The question of the constancy of IQ is not settled; further studies with regular intervals and repeated tests of the same cases over a number of years are needed¶

Claim · All claims
Evidence · 1 study · associational r1 · q1
Currency · newest study 1921 · not yet checked against its sources · not reviewed by a person

Subclaims¶

q1 i? The author explicitly does not assume the question of IQ constancy is settled, calling for further studies covering regular intervals and repeated tests of the same cases over a number of years. → Poull 1921

Evidence¶

Poull 1921¶

Poull, L. E. (1921). Constancy of the I.Q. in mental defectives according to the Stanford revision of Binet tests. Journal of Educational Psychology, 12(6), 323–324. https://doi.org/10.1037/h0071851

q1 · i? · associational · r1

The author's own stated limitation of the present single-institution retest study, offered as an interpretive caution rather than a tested result; no effect size or test statistic is printed for this statement.

"It is not assumed, however, that the question of the constancy of I. Q. is settled until further studies have been made covering regular intervals and including repeated tests of the same cases over a number of years."

Discussion¶

Related Claims¶

• IQs obtained by dividing mental by chronological age remain fairly constant up to the age of 14, which supports treating yearly increments of intelligence as equal absolute units up to about age 14. — related
• Large IQ differences in this sample were mostly attributable to identifiable causes such as failures of previously passed tests, chance success, effort fluctuation, or lack of experience — related
• Repeated Stanford-Binet testing of summer-school pupils over four years shows mostly small IQ differences, with a median difference of 5.25 points — related
• Children whose low first IQs reflected linguistic or environmental deficiency showed substantial IQ gains after gaining command of English or schooling — related
• IQ is only approximately constant across successive examinations, with first-to-fifth IQ correlation of +0.82 and prediction error of 4 to 7 points — related
• Clinic cases retested within less than a month to 15 months show a median IQ difference of 3.5 points, with only four cases above 5 points — related
• The reviewer reports that Baldwin's repeated examinations show the IQ is fairly constant though subject to fluctuations, and that repeated examinations exhibit a definite practice effect — related
• A large percentage of retested cases show IQ variations large enough to change their classification, demonstrating the injustice of disposing of persons on the basis of a single test — a narrower finding that bears on this claim