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Psilocybin and Reaction Time

Created: 2020-12-04
Wordcount: 1.2k


Reaction time is probably g-loaded. That is, the speed with which you react to stimuli probably correlates with your general intelligence.

Jensen of course has multiple articles on the subject, of which the 1982 "Reaction Time and Psychometric g" seems like the cleanest introduction.

There's further correlational relationships.

For instance, many of the above sources mention how there's stronger correlation between intelligence and reaction time when the reaction involves choice (quickly distinguishing between multiple alternatives in response to an input) than there is between intelligence and reaction time when the reaction does not involve choice (simply hitting a button as fast as possible after a stimulus). There's also stronger correlation between reaction time and intelligence in older groups.

And of course you have to ask why you'd find this correlation at all.

Anyhow -- the above evidence, which is pretty good for the realm of psychology, I thought it would be interesting to test whether psilocybin increased the speed of reaction time. Psilocybin has been hypothesized to improve intelligence, creativity, or openness in many ways. If it increases reaction time, this could then be construed as evidence supporting the hypothesis that it increases intelligence, creativity, or openness.

(I'm of course aware that it's possible for psilocybin to improve reaction time without increasing intelligence or creativity, just as it's possible for it to increase intelligence or creativity without improving reaction time. On balance, though, if it improves reaction time, I'd take that to be moderate evidence in favor of other positive effects.)

Self-experimentation that involves taking a full intelligence test is hard. Intelligence tests take a while to take, and are hard to obtain. Self-experimentation that involves testing reaction time is easy. These can be taken quickly and are easy to create.

So, the basic n=1 experiment involved testing my reaction time every day for some time, taking some psilocybin, and testing my reaction time every day for some time afterwards.


For a reaction-time test, I made a quick JS app.

You click the screen to prime it; the background switches to green, and it displays text telling you it will soon change. Some time between 750 and 13000 milliseconds later, the screen changes from green to red and the text changes as well. The app records how long it takes for you to click after this stimulus. For the experiment, I did this 25 times a day for many weeks, and recorded the min, max, mean, and median of each time I did it.

(In retrospect, the experiment would have been much better if I recorded every single click time, rather than just the min, max, mean, and median. The evidence would likely have come out stronger either way. I would say live and learn; but I knew that this would be so antecedently as well. I was merely lazy.)

This reaction time test I took is different from other online reaction time tests in at least two ways.

  1. There's a 12250 millisecond window where the event can occur, which is larger than most other windows.

  2. I weighted the event so that it occurs more frequently towards the beginning of the window than at the end. This was chiefly because I noticed that, with an even chance of the event occurring at any point in the window, I relatively frequently (1 / 30 cases?) knew that the window was ending soon and could "anticipate" the event, resulting in cases where I "reacted" in less than 100 milliseconds, which is impossible. The weighting helps avoid this.


I had to discard some of the pre-intervention data that I had collected.

I was using a wireless mouse as my peripheral. Unfortunately, I realized it was very probably introducing lag and variability into the data -- one day when I was not using the wireless mouse I realized I was consistently faster. So I had to discard a big chunk of data after switching peripherals.

We can use this data to gently poke at the hypothesis that I would get better at the reaction test simply by practice. So, for instance, are 26 days of my average reaction time in milliseconds, using the wireless mouse as my peripheral:


If we divide the data into two sets of 13 days rather arbitrarily, we find that the mean of the second 13 days is actually higher than the mean of the first 13 days. (They are not different at p < 0.05 by two-tailed t-test.) So it seems unlikely that I was getting much better simply through practice normally.

Additionally, the two means of 257.8 and 265 provide a smell test. If my mean performance does not improve by notably more than this drop in performance, it's going to be hard to attribute it to the intervention.


I took the reaction test with the same wired peripheral mouse every day for 13 days. I then took 1.5 grams of dried cubensis using lemon-tek, in a location where such substances are legal. I then took the same reaction test with the same wired mouse every day for the following 13 days.


Here are the averages before the intervention:


And here are the averages after the intervention:


They are pretty interesting results. The mean time dropped from about 239 to 225, a decrease of 14ms. We have significance for the two-tailed t-test at p < 0.01, although not p < 0.001.

Out of curiosity, I also threw the medians / mins / maxes into the t-test. They all differ by p < 0.05, although only the maxes differ by p 0.01. I'm not really statistically literate enough to know what this means for weird values like the min / max.

Considerations & Further Research

It seems possible, although not certain, that psilocybin had some effect on my reaction time, and potentially also on my intelligence. Here are some potential scenarios where the psilocybin had an effect.

  1. Psilocybin directly changed some aspects of my brain function, which resulted in better reaction time, apart from any deliberate practice on the reaction time test.

  2. Psilocybin increased my brain's plasticity, which empowered deliberate practice on the reaction time test. This hypothesis is distinguished from the first because in this hypothesis, it is the practice which directly improves reaction time, while in (1) the psilocybin directly increases performance on the reaction-time test unmediated by practice. Part of me inclines to this hypothesis, because it seems the most moderate in the effects it attributes to psilocybin. Even so, I don't think the evidence really supports it. On this hypothesis, you'd think that I would start at about the same performance and gradually improve, but the data doesn't really look like that.

Here are some potential scenarios where the psilocybin had no effect.

  1. I tried harder after the intervention. The improved reaction times are a result of trying harder.

  2. Some other practice in my life improved my reaction time. I was meditating and playing a fair amount of a very twitchy video game around this time. It nevertheless strikes me as very implausible that these would suddenly start having an effect at just the same time as the pharmaceutical intervention, because neither started at the same time as the intervention.

I think, overall, it's more notably more likely that psilocybin had an effect than not. Nevertheless, further research is needed.