Grit

Chapter 5: Grit is Changeable

All behavioral traits have contributions both from genetics and from the environment. When a trait changes rapidly in a population over time, this suggests the environment is the major cause, since genetics hasn’t had the time to change much.

  • The average male height increased from 5 feet 5 inches in 1850 to 5 feet 10 inches today. Since our genetics haven’t changed much since then, environmental influences like nutrition are responsible.
  • The Flynn effect finds that the average IQ today, calibrated to 1900 standards, would be somewhere around 130. Our brains aren’t necessarily biologically smarter - better, faster education may be responsible.

Duckworth tries to apply this logic to show that grit has some portion due to environment and is thus malleable. (Shortform note: Because if grit were purely genetic, the book would be self-defeating – you either have grit or you don’t! Time to go home.)

In unpublished twin studies, the heritability of perseverance is estimated to be 37%, and passion 20%. Supposedly, the rest of the contribution is from the environment.

Also, in a survey of US adults, grit rises steadily over age:

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Here are possible explanations for this:

  • Maturation could be genetically programmed – evolutionarily, grit may not be as beneficial in early years when seeking mates, and it may be more helpful later when caring for a family.
  • Older people could have endured more hardship throughout their lives (e.g. by surviving through World War 2 and the Cold War) and thus trained grit.
  • Maturation happens naturally over time as people learn that grit is a successful strategy for accomplishing goals, and that the opposite – quitting plans, shifting goals, starting over – leads to failure and is unsatisfying. Furthermore, life experiences – like getting a job, having children, caring for parents – require us to mature and adopt more grit.

Because we don’t have longitudinal studies of grit, we can’t distinguish between these explanations, but the third is Duckworth’s favorite. Anecdotally, people change when new expectations are thrust upon them – imagine the teen who sleeps in daily, but then enlists in the military and is punished for waking up past 6 AM. Grit can be grown.