“Surely You’re Joking, Mr. Feynman”: Adventures of a Curious Character

“Isn’t it true that you’re supposed to get hallucinations under those circumstances?” I asked, excitedly.

“That is true indeed.”

I had always had this fascination with the images from dreams and other images that come to the mind that haven’t got a direct sensory source, and how it works in the head, and I wanted to see hallucinations. I had once thought to take drugs, but I got kind of scared of that: I love to think, and I don’t want to screw up the machine. But it seemed to me that just lying around in a sense-deprivation tank had no physiological danger, SO I was very anxious to try it.

I quickly accepted the Lillys’ invitation to use the tanks, a very kind invitation on their part, and they came to listen to the lecture with their group.

So the following week I went to try the tanks. Mr. Lilly introduced me to the tanks as he must have done with other people. There were lots of bulbs, like neon lights, with different gases in them. He showed me the Periodic Table and made up a lot of mystic hokey-poke about different kinds of lights that have different kinds of influences. He told me how you get ready to go into the tank by looking at yourself in the mirror with your nose up against it—all kinds of wicky-wack things, all kinds of gorp. I didn’t pay any attention to the gorp, but I did everything because I wanted to get into the tanks, and I also thought that perhaps such preparations might make it easier to have hallucinations. So I went through everything according to the way he said. The only thing that proved difficult was choosing what color light I wanted, especially as the tank was supposed to be dark inside.

A sense-deprivation tank is like a big bathtub, but with a cover that comes down. It’s completely dark inside, and because the cover is thick, there’s no sound. There’s a little pump that pumps air in, but it turns out you don’t need to worry about air because the volume of air is rather large, and you’re only in there for two or three hours, and you don’t really consume a lot of air when you breathe normally. Mr. Lilly said that the pumps were there to put people at ease, so I figured it’s just psychological, and asked him to turn the pump off, because it made a little bit of noise.

The water in the tank has Epsom salts in it to make it denser than normal water, so you float in it rather easily. The temperature is kept at body temperature, or 94, or something—he had it all figured out. There wasn’t supposed to be any light, any sound, any temperature sensation, no nothing! Once in a while you might drift over to the side and bump slightly, or because of condensation on the ceiling of the tank a drop of water might fall, but these slight disturbances were very rare.

I must have gone about a dozen times, each time spending about two and a half hours in the tank. The first time I didn’t get any hallucinations, but after I had been in the tank, the Lillys introduced me to a man billed as a medical doctor, who told me about a drug called ketamine, which was used as an anesthetic. I’ve always been interested in questions related to what happens when you go to sleep, or what happens when you get conked out, so they showed me the papers that came with the medicine and gave me one tenth of the normal dose.

I got this strange kind of feeling which I’ve never been able to figure out whenever I tried to characterize what the effect was. For instance, the drug had quite an effect on my vision; I felt I couldn’t see clearly. But when I’d look hard at something, it would be OK. It was sort of as if you didn’t care to look at things; you’re sloppily doing this and that, feeling kind of woozy, but as soon as you look, and concentrate, everything is, for a moment at least, all right. I took a book they had on organic chemistry and looked at a table full of complicated substances, and to my surprise was able to read them.

I did all kinds of other things, like moving my hands toward each other from a distance to see if my fingers would touch each other, and although I had a feeling of complete disorientation, a feeling of an inability to do practically anything, I never found a specific thing that I couldn’t do.

As I said before, the first time in the tank I didn’t get any hallucinations, and the second time I didn’t get any hallucinations. But the Lillys were very interesting people; I enjoyed them very, very much. They often gave me lunch, and so on, and after a while we discussed things on a different level than the early stuff with the lights. I realized that other people had found the sense-deprivation tank somewhat frightening, but to me it was a pretty interesting invention. I wasn’t afraid because I knew what it was: it was just a tank of Epsom salts.