Oooh. I like this.
My take is an alternate version of Strange Visitor: The lie detector indicated that Clark Kent was telling the truth when he answered that he was Superman. Clearly, this glasses-wearing reporter couldn't possibly be Superman, and yet he believed himself to be. After verifying that the lie detector was working properly -- and even trying again with a different lie detector -- it was determined that Kent did, indeed, hold this obviously-counterfactual belief.
Rather than putting those close to him in danger by revealing the truth, Clark permitted himself to be committed and wound up going to the same facility in which Wandamae Waldecker was a patient.
While there, he taught himself how to control his body's functioning in such a way that he could pass a subsequent lie detector test and he faked out the attending psychiatrists so that they believed him "cured" and he was eventually released.
