Can IQ change over time?

IQ scores can and do change. Test-retest reliability is high but not perfect — typical correlations between two administrations of the same test are 0.85 to 0.95. Within an individual, scores can shift by 5 to 10 IQ points between administrations due to measurement error alone, and by larger amounts due to changes in test conditions, motivation, sleep, or the test-taker's underlying cognition. Larger shifts in measured IQ across years of life are documented, especially in adolescence (when frontal-lobe development is still ongoing) and in old age (when cognitive decline begins to affect scores). The most actionable interpretation is that your IQ is reasonably stable across the medium term but is not a fixed property of your brain.

This question comes up frequently from users of free online IQ tests and from people considering whether to pursue a clinical evaluation. The full answer depends on context — what the score will be used for, how recently the test was administered, and what other information is available. The brief answer above captures the broad consensus from the published research literature; the linked deep-dive articles cover the underlying evidence in more detail.

Related considerations include the standard error of measurement on the relevant test, the population the test was normed against, and the specific cognitive abilities the test samples. A score is much more informative when interpreted alongside these contextual variables than when reported as a bare number.

If this answer raises further questions, see the related FAQ entries listed in the sidebar and the longer-form articles on the same topic in the article library. The site is designed to provide layered depth: the FAQ entries offer concise answers, the deep-dive articles offer the underlying research, and the score-interpretation pages tie the abstract concepts to specific result bands.