Myth 1 — There is a fixed genius threshold
Numbers like 140 or 160 are conventions, not discoveries. Because the standard deviation differs between tests, a '140' on one instrument can be a '132' on another with no change in the person.
Historical IQ estimates for famous figures are worse still: they were reconstructed from biographical anecdotes long after the fact, by researchers who already believed the subjects were exceptional.
Myth 2 — We only use 10% of our brains
Functional imaging shows activity distributed across the entire brain over the course of a day, and there is no dormant reserve waiting to be unlocked. Damage to almost any region produces deficits, which would be impossible if most tissue were idle.
The myth persists because it sells a comforting story about untapped potential. Real cognitive gains come from learning and health, not from unlocking spare capacity.
Myth 3 — IQ is fixed at birth
Twin and adoption studies show substantial heritability of intelligence in adulthood, but heritability describes the share of variation within a population under its current conditions. It does not mean an individual's score is immovable, and heritability estimates themselves rise with age and vary with socioeconomic conditions.
Longitudinal studies that retest the same adolescents years apart find that a meaningful minority shift by ten points or more in either direction, with corresponding changes in brain structure. Environment, schooling, and health do real work.
Myth 4 — Online tests are worthless
A well-constructed online matrix test with calibrated items and honest reporting gives a reasonable estimate of fluid reasoning, and correlates respectably with supervised measures. It is genuinely useful for curiosity and self-insight.
What it cannot do is deliver a clinical result. It is unsupervised, its norms come from self-selected visitors, and nothing prevents distraction, retakes, or outside help. The failure mode is not the format but the overclaiming: any site presenting an online estimate as a diagnosis is misleading you.
Myth 5 — Creativity and IQ are unrelated
They correlate positively but weakly, and the relationship appears to be threshold-like: above roughly average-plus ability, further increases in IQ predict little additional creative achievement, while openness to experience, motivation, and domain knowledge predict a lot.
In other words, reasoning ability is closer to a ticket of entry for creative fields than to an explanation of who produces original work within them.
Myth 6 — A Mensa-level score guarantees success
Long-term studies of intellectually gifted children — including Terman's cohort followed for decades — show above-average educational and occupational outcomes on average, alongside an enormous spread of individual results, including people who were unhappy, unemployed, or simply ordinary.
Conscientiousness, social support, health, opportunity, and luck all carry weight comparable to or greater than test scores in predicting how a life actually goes.
Myth 7 — IQ peaks at 25 and declines from there
Different abilities peak at different ages. Processing speed does peak in the mid-twenties and declines slowly thereafter. Working memory holds up longer. Vocabulary and accumulated knowledge often keep improving into the sixties or beyond.
Because a full-scale score averages these trajectories, the composite looks flatter than any of its parts. What changes with age is the profile, not a single quantity draining away.