Question
Does retaking an IQ test raise your score?
Short answer
Usually, yes, a little. A meta-analysis found that retaking a cognitive ability test raises scores by about a quarter of a standard deviation on average, roughly 4 IQ points, and more when the exact same form is reused. Most of the gain comes from familiarity with the format, not from a change in ability.
Want your own number? The test is 25 visual puzzles, about 12 minutes, no sign-up.
The size of the practice effect
Hausknecht and colleagues pooled retest studies of cognitive ability tests and found an average gain of about a quarter of a standard deviation, roughly 4 IQ points on the usual scale (Hausknecht et al., 2007). Gains were larger when people saw the same form again. In plain terms: the second time, you know the item types, the pace and the traps.
Try one · Abstract Reasoning
Which tile completes the grid?
Tap the option you think is right, or show the answer.
Show the answer
The missing tile has a large solid square (option 8).
How to solve it
- Start with the first column and name what changes from tile to tile.
- Every row and every column contains each shape (square, pentagon and cross) exactly once.
- Every row and every column contains each fill (hatched, solid and outline) exactly once.
- The size (large) stays the same in every tile.
- Check the rules on the second column, then apply them to the third.
- So the missing tile has a large solid square.
That was 1 puzzle. The full test has 25.
Why it is not a real rise in ability
Nothing about your reasoning has to change for a retest score to rise. The first time through, part of your effort goes into figuring out what the test wants. The second time, that effort goes into the puzzles. That is why the effect is biggest when the same questions come back: some of the gain is plain memory.
The gain is also about the same size as ordinary measurement error. Clinical manuals often report a confidence interval of around plus or minus 5 points at 95% (Wechsler, 2008), so a 4-point change between two tests may be noise.
How to use this
- If you want your first score to reflect your ability, get familiar with the format first. A few practice puzzles remove most of the surprise.
- If you retest, do not read a few points of change as a real change.
- Prefer tests that do not reuse the same items. On IQ Octopus every attempt gets newly generated puzzles.
The glossary entry on the practice effect has the definition, and can you increase your IQ covers what practice can and cannot do.
Sources
- Hausknecht, J. P., Halpert, J. A., Di Paolo, N. T., & Moriarty Gerrard, M. O. (2007). Journal of Applied Psychology, 92(2), 373-385. doi.org/10.1037/0021-9010.92.2.373
- Wechsler, D. (2008). WAIS-IV Technical and Interpretive Manual. Pearson.
- Estevis, E., Basso, M. R., & Combs, D. (2012). Effects of practice on the Wechsler Adult Intelligence Scale-IV across 3- and 6-month intervals. The Clinical Neuropsychologist, 26(2), 239-254. doi:10.1080/13854046.2012.659219 pubmed.ncbi.nlm.nih.gov/22353021/
- American Mensa. Admission testing. www.us.mensa.org/join/testing/