> Measure changes in something the test subject isn't expecting and wouldn't realize they need to fake? E.g. if you had to sit in the waiting room for 5 extra minutes, your test score changes like this.

I can discard this by saying "well, the subject might behave subconsciously differently when they know they are in any experiment". How would you refute that?

> Measure differences below conscious control, like reaction speed to positive/negative/etc words after exposure to certain inputs.

What if there are phenomena that don't correlate with the differences you know to measure?

This is too vague. Hiw would you test this hypothesys, that this stidu is teating, by measuring such unrelated signals?

Perhaps this hypothesis simply is harder to test scientifically. It seems lots of claims in psychology are not verifiable.