Actually, many of these tests are empirically based and the items have low face value e.g., (MMPI). In addition they have "lie keys" that detect efforts to cheat or fake.
Actually, the field of psychological testing is pretty hitech, fellow redneck.
PET brain scans might have promise in revealing what topics actually raise the most interest in the test subject. For everything else, the subject just needs to make up his mind about who he will “be” and follow through on it.