Just reading the Amazon summary, I feel like there’s a contradiction. If subjects were just trying to get it over with, yes it invalidates the study but the only troubling conclusion is that the study wasn’t scrutinized more closely.
I also don’t see why they would be “haunted” by what effectively amounts to a chore to get their $20 participation check.
And social science/history/economics is about learning the standard lessons of the field (even if those lessons are themselves simplistic compared to the real world, they are a baseline of common knowledge).