Critical windows: why early development locks in so many traits
From accents learned in childhood to hormone-driven sexual development and traits set by early life experience, several experts show that timing in development shapes outcomes that are hard to change later. It explains why early exposures, good and bad, carry outsized weight.
What is a critical window in development? Show answer
A short period early in life when an experience or signal sets a trait in a lasting way that the same signal would not later.
Why are children who stay indoors more likely to become nearsighted? Show answer
Light early in life triggers growth factors that control how much the eyeball elongates, according to David Linden.
What explained the difference in heat stroke among Japanese soldiers? Show answer
Soldiers raised in the warm south had more sweat glands connected to nerves; the pattern was set by childhood climate, not genes.
How heritable is speech accent, and where does it come from? Show answer
It is not heritable at all; it comes from the speech heard in childhood, mostly from peers and not from family.
What happened to children who were in the womb during the 1918 flu pandemic? Show answer
Rates of schizophrenia rose about fourfold, from about 1 percent to 4 percent, and boys were slightly shorter on average.
Why does Erich Jarvis think the window for speech closes? Show answer
The brain can hold only so much, and for survival it solidifies what was learned in childhood instead of constantly overwriting it.
Why do humans stay more plastic than other animals, according to Jarvis? Show answer
Humans have an extra copy of a gene called SRGAP2 that keeps speech circuits and other brain regions in a more immature state through life.
Why do people raised with several languages find new ones easier? Show answer
Not because their brains are more plastic, but because they kept a wider set of phonemes they can recombine.
Which hormone builds the male genitals in the fetus? Show answer
Dihydrotestosterone, made from testosterone by the enzyme 5-alpha reductase, not testosterone itself.
What masculinizes the brain, according to Huberman? Show answer
Estrogen, converted from testosterone inside neurons, sets up the circuitry; testosterone later controls the display of those behaviors.
What exposures does Huberman warn about during puberty? Show answer
Cannabis and alcohol, which he says can raise estrogenic activity and affect hormonal systems during that window.
Does a closed window mean adults cannot change? Show answer
No. Adults keep learning, can improve a stutter with therapy, and Linden notes that relief from psychiatric conditions involves plasticity.