Intelligence

Intelligence is an interface between physiology and the environment, so it's necessary to think about each aspect in relation to the other. Things, both biochemical and social, that enhance intelligence enhance life itself, and vice versa.

— Ray Peat

Intelligence isn't a fixed trait; it tracks metabolic capacity directly, and the same biochemical and social factors that raise or lower it also raise or lower general health.

Stress, serotonin, and development

Appropriate stimulation is an essential part of healthy development; inappropriate stimulation is itself a stress that deforms the growth process, working through the same mediators, serotonin chief among them, that produce lasting distortions of physiology and behavior elsewhere on this wiki. Early-life stress specifically impairs learning and can produce aggressive or compulsive behavior, learned helplessness, shyness, or alcoholism later on.

Serotonin activates the glucocorticoid system, which can cause brain atrophy; excess serotonin over time also raises thrombosis and vasospasm risk, and the resulting excess cortisol weakens blood vessels and the immune system, shortening lifespan unless something intervenes. Pregnenolone and progesterone protect against this: both are brain-protective neurosteroids, both rise with the right kind of stimulation, and both fall under isolation stress, leaving serotonin and glucocorticoids relatively unopposed when that happens.

Hormones, gestation, and brain growth

Brain size and learning ability aren't fixed by "the genes" independent of the organism's chemical environment. When researcher S. Zamenhof opened chicken eggshells at the developmental stage when brain growth normally stops and added glucose, the brain kept growing, producing chickens with measurably bigger brains; treating pregnant rats to raise progesterone had a parallel effect, producing offspring with bigger brains that learned more efficiently.

Marian Diamond's work with rats found the same hormonal split in the other direction: more estrogen exposure during pregnancy reduced cerebral cortex size and learning ability, while progesterone increased both brain size and intelligence, probably largely through effects on glucose and oxygen availability to brain cells. In humans, Katharina Dalton's patients, given progesterone throughout pregnancy to prevent toxemia, had children who were "remarkably healthy and bright"; the average baby born after an untreated toxemic pregnancy has an IQ of about 85, against an average of about 130 in Dalton's progesterone-treated group. Peat considered this a fair estimate of what proper prenatal care could do at a population scale, on top of the other benefits of a healthy gestation: strength of character, capacity for abstract reasoning, and freedom from physical defects all track with it as well, not IQ alone.

Postnatal nutrition shows the same pattern. A comparison of undernourished children against well-nourished children, controlling for parental intelligence, found a 22.6-point IQ difference favoring the better-nourished group. Later timing in development matters too: generalizing from animal studies, delaying puberty appears to increase brain size, longevity, and intelligence, and to decrease violence.

Education: activating or suppressing mental energy

Education can either activate mental energy or suppress it, depending entirely on its form. Obedience training suppresses it; schooling that creates real social dislocation disturbs mental and emotional energy instead of building it.

Summerhill, a democratic school founded in 1921 that gave children real freedom over their own time and learning, ran directly counter to conventional obedience-based schooling and was still under government threat of closure decades later, despite government inspectors themselves recommending in 1927 that "all educationalists" study its methods. Rat studies point the same direction physically: a brain measurably adapts to the level of stimulation in its environment, and play, curiosity, and peer interaction all raise intelligence, while isolation lowers it.

Prodigies and isolation

Intellectual lineage often runs through direct mentorship as much as genetics: Jeremy Bentham was John Stuart Mill's godfather, Mill was Bertrand Russell's; Ralph Waldo Emerson was William James's godfather. William James Sidis was raised by his parents specifically to demonstrate an educational theory descended from Emerson and James: he learned several languages and advanced mathematics as a young child and graduated Harvard at 16, but the isolation and public mockery that followed him through Harvard and Rice Institute, worsened by antisemitism, left him with a much shorter and more troubled life than his early promise suggested. Sidis and John Stuart Mill (subjected to a similarly intense, isolated early education by his own father) both illustrate the same pattern: pressure and isolation in childhood can produce genuine intellectual power alongside real psychological damage and a shortened lifespan, not because intelligence itself is dangerous, but because the isolation that often accompanies extreme early achievement is.

On IQ testing

IQ tests capture only part of what intelligence actually is, since intelligence itself is metabolic and changeable rather than a fixed quantity a single test could measure once and for all. Stimulating environments raise measured IQ; poor, understimulating schooling lowers it, consistent with the same metabolic and environmental interface that runs through the rest of this page.

A randomized trial of 144 six-year-olds tested this directly: children given a year of weekly keyboard or vocal lessons gained an average of 7.0 IQ points, against 4.3 points for children given drama lessons or no lessons, with the music groups ahead on nearly every IQ subtest measured.

Population-level IQ isn't a one-way ratchet either. Norwegian conscription data on over 730,000 men found test scores rising through the 1975 birth cohort (the "Flynn effect") and then declining afterward by about 0.2 points per year; because the decline showed up between brothers in the same families, it can't be explained by genetics or immigration and points to a changing environment instead. Similar reversals appear in Denmark, Finland, France, and the UK from roughly the mid-1990s on.

Fostering intelligence

The practical throughline is freedom, empathy, and variety, both for brain function directly and for reducing the violence and compulsive behavior that early stress and isolation otherwise produce. Where cultural stresses can't simply be removed, the same chemical supports used elsewhere against stress, thyroid, anti-serotonin agents, protective neurosteroids, work here too.

See also

• Learned helplessness
• Serotonin
• Progesterone
• Pregnenolone
• Stress
• Bioenergetics
• Creativity
• Pregnancy