How accurately does self-reported intelligence reflect psychometrically measured IQ?

Studies have demonstrated that people's self-reported intelligence (SRI) is only weakly correlated with their psychometrically measured IQ, which challenges the idea that asking someone how intelligent they are can serve as a reliable proxy for formal ability testing. Data collected from a large sample of Estonian schoolchildren aged 7 to 18 years (N = 4544) showed that only by around age of 10 do children's cognitive abilities develop to a level that allows them to make reasonably accurate self-assessments, as measured by the Raven Standard Progressive Matrices (RSPM). We conclude that meaningful comparisons of one's intellectual abilities with those of peers are only possible once general cognitive development has reached a stage of reflective intelligence, capable of using formal operations and aligning mental concepts with reality. One way to improve the agreement between the SRI and IQ test scores is to increase the reliability of subjective ratings, either by using more items or by enhancing inter-item correlations. However, this agreement has an upper limit, as discrepancies remain between psychologists' definitions of intelligence and lay conceptions, which often conflate intelligence with self-esteem and other unrelated constructs.