The SAT, ACT, IQ tests, and all standardized test like them are socially constructed concepts that ATTEMPT a method of measuring intelligence. Intelligence (in the real world) reaches far beyond one's abilities to answer multiple choice reading comprehension, basic math and writing. Not to mention that problem solving in the real world has no time constraints.
Beethoven would not have gotten a perfect score on his SAT's. However, we all can attest to his innovation, creativity and musical genius. How can a multiple choice test measure the creative abilities of people like Sir Richard Branson, Steve Jobs, or Pablo Picasso?
The idea that "smarter people... were slightly more vulnerable to common mental mistakes" is a nonsensical conclusion. These findings are completely worthless.