Symbolism, Imagery, Allegory
What the heck does a Rorschach test stand for anyway? Charlie's initial belief that there are "pictures in the ink—that everyone could see…" (57) changes drastically when he realizes that the test is designed to measure his intelligence. Charlie's ability to make meaning is a crucial part of his new abilities.
Before Charlie undergoes surgery, he believes that everyone can see the same pictures in the inkblots. He's baffled when Burt tells him otherwise: "You mean there are no pictures hidden in those inkblots?" (56). That's because intelligence isn't distributed equally. More than merely being smart, Charlie doesn't want to be the only one who doesn't get it.
The inkblots show not only how much Charlie wants to be smart, but also his belief that everyone else is already smart. At least at first, Charlie thinks of intelligence as something people are just owed—you're born and you get smarts handed out to you like Halloween treats. As Charlie undergoes surgery and starts to learn a bit, his views change radically—all of a sudden, what matters more is how much smarter he can be than everyone else if he puts his mind to it.
Right before Charlie cuts the cord and doesn't go back to Beekman, he goes through one last Rorschach test. Even though Charlie has memories of taking the test correctly, he just can't figure it out: "I know the kind of responses I'm supposed to have, to create a certain picture of what my mind is like. All I've got to do is…" (17.287). And nothing. Seeing the inkblots is even more frustrating because it's a reminder that he used to be a wiz kid—now even armed with the knowledge needed to game the test, Charlie is helpless.