Grit: The Power of Passion and Perseverance

Assessing Individual Differences in
Human Behavior: New Concepts, Methods, and Findings
, ed. David John Lubinski and René V. Dawis (Palo Alto, CA: Davies-
Black Publishing, 1995): 233–59.
having a sweet tooth
:
Fiona M. Breen, Robert Plomin, and Jane Wardle, “Heritability of Food Preferences in Young Children,”
Physiology & Behavior
88 (2006): 443–47.
end up a chain-smoker
:
Gary E. Swan et al., “Smoking and Alcohol Consumption in Adult Male Twins: Genetic Heritability and
Shared Environmental Influences,” 
Journal of Substance Abuse
2 (1990): 39–50.
getting skin cancer
:
Paul Lichtenstein et al. “Environmental and Heritable Factors in the Causation of Cancer—Analyses of Cohorts
of Twins from Sweden, Denmark, and Finland,” 
New England Journal of Medicine
343 (2000): 78–85.
carry a tune
:
Elizabeth Theusch and Jane Gitschier, “Absolute Pitch Twin Study and Segregation Analysis,” 
Twin Research and
Human Genetics
14 (2011): 173–78.
dunk a basketball
:
Lisa M. Guth and Stephen M. Roth, “Genetic Influence and Athletic Performance,” 
Current Opinion in
Pediatrics
25 (2013): 653–58.
solve a quadratic equation:
Bonamy Oliver et al., “A Twin Study of Teacher-Reported Mathematics Performance and Low
Performance in 7-Year-Olds,” 
Journal of Educational Psychology
96 (2004): 504–17.
“I could only swim breaststroke”
:
Chambliss, interview.
“I had horribly bad coaches”
:
Chambliss, interview. The tremendous importance of teacher quality to trajectories of academic
achievement is documented in Eric A. Hanushek, “Valuing Teachers: How Much Is a Good Teacher Worth?” 
Education Next
11
(2011), 40–45.
researchers in London
:
Personal communication with Robert Plomin, June 21, 2015. For a review of heritability of personality traits,
see Turkheimer, Pettersson, and Horn, “Phenotypic Null Hypothesis.” It’s worth noting that there are behavioral genetics studies that
do not rely on twins, and also that heritability is a topic too complex to fully summarize here. In particular, there are interactions
between different genes, between genes and the environment, and epigenetic effects. Relatedly, there is an ongoing debate as to the
proportion of environmental influence that can be attributed to parenting. Definitively teasing apart the effects of parenting from
genetic heritage is difficult. Chiefly, this is because you can’t randomly swap human children to live with different parents. However,
you can do exactly that with rat pups and their moms. You can, for example, randomly assign rat pups to grow up with very nurturing
mothers or very negligent ones. Neurobiologist Michael Meaney has done exactly that, and he has found that nurturing rats—who lick
and groom and nurse their pups more than average—raise pups who are less stressed when dealing with challenging situations. The
effects last into adulthood, and in fact, rat pups who are born to low-lick moms but, within twenty-four hours of birth, are switched to
be raised by high-lick moms, grow up to be high-lick moms themselves. See Darlene Francis, Josie Diorio, Dong Liu, and Michael J.
Meaney, “Nongenomic Transmission Across Generations of Maternal Behavior and Stress Responses in the Rat,” 
Science
286
(1999): 1155–58.

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traits are polygenic
:
Christopher F. Chabris et al., “The Fourth Law of Behavioral Genetics,” 
Current Directions in Psychological
Science
24 (2015): 304–12.
at least 697 different genes
:
Andrew R. Wood et al., “Defining the Role of Common Variation in the Genomic and Biological
Architecture of Adult Human Height,”