9 studies found that paternal age increased risk of miscarriage: 30–34 (4%), 35–39 (15%), 40–44 (23%), and ≥40 (43%)

Johnson SL et al. (2015). Consistent age-dependent declines in human semen quality: A systematic review and meta-analysis. Ageing Research Reviews. 19: 22–33.

• A meta-analysis of 90 studies with 93,839 subjects found that semen quality had small declines with age: DNA fragmentation (effect size = -0.21), progressive motility (effect size = -0.20), sperm motility (effect size = -0.12), semen volume (effect size = -0.10), normal morphology (effect size = -0.08), total sperm count (effect size = -0.06), and sperm concentration (effect size = -0.02)

• Similarly, another study showed no decline in sperm concentration for men in their 50s

de la Rochebrochard E, Thonneau P. (2002). Paternal age and maternal age are risk factors for miscarriage; results of a multicentre European study. Hum Reprod. 17(6): 1649–1656.

• A study of 3,174 planned pregnancies found that risk of miscarriage was higher if the woman was aged ≥35 (338–387%), and much higher for couples composed of a woman ≥35 and a man ≥40 (673%)

• If the woman was 20–29, risk was higher if the man was 35–39 (31%) or 40–64 (80%)

Mixed race

Bittles AH, Black ML. (2010). Consanguinity, human evolution, and complex diseases. Proc Natl Acad Sci USA. 107(Suppl 1): 1779–1786.

• Couples related as second cousins or closer, and their offspring, represent 10.4% of global population

• Highest rates of consanguineous marriage occur in north and sub-Saharan Africa, Middle East, and west, central, and south Asia

• In these regions, even couples who regard themselves as unrelated may exhibit high levels of homozygosity because of long-established traditions of marrying within clan, tribe, caste, or biraderi boundaries

• First-cousin offspring have a death rate that is higher by 3.5%

Joshi PK et al. (2015). Directional dominance on stature and cognition in diverse human populations. Nature. 523(7561): 459–462.

• A meta-analysis of 102 cohorts with 354,224 individuals found that increased genetic homozygosity was associated with decreased height, cognitive ability, and educational attainment

• Effect sizes for offspring of first cousins were equivalent to 1.2 cm shorter; decrease in intelligence by 0.3 of a standard deviation; and 10 months’ less education

Lewis MB. (2010). Why are mixed-race people perceived as more attractive? Perception. 39(1): 136–138.

• 20 university students rated attractiveness of 1,205 black, white, and mixed-race faces

• Mixed-race faces were rated 0.5 points higher than black or white faces on a 9-point scale

• 40% of faces were mixed race, but they accounted for 65% of the top 10% and 74% of the top 5% most attractive faces

• The reason may be hybrid vigor i.e., cross-bred offspring have greater genetic fitness than pure-breds

Wedekind C et al. (1995). MHC-dependent mate preferences in humans. Proc Biol Sci. 260(1359): 245–249.

• 49 female students smelled T-shirts of 44 male students

• Women who weren’t taking oral contraceptives rated the smell of less genetically-related men as more pleasant, whereas it was the reverse for women taking contraceptives

• The contraceptive pill mimics hormones released during pregnancy, and leads to preferences for odors similar to relatives

Garver-Apgar CE et al. (2006). Major histocompatibility complex alleles, sexual responsivity, and unfaithfulness in romantic couples. Psychol Sci. 17(10): 830–835.

• A study of 48 heterosexual couples, where women were ovulating normally, found that genetic similarity decreased women’s sexual responsiveness to their partner, increased number of extra-pair sexual partners, and increased attraction to men other than their primary partner, particularly during the fertile phase of ovulatory cycles

Wealthy

Trzaskowski M et al. (2014). Genetic influence on family socioeconomic status and children’s intelligence. Intelligence. 42(100): 83–88.

• A study of 3,152 unrelated children found that heritability of family socioeconomic status was 23%

Hyytinen A et al. (2019). Heritability of lifetime earnings. Journal Economic Inequality. 17: 319–335.

• An analysis of 7,078 Finnish twins found that heritability of lifetime earnings was 41% for women and 54% for men

Intelligence

Gottfredson LS. (1997). Why g matters: The complexity of everyday life. Intelligence. 24(1): 79–132.

• Intelligence is the ability to deal with cognitive complexity or complex information processing

• It reflects the ability to reason, solve problems, think abstractly, and acquire knowledge

• Intelligence is not the amount of information people know, but their ability to recognize, acquire, organize, update, select, and apply it effectively

• One needs an IQ of about 120 (91st percentile) to be competitive for the highest-level jobs

Haworth CMA et al. (2010). The heritability of general cognitive ability increases linearly from childhood to young adulthood. Mol Psychiatry. 15(11): 1112–1120.

• An analysis of 11,000 twin pairs from 4 countries found that heritability of intelligence increased linearly with age: 41% in childhood (9 years), 55% in adolescence (12 years), and 66% in young adulthood (17 years)

Panizzon MS et al. (2014). Genetic and environmental influences on general cognitive ability: Is g a valid latent construct? Intelligence. 43: 65–76.

• A twin study of 1,237 individuals found that heritability of intelligence by middle age was 86%

Roth B et al. (2015). Intelligence and school grades: A meta-analysis. Intelligence. 53: 118–137.

• A meta-analysis of 240 independent samples with 105,185 participants found that school grades had a correlation of 54% with intelligence

Schmidt FL, Hunter JE. (1998). The validity and utility of selection methods in personnel psychology: Practical and theoretical implications of 85 years of research findings. Psychol Bull. 124(2): 262–274.

• A meta-analysis of 85 years of personnel selection research found that predictive validity for overall job performance was 56% for General Mental Ability (GMA) tests, 38% for integrity tests, and 30% for conscientiousness tests

• There was an 11% gain from supplementing GMA tests with integrity tests, and a 9% gain from supplementing with conscientiousness tests

Strenze T. (2007). Intelligence and socioeconomic success: A meta-analytic review of longitudinal research. Intelligence. 35(5): 401–426.

• A meta-analysis of 85 data sets found that intelligence was associated with education (56%), occupation (43%), and income (20%)

Schmidt FL, Hunter J. (2004). General mental ability in the world of work: occupational attainment and job performance. J Pers Soc Psychol. 86(1): 162–173.

• A review of studies found that childhood intelligence scores predicted 53% of income and 51% of adult occupational level

• A meta-analysis of 425 studies with 32,124 workers found that intelligence predicted 58% of performance for high-complexity jobs (professional, scientific, and upper management)

• As job experience increased, predictive validity of intelligence also increased (36% for 0–6 years experience and 59% for more than 12 years)

• Across 373 studies, predictive validity of job experience was only 18%

• Intelligence was 60–80% more influential than conscientiousness at predicting career success

• For predicting job performance, integrity tests increased validity by 27% vs. intelligence alone

Calvin CM et al. (2010). Intelligence in youth and all-cause-mortality: systematic review with meta-analysis. Int J Epidemiol. 40(3): 626–644.

• A meta-analysis of 16 studies with 1,107,222 individuals found that a 1-standard deviation advantage in cognitive test scores lowered risk of death by 24% during a 17- to 69-year follow-up

Deary IJ et al. (2015). Intelligence and personality as predictors of illness and death: How researchers in differential psychology and chronic disease epidemiology are collaborating to understand and address health inequalities. Psychol Sci Public Interest. 11(2): 53–79.

• A review of studies found that a 1 standard deviation (SD) disadvantage in intelligence increased risks of alcohol-related disorders (75%), schizophrenia (60%), mood disorders (50%), and coronary heart disease (16%)

• A 1-SD advantage in intelligence reduced risks of death by homicide (51%) and stroke (32%)

Conscientiousness

Vukasović T, Bratko D. (2015). Heritability of personality: A meta-analysis of behavior genetic studies. Psychol Bull. 141(4): 769–785. 

• A meta-analysis of 39 studies with 113,452 participants found that heritability of personality was 40%

• Heritability of conscientiousness was 31%

Jang KL, Livesley WJ, Vernon PA. (1996). Heritability of the big five personality dimensions and their facets: a twin study. J Pers. 64(3): 577–591.

• A study of 250 twin pairs found that heritability of conscientiousness was 44%

Wilmot MP, Ones DS. (2019). A century of research on conscientiousness at work. Proc Natl Acad Sci USA. 116(46): 23004–23010.

• An analysis of 92 meta-analyses of >2,500 studies with >1.1 million participants found that conscientiousness had positive effects for 98% of variables with an overall effect size of 0.20

• Conscientiousness was the most potent noncognitive predictor of occupational performance

• Characteristic themes included: motivation for goal-directed performance; preference for more predictable environments; interpersonal responsibility for shared goals; commitment; perseverance; self-regulatory restraint to avoid counterproductivity; and proficient performance for goals

• Positive effects of conscientiousness were reduced for high-complexity vs. low-to-moderate complexity occupations

Credé M, Tynan MC, Harms, PD. (2017). Much ado about grit: A meta-analytic synthesis of the grit literature. J Pers Soc Psychol. 113(3): 492–511.

• A meta-analysis of 73 studies with 66,807 participants found that grit was correlated with conscientiousness (effect size = 0.84), self-control (effect size = 0.72), mental toughness (effect size = 0.46), positive affect (effect size = 0.46), and self-efficacy (effect size = 0.43)

• Conscientiousness was correlated with perseverance (effect size = 0.83) and consistency (effect size = 0.61)

• Perseverance was a better predictor of performance than consistency or grit

• Grit added little incremental value for prediction of performance above conscientiousness, which suggested it was redundant with conscientiousness

Poropat AE. (2009). A meta-analysis of the five-factor model of personality and academic performance. Psychol Bull. 135(2): 322–338.

• A meta-analysis of 80 studies with >70,000 individuals found that conscientiousness increased academic performance (effect size = 0.46)

Duckworth AL et al. (2012). Who does well in life? Conscientious adults excel in both objective and subjective success. Front Psychol. 3: 356.

• A study of 9,646 American adults found that conscientiousness increased life satisfaction (effect size = 0.20), positive affect (effect size = 0.17), wealth (effect size = 0.16), and lifetime income (effect size = 0.13)

Great parenting

Vaillant GE. (2012). Triumphs of experience: The men of the Harvard Grant Study. Harvard University Press.

Ali S et al. (2019). They love me not: A meta-analysis of relations between parental undifferentiated rejection and offspring’s psychological maladjustment. Journal Cross-Cultural Psychology. 50(2): 185–199.

• A meta-analysis of 102 studies from 17 countries with 24,003 individuals found that maternal and paternal rejection was associated with psychological maladjustment in childhood and adulthood (effect sizes = 0.48 and 0.35, respectively)

• Maternal rejection had a stronger negative effect than paternal rejection

• Rejection is withdrawal of parental love, warmth, and affection

• Rejected children tended to develop anxiety, insecurity, anger, hostility, aggression, passive aggression, dependence, impaired self-esteem, impaired self-adequacy, emotional instability, emotional unresponsiveness, negative worldview, and cognitive distortions

Leijten P et al. (2019). Meta-analyses: Key parenting program components for disruptive child behavior. J Am Acad Child Adolesc Psychiatry. 58(2): 180–190.

• A meta-analysis of 154 studies found that disruptive children’s behavior was improved by positive reinforcement (effect size = 0.28) and natural/logical consequences as a disciplining technique (effect size = 0.21)

Koehn AJ, Kerns KA. (2018). Parent-child attachment: meta-analysis of associations with parenting behaviors in middle childhood and adolescence. Attach Hum Dev. 20(4): 378–405.

• A meta-analysis of 40 studies found that secure attachment between parent and child was associated with parental responsiveness (effect size = 0.31), supporting child autonomy (effect size = 0.18), and behavioral control (effect size = 0.17)

• Behavioral control is defined as not harsh parenting, and includes reasoning, setting and enforcing standards for behavior, monitoring, and consistent discipline

Leijten P et al. (2018). Parenting behaviors that shape child compliance: A multilevel meta-analysis. PLoS One. 13(10): e0204929.

• A meta-analysis of 19 studies found that child compliance was improved by “time-outs” and briefly ignoring the child after non-compliance

Khaleque A. (2017). Perceived parental hostility and aggression, and children’s psychological maladjustment, and negative personality dispositions: A meta-analysis. Journal Child Family Studies. 26(4): 977–988.

• A meta-analysis of 35 studies found that maternal and paternal hostility/aggression was associated with children’s psychological maladjustment (effect sizes = 0.46 and 0.40, respectively)

• Hostility and aggression are feelings of enmity, anger, or resentment that lead to hurtful verbal and physical behavior

Pinquart M. (2017). Associations of parenting dimensions and styles with externalizing problems of children and adolescents: An updated meta-analysis. Dev Psychol. 53(5): 873–932.

• A review of meta-analyses found that behavioral problems were associated with psychological control (effect size = 0.23), harsh control (effect size = 0.21), overprotection (effect size = 0.21), corporal punishment (effect size = 0.21), neglectful parenting (effect size = 0.19), authoritarian parenting (effect size = 0.16), and permissive parenting (effect size = 0.08)

• Behavioral problems were decreased by clarity of rules (effect size = 0.23), authoritative parenting (effect size = 0.19), parental support (effect size = 0.19), behavioral control (effect size = 0.19), parental warmth (effect size = 0.18), and autonomy granting (effect size = 0.11)

• Authoritative parenting refers to high warmth and high behavioral control, whereas authoritarian parenting refers to low warmth and harsh control

Khaleque A, Ali S. (2017). A systematic review of meta‐analyses of research on interpersonal acceptance–rejection theory: Constructs and measures. Journal Family Theory Review. 9(4): 441–458.

• A review of 12 meta-analyses with 149,440 individuals found that parental acceptance improved psychological adjustment in childhood and adulthood (effect sizes = 0.51 and 0.46, respectively)

• Perceived parental acceptance accounted for 26% of variability in childhood psychological adjustment vs. 21% for adulthood

• Parental acceptance refers to love, warmth, affection, and care

Valcan DS, Davis H, Pino-Pasternak D. (2017). Parental behaviours predicting early childhood executive functions: a meta-analysis. Educational Psychology Review. 30: 607–649.

• A meta-analysis of 42 studies found that childhood executive functions were improved by parental behaviors that were warm/responsive/sensitive (effective size = 0.25) and autonomy support/scaffolding/cognitive stimulation (effect size = 0.20)

• Executive functions were decreased by control/intrusiveness/detachment (effect size = 0.22)

Vasquez AC et al. (2015). Parent autonomy support, academic achievement, and psychosocial functioning: a meta-analysis of research. Educational Psychology Review. 28: 605–644.

• A meta-analysis of 36 studies found that parental support for children’s autonomy increased psychological health (effect size = 0.38), perceived competence (effect size = 0.21), autonomous motivation (effect size = 0.19), perceived control (effect size = 0.15), effort (effect size = 0.12), and academic achievement (effect size = 0.11)

Lee LO et al. (2015). Do cherished children age successfully? Longitudinal findings from the Veterans Affairs Normative Aging Study. Psychol Aging. 30(4): 894–910.

• A study of 1,076 men found that those who reported being cherished as children had stronger social supports in midlife, greater happiness, greater psychological well-being, and higher autonomy than those who were harshly disciplined, or experienced ordinary care

• Cherished was defined as strong support and some losses; harshly disciplined included low positive reinforcement and nonnormative stressors; and ordinary care was few stressors and low parental attention

Kim SY et al. (2013). Does “Tiger Parenting” exist? Parenting profiles of Chinese Americans and adolescent developmental outcomes. Asian Am J Psychol. 4(1): 7–18.  

• An 8-year study of 444 Chinese American families found that supportive parenting was associated with the best developmental outcomes, followed by easygoing parenting, tiger parenting, and harsh parenting

• Tiger parenting was associated with lower GPAs, more depressive symptoms, and a greater sense of alienation

Rothrauff TC, Cooney TM, An JS. (2009). Remembered parenting styles and adjustment in middle and late adulthood. J Gerontol B Psychol Sci Soc Sci. 64B(1): 137–146.

• A study of 2,232 adults found that those with authoritative parents had better psychological well-being and fewer depressive symptoms than those with authoritarian or uninvolved parents

• Those with uninvolved parents reported greater substance abuse

Patall EA, Cooper H, Robinson JC. (2008). The effects of choice on intrinsic motivation and related outcomes: a meta-analysis of research findings. Psychol Bull. 134(2): 270–300.

• A meta-analysis of 41 studies found that choice improved task performance (effect size = 0.32), intrinsic motivation (effect size = 0.30), and effort (effect size = 0.22)

Jeynes WH. (2007). The relationship between parental involvement and urban secondary school student academic achievement: A meta-analysis. Urban Education. 42(1): 82–110.

• A meta-analysis of 52 studies found that parental involvement improved educational outcomes (effect size = 0.50–0.55)

Divorce and children

Auersperg F et al. (2019). Long-term effects of parental divorce on mental health - A meta-analysis. J Psychiatr Res. 119: 107–115.

• A meta-analysis of 54 studies with 506,299 participants found that divorce increased children’s risks of smoking (64%), suicidal thoughts (48%), distress (48%), doing drugs (45%), alcohol abuse (43%), suicide attempt (35%), depression (29%), and anxiety (12%)

Adamsons K, Johnson SK. (2013). An updated and expanded meta-analysis of nonresident fathering and child well-being. J Fam Psychol. 27(4): 589–599.

• A meta-analysis of 52 studies with children of divorce found that father involvement was associated with child social well-being (effect size = 0.15)

King V, Sobolewski JM. (2006). Nonresident fathers’ contributions to adolescent well-being. J Marriage Fam. 68(3): 537–557.

• A study of 453 adolescents with divorced parents found that close relationships with both parents improved school grades (effect size = 0.17) and decreased behavioral problems (effect size = 0.20)

• Having strong ties to one parent was nearly as beneficial as having strong ties to both parents, with only a limited advantage if the stronger tie was to the mother

Help at home

Ehri LC et al. (2001). Systematic phonics instruction helps students learn to read: Evidence from the National Reading Panel’s meta-analysis. Journal Direct Instruction. 2(2): 121–166.

• A meta-analysis of phonics instruction found it improved learning to read (effect size = 0.41), especially when started before Grade 1 (effect size = 0.55)

Cason M, Young J, Kuehnert E. (2019). A meta-analysis of the effects of numerical competency development on achievement: Recommendations for mathematics educators. Investigations Mathematics Learning. 11(2): 134–147.

• A meta-analysis of 17 studies found that development of numerical competency increased math achievement (effect size = 0.88)

• Math fact fluency is the ability to recall basic addition, subtraction, multiplication, and division facts accurately and quickly, and mastery relies on rote memorization and repeated practice

Carbonneau KJ, Marley SC, Selig JP. (2013). A meta-analysis of the efficacy of teaching mathematics with concrete manipulatives. Journal Educational Psychology. 105(2): 380–400.

• A meta-analysis of 55 studies with 7,237 students found that teaching math with concrete manipulatives was more effective (effect size = 0.37)

Doo MY, Bonk CJ, Heo H. (2020). A meta-analysis of scaffolding effects in online learning in higher education. International Review Research Open Distributed Learning. 21(3): 60–80.

• A meta-analysis of 18 studies found that scaffolding in online learning improved learning outcomes (effect size = 0.87)

Yeager DS et al. (2019). A national experiment reveals where a growth mindset improves achievement. Nature. 573(7774): 364–369.

• 6,000 students were given 1 hour of online training for a growth mindset (“the brain is like a muscle that grows stronger with practice”)

• Among lower-achieving students, training improved grades by 0.10 grade points

• A growth mindset was more effective when peers supported the training (effect size = 0.23)

Royer DJ et al. (2019). A systematic review of teacher-delivered behavior-specific praise on K–12 student performance. Remedial Special Education. 40(2): 112–128.

• A systematic review of 6 studies of behavior-specific praise found it increased student academic outcomes and/or reduced inappropriate behavior (effect size = 0.88)

Successful schools

Smith-Woolley E at al. (2018). Differences in exam performance between pupils attending selective and non-selective schools mirror the genetic differences between them. NPJ Sci Learn. 3: 3.

• A study of 4,814 U.K. students found that exam performance differences between non-selective public schools, selective public schools, and selective private schools were primarily due to genetic characteristics involved in student admission

Ray BD. (2017). A systematic review of the empirical research on selected aspects of homeschooling as a school choice. Journal School Choice. 11(4): 604–621.

• A review of studies found that most showed a positive effect for homeschooling on academic achievement

Cheng A et al. (2017). “No excuses” charter schools: A meta-analysis of the experimental evidence on student achievement. Journal School Choice. 11(2): 209–238.

• A meta-analysis of 14 studies found that “no excuses” charter schools improved English achievement by 9% of a standard deviation (SD), and math by 19% of an SD

• “No excuses” refers to schools with management freedom, performance goals based on measurable metrics, rigorous testing, strict discipline, and a pervasive focus on academic achievement

Marshall C. (2017). Montessori education: a review of the evidence base. NPJ Sci Learn. 2: 11.

• There is strong evidence that certain Montessori methods are effective, such as early literacy through phonics and a sensorial foundation for math

Perry L, McConney A. (2010). Does the SES of the school matter? Teachers College Record. 112(4): 1137–1162.

• An Australian study of 320 secondary schools with 12,000 students found that being part of a high socioeconomic status (SES) vs. low-SES school was associated with an improvement of 0.6 standard deviations for reading, math, and science for all students regardless of their SES

Sirin SR. (2005). Socioeconomic status and academic achievement: A meta-analytic review of research. Review Educational Research. 75(3): 417–453.

• A meta-analysis of 74 studies with 101,157 students found that socioeconomic status increased academic achievement (effect size = 0.30)

Liu J et al. (2017). The influence of peer behavior as a function of social and cultural closeness: A meta-analysis of normative influence on adolescent smoking initiation and continuation. Psychol Bull. 143(10): 1082–1115.

• A meta-analysis of 75 studies found that having peers who smoked increased odds of teenagers starting and continuing to smoke by 200%

Sacerdote B. (2001). Peer effects with random assignment: Results for Dartmouth roommates. Quarterly Journal Economics. 116(2): 681–704.

• A study of 1,589 college students found that a 1-standard deviation increase in roommate GPA was associated with a 0.05 increase in own GPA

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