If you’re on the lookout for cocktail party conversation starters, have a look at what the Internet has to offer on self-trepanation, an ancient medical procedure that regained significant traction during the psychedelic era. Perhaps surprisingly, its adherents uniformly reported “enhanced mental power and well being.”

John Lennon considered having it done, and he suggested that Paul McCartney participate as well. As McCartney later recalled,

“We’d all read about it — you know, this is the ‘60s. The ‘ancient art of trepanning,’ which lent a little bit of validity to it because ancient must be good. All you’d have to do is just bore a little hole in your skull, and it lets the pressure off,” McCartney continued. “Well, that sounds very sensible. ‘But look, John, you try it and let me know how it goes.’ The good thing about John and I — I’d say no. And he knew me well enough that if I said no, I meant no. I’m not frightened of being uncool to say no. I wouldn’t go far as to say, ‘You’re f***ing crazy,’ because I didn’t need to say that. But, no, I’m not gonna trepan, thank you very much. It’s just not something I would like to do.”

In Bore Hole, re-issued in 2015 by MIT Press (in a heavily expanded edition) Joe Mellen describes the difficulties that he encountered during his abortive first attempt at self-trepanation:

I was living back in London, and it was 1967. At that time, I was broke, and I certainly couldn’t afford an electric drill, so I bought a hand trepan from a surgical instrument shop. It’s a bit like a corkscrew, really, but with a ring of teeth at the bottom. It has a point in the middle, which makes an impression on the skull, and then you turn it until the teeth cut into the skull. It’s slightly narrower at the bottom than it is at the top, so it pulls the circular piece of skull out once you’re through with it when you pull it out. It was difficult. It was like trying to uncork a bottle of wine from the inside. The trepan was blunt, and I couldn’t get any purchase on my own skull. I was tripping on acid. I thought that it was the only way I could get through doing it, but it didn’t work…

I came across that passage more than thirty years ago. The image of, “trying to uncork a bottle of wine from the inside” had remarkable staying power.

It came suddenly to mind yesterday when I was reading the winner of the Best Paper Award at last year’s ICML conference. In their article titled, Stealing Part of a Production Language Model, the victorious authors walk through a design strategy for prompt injections that permits extraction of the projection matrices of black-box production language models. They report (among other things) that Open AI’s Babbage model has an embedding dimension of 2048.

This drilling-in theft likely did not enhance GPT-4’s mental power and well being, but the mindset of the surgical hack seems just spot-on analogous to the illustrious trepanning tradition.