Here's another case:

"Let me get this straight. We had sex. I wind up in the hospital and I can't remember anything?" Alice said. There was a slight pause. "You owe me a 30-carat diamond!" Alice quipped, laughing. Within minutes, she repeated the same questions in order, delivering the punch line in the exact tone and inflection. It was always a 30-carat diamond. "It was like a script or a tape," Scott said. "On the one hand, it was very funny. We were hysterical. It was scary as all hell." While doctors tried to determine what ailed Alice, Scott and other grim-faced relatives and friends gathered at the hospital. Surrounded by anxious loved ones, Alice blithely cracked jokes (the same ones) for hours.

I wish it was professionally ethical for psychologists to do this kind of thing intentionally.

They could probably do some relevant research by talking to Alzheimer's patients - they wouldn't get anything as clear as that, I think, but I expect they'd be able to get statistically-significant data.