Glossary
Practice effect
Definition
The practice effect is the rise in test scores that comes from having taken the same or a similar test before. On cognitive ability tests, a retake raises scores by about a quarter of a standard deviation on average, roughly 4 IQ points, and more when the same form is reused.
Want your own number? The test is 25 visual puzzles, about 12 minutes, no sign-up.
What the research found
A meta-analysis of retesting on cognitive ability tests found that scores rose by about a quarter of a standard deviation on average, roughly 4 IQ points, with larger gains when the identical form was reused (Hausknecht et al., 2007).
Why it matters for IQ scores
Practice effects are why a retest is not a clean second measurement. If your score rises by a few points on a second attempt, some or all of that can be familiarity rather than a change in ability. It also means a first attempt may slightly understate someone who has never seen this kind of puzzle. Reading a worked example of each puzzle type before a real test removes much of that surprise.
An example
Someone scores 108 on a first attempt and 112 on a retake with the same items a week later. A gain of that size is in line with the practice effect alone, and it also sits inside a typical confidence interval. The honest reading is “around 108 to 112”, not “my IQ went up 4 points”.
Common confusions
Practice effects are not cheating, and they do not mean tests are meaningless. They are one more reason to read a score as a range. See reliability, how to prepare for an IQ test and does retaking an IQ test raise your score?
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 three outlined stars (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 (circle, star and diamond) exactly once.
- Every row and every column contains each number of shapes (three, two and one) exactly once.
- The fill (outline) stays the same in every tile.
- Check the rules on the second column, then apply them to the third.
- So the missing tile has three outlined stars.
That was 1 puzzle. The full test has 25.
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