Quitting coffee attracts some attention!

Week 1 coffee report

Coffee Beans
Image by Refracted Moments™ via Flickr

This past Tuesday marked one week on my new, randomized plan to quit coffee.  In case you missed that post, the plan-in-a-nutshell is this: I supply my wife Erin with the coffee beans I will use for the week, starting with 60% regular, 40% decaf, and increasing the proportion of decaf beans each week.  She then portions out each day’s serving, but in so doing, randomizes each day’s ratio, with the only restrictions being that one day must be 100% caffeinated and one day must be 100% decaf.  I then drink coffee normally, never finding out exactly what I drank each day.

I’m happy to report that though it hasn’t played out quite as I had expected, it’s working even better than I had hoped.  The highlights:

  • I stopped trying to guess what I was drinking after the first few days, realizing that it’s nearly impossible for me to tell, based on taste or experience, except perhaps on the 100% days.
  • I have no idea which day was the 100% decaf day.  This is encouraging and is proof that I don’t “need” the caffeine.
  • I think I can point to Monday as the 100% caffeinated day.  Interestingly, I didn’t notice anything until I felt the negative effects (jitteriness, nervousness, anxiety)!  While I was drinking it, I felt the same as every other day.  But in hindsight, I can see that I was perhaps a little happier.
  • I’m noticing that I already crave coffee less, yet I still really enjoy it when I drink it.  Specifically, I’m enjoying what I’ve always associated to drinking coffee: pleasant mood, mild mental stimulation, etc.  But with the exception of the 100% caffeine day, there are fewer negative side effects.
  • On to 40% regular, 60% decaf this week!

Others write about the plan

Two other bloggers, neither of the health and fitness variety, found my coffee experiment intriguing enough to write devote entire blog posts to it!  The first to do so was Andrew Gelman, statistics and political science professor at Columbia University, and author of several statistics textbooks.  You can read what Dr. Gelman had to say about my java-dropping plan in his post A randomized self-experimentation story: A plan to quit coffee.

The second blogger was a psychology student named Michael Griffiths, who took a critical view of the experiment and projected that it might actually backfire, in his post about it.  His main point is summarized here:

If a rat in a cage presses a button, and food comes out sometimes – randomly – then the rat is going to push the button more than under continuous reinforcement, and will also keep pushing the button long after a rat under continuous reinforcement has given up on it. Humans are worse, if anything – they try to create a pattern to predict when the reward will come, even if it’s completely random.So why could Matt’s plan backfire?

Matt’s basically putting himself on a partial reinforcement schedule. He’ll drink a cup of coffee in the morning, and sometimes he’ll receive caffeine, and sometimes he won’t; and the amount of caffeine he receives will vary.

This plan could make him drink more coffee, in the end.

Interesting, huh?  I’ve always liked psychology, but never really took a serious course in it.  I sure hope this doesn’t turn me into even more of a coffee fiend!  The only problem I see with Michael’s analysis is that the mapping from the rat experiment to mine is weak: when the rat gets the food, he knows he gets the food, and his behavior is thereby “reinforced.”  When I drink my mystery coffee, I can only guess at how much caffeine is in it, and without much accuracy.

For all his psychology chops though, Michael doesn’t seem to have a good grasp on the randomness part, a not-uncommon issue for researchers without a strong statistics background (note the Columbia statistics professor took no issue with the randomness!).  Michael writes:

There are also, additionally, other problems – e.g. his wife is randomizing the proportions. The way she randomizes the proportions will be very important, and could have a significant effect on the results (she should use something like Excel to generate really random proportions, and not pseudo-random).

First, the superficial: No machine on Earth produces “really” random numbers, unless it does so by monitoring some truly random atomic event and translates the result into a number.  Programs like Excel start with a seed value (machine time, for example) and perform a complex, but nonetheless logical, series of operations, which results in what appears to be a random number.  Hence the term “pseudo-random,” applied to these types of programs but used incorrectly in the above passage.

The more pertinent point of disagreement, for me, is that the way Erin chooses the random proportions could will have a strong effect on my results, especially if it’s not truly random.  I considered specifying a specific distribution for Erin to use (e.g., should there be a wide variation around the mean or a small one?), and concluded that it really wouldn’t make much difference.  The point is that I don’t know what to expect (and have difficulty distinguishing caffeine from decaf anyway).  So it doesn’t matter if, say, the proportions are almost all exactly 60% caffeine, or if it varies greatly day to day; as long as Erin isn’t acting in such a way that I can detect a pattern, the proportions are random, from my perspective.

Michael’s last line is my favorite, and a gem of a great idea (I even secretly hope Erin reads it, doesn’t tell me, and does as Michael suggests).  I’ll let you go to his post to read it.

Thanks to both Andrew and Michael for writing about my coffee plan.

The biggest question: How did No Meat Athlete, my vegetarian running blog, come to this, a discussion about randomness?  Don’t worry, it won’t happen again soon.  But if you’re a nerd like me who gets off on this stuff, I’ll recommend the book Fooled By Randomness, by Nassim Nicholas Taleb.  If I could point to one book that made me want to go to grad school for math, this would be it.



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  1. I’ve been waiting for an update! When I quit coffee a few years ago I just cut it out completely because I know that if I switched to decaf I would just drink a ton of it to get as much caffeine as I could. Sounds like I wouldn’t have been alone! Keep up the good work!
    .-= Allyson´s last blog ..Madison Kit Giveaway! Blogversary! With a Side of Style Your Knits =-.

  2. Thanks for reading my post!

    A couple of clarifications:

    1) Programs like Excel are still pesudorandom, but I didn’t point it out since (i) they improved the rand() function in 2003 (before 2003, it was so non-random as to be funny) and (ii) the only people who care about how non-random computer generated random sequences are already know about the problem 🙂

    2) The interesting thing about reinforcement is that you don’t need to be consciously aware of the reinforcement. In fact, most aren’t. People also condition on the most abstract things. You ever wonder why people undergoing long-term treatments switch rooms so frequently? Or why hospitals routinely change the furniture and pictures in treatment rooms? (if you didn’t know, they do). It’s because people will get “conditioned” to the “stimulus” of a picture, and it will increase their tolerance to the treatment.

    Fun fact: drug addicts who inject/ingest in the same location sometimes die if they suddenly change locations and use their previous dose. They get conditioned to the place they normally inject – e.g. the smell, the site of a particular couch, the company of people they inject with, etc – and as soon as they walk in that room, their tolerance goes up. That is, their body *knows* it’s going to receive the drug soon, and pre-emptively starts generating chemicals to handle it. Switching to a different location means those chemicals don’t get generated, so their tolerance is effectively lower (sometimes fatally).

    Conditioning – either classical or operant – can occur almost at the cellular level. It’s also almost entirely unconscious.

    The point being that you don’t need to *know* how much caffeine is in the cup, because there’s a chemical reaction in your body regardless – and that’s what reinforces.

    1.5) Because of the potential for inadvertent conditioning, if the caffeine schedule you are on isn’t random – rather, has a defined pattern – you could be conditioned in some way on that. Using Excel (the most obvious answer) would prevent possible confounding. For instance, if you always have a high-caffeine day after a low-caffeine day, you’ll body eventually expect that and actually become conditioned – you might even feel more tired in the morning after a low-caffeine because your body expect the stimulus.

    3) Also, while I can’t really claim to *not* be a psychology “student,” it’s more of a side interest than my focus of study. But no real need to make that distinction

    • Michael, that is fascinating stuff about how the body becomes conditioned even with things we don’t consciously pick up on. I actually thought about whether I might subconciously “notice” a pattern in Erin’s proportions, but as the post got longer and longer, I decided not to include it. My first answer was “no,” but your comment is making me rethink that. In any case, it doesn’t matter, because I realized that there’s no reason to put dates on the bags, and just started grabbing one randomly out of the cupboard each day. That eliminates any temporal pattern that might exist. Still there is the question of whether the type of distribution the randomness takes would impact the results, but I can’t think of any good reason why it would.

      Sorry about calling you a psych student. I saw you like econ too; so do I. Especially its intersection with psychology, like the Kahnemann/Tversky work.

  3. Interesting…I brought this up to my husband who is waaaay too over caffeinated most days. Glad to hear that the first week went well. We may try this soon! I did wonder how he would quit completely & I guess Michael’s last line was the answer. Thanks!
    .-= Michelle´s last blog ..When everyday feels like Groundhog Day… =-.

  4. Ok. So here’s my problem with this experiment. And this is coming from someone who is trying to quit coffee too, but what happens if you started the first day with all decaf, and then worked your way up to fully caffeinated by the end? Although you feel like you’re making progress, you can’t ignore the physiological effects of caffeine withdrawal. You can’t randomize headaches, right?
    .-= sarah´s last blog ..FYI =-.

    • Sarah, good question. I think when you talk about “the end,” you mean the end of a week, right? In that case, yes, it’s possible (but unlikely) that I’d start a week with all decaf and gradually increase caffeine until I get the fully caffeinated coffee on the last day.

      But I don’t think that would be a big deal. Over that week, I would have still averaged exactly the amount of caffeine that was called for. The next week I’d continue reducing the total proportion of caffeinated coffee. I guess it’s possible there would be a headache or something as a result of having a few high-caffeine days in a row, but in my experience, it takes a few weeks of caffeine-drinking for headaches to happen. Even just one day off week prevents them from happening, for me.

  5. Great post! I love this kind of psychology stuff. Good luck with the coffee quitting!
    .-= Caroline´s last blog ..Spring Training Plan =-.

  6. That would be hilarious is Erin tricked you by giving you decaf for the whole experiment… is she sneaky like that? Thanks for the update about it!
    .-= Heather @ Get Healthy With Heather´s last blog ..Turkey and Chickpea Burgers =-.

  7. Great job, Matt! Getting talked about on others’ sites is wonderful. Good luck with the rest of your quitting.
    .-= Nicki´s last blog ..People Pleasing =-.

  8. At work today, I ground some coffee and then got busy with something else. When I came back to it, for the life of me I could not remember which kind I ground. I put it in a ziplock to donate to your experiment. 🙂

  9. I plan to cut out all caffeine in the near future and have quit in the past. I am going to try to avoid the headaches by stepping down over 3 weeks or so. We’ll see.

    Thx Mark

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