For IQ: maybe you could nudge people to greater honesty by splitting up the question: (1) have you ever taken an IQ test with [whatever features were specified on this year’s survey], yes or no? (2) if yes, what was your score?
Also, “ever” might be a bit too long. IQs and IQ tests can change over time, so maybe you should ask “have you taken an IQ test [with constraints] in the last 10 years?”
For IQ: maybe you could nudge people to greater honesty by splitting up the question: (1) have you ever taken an IQ test with [whatever features were specified on this year’s survey], yes or no? (2) if yes, what was your score?
Also, “ever” might be a bit too long. IQs and IQ tests can change over time, so maybe you should ask “have you taken an IQ test [with constraints] in the last 10 years?”