A few posts ago I pointed out how Daryl Bem’s Feeling the Future paper (experiments that seem to show the future changing the present) could have been more persuasive. This post is the other side of my critique. I’ll explain why the results are more persuasive than Bem and commentators have said.

If this research is correct, I told my students, you can study for a test not only before but also after you take it. Studying after is better than studying before because you would only need to study what was on the test. And there are reasons to believe the research that Bem didn’t mention:

First, the history of electricity. Electricity, now incredibly important, was once nearly invisible. Remember Galvani? During a frog dissection, an assistant touched an exposed leg-muscle nerve with a static-electricity-charged scalpel. The leg twitched. This tiny accident made all the difference. Galvani studied what had happened. He soon discovered that two different metals in contact generated electricity. This led to the first batteries. With a steady source of electricity, we could learn about it.

The methodological lesson is that the nervous system is (a) unusually sensitive to the environment and (b) easy to “read”. You could touch a static-charged knife to many things: a plant, cloth, a piece of metal, a piece of wood. No doubt this had happened countless times before Galvani. The static electricity changed all of them (plant, etc.) but these changes led nowhere because they were too small to see. In contrast, the effect of static electricity on the nervous system was easy to see. It was amplified by the neuro-muscular junction and the muscle. Measuring the effect of electricity on nerves turned out to be the best way to study it, at first.

My self-experimentation takes advantage of the sensitivity of the brain to the environment. Mostly I study stuff controlled by the brain, such as sleep, weight, and arithmetic speed. Because the brain changes quickly and the changes are easy to detect (via behavior), I can do short convincing experiments. People who study health in other ways have to do much slower and more difficult experiments. For example, bones change slowly in response to dietary changes. Other parts of our body, such as the liver, are much harder to measure than behavior.

The story of how electricity began to be understood suggests that if the future does affect the present, there will be a period when the best way to study this is by studying behavior. This is what Bem did. We don’t normally think of the brain as good for physics experiments but Galvani showed the truth of this. The brain acts as an enormously sensitive amplifier. For example, Barbara Sakitt did an experiment suggesting that the eye can detect single photons. Bem’s experiments cost essentially nothing. He needed no grant. For a physicist to build a detector that detects future effects on the present without involving the brain will surely be more expensive and more difficult, just as it was so much easier for Galvani to use frog legs than build a electricity detector not involving the nervous system.

Second, the history of psi research. Unfortunately Bem omitted even a brief summary from his article. Experiments similar to Bem’s have been going on for decades. In the 1980s, I visited a lab near Princeton doing such experiments. I haven’t studied this research but as far as I know they have repeatedly reported small effects. This is what has kept them going — or at least I cannot rule out this explanation for why it has lasted so long. The alchemists pursued fruitless research a long time but I am unaware they reported small successes. Bem used his knowledge of mainstream psychology (e.g., priming) to design much more sensitive experiments. So it makes sense that these weak effects would become more detectable.

Third, gravity/time symmetry. Bem says we see no signs of the future affecting the present in everyday life. I am less sure. The effects of gravity and time reversal (time going backwards) are remarkably similar. If you watch the same video played forwards and backwards you can tell which is forward (correct) and which is time-reversed: In the time-reversed version, impossible things happen. A man slowly drinks coffee. Correct version: the level of coffee in his cup slowly gets lower, as the coffee goes into his mouth. Time-reversed version: the level of coffee in his cup slowly gets higher, as the coffee comes out of his mouth into the cup. That’s impossible! You can spit again and again into a cup, sure, but you can’t spit pure coffee into a cup. You can’t unmix the coffee from the rest of the liquid in your mouth.

Imagine two billiard balls on a frictionless perfectly flat pool table. They are together in the center. Touching, but not held together. A video of the balls would show them slowly moving apart in response to random disturbances. They move down a probability gradient: Further apart is more likely than close together. This is why a sodium pump is needed to keep enough sodium in cells: because the difference in concentration (more sodium within a cell) makes diffusion out of the cell more likely than diffusion into the cell.

Now we do something different: we randomly and independently place both balls on the table. The placement of one has no effect on the placement of the other. Almost surely they will not be touching. Then we start filming. And a funny thing happens: the balls move closer and closer together! The opposite of the first film, where they slowly drifted apart. They are drifting closer and closer together because they are so heavy that the gravitational attraction is larger than the random forces (e.g., air molecules) in the situation. The second film run backwards looks exactly like the first film run forward! In this way the force of gravity causes time to go backwards. It causes seemingly less-probable events to be more probable than seemingly more-probable events. Rather than have two concepts (force of gravity, passage of time) perhaps we only need one.

I will write more about this later. The simple point is that the effects of gravity are very similar, perhaps identical, to time moving backwards. The force of gravity is obvious and the similarity to backwards time unexplained. Given this failure to explain something easy to see, we shouldn’t be sure we know if the future can visibly affect the present. If time goes backwards to some extent (measured by the force of gravity) then to some extent the future has happened and we know something about it. The more we know about it, the better we can choose to study for a test by studying just the items that will appear on it.