<p>A high score represents a very large number of hours spent reading, learning, thinking, and doing schoolwork. "3 hours of one's life" is the rhetoric of SAT-haters.</p>
<p>Across-the-board perfect scores (one-shot results of 1600 SAT, 800's on subject tests, 5's on AP's, etc) certainly have some psychological impact. They leave no room for speculation except as to just how far off the top of the SAT/ACT/AP scale the candidate is. The whole is greater than the sum of its parts, in that each further perfect score reinforces the correctness of the others, whereas with one or two tests it could have been preparation or luck. </p>
<p>Perfect old-SAT when only about 300 people a year achieved it, would certainly have been a "hook". Perfect SAT or ACT today puts you in a pool of several thousand, and many more thousands considering the variation in scores. I think in both cases some additional 800's would be needed to remove doubt that 1600 is the correct measurement.</p>