Experience vs Evidence

The most difficult thing in the world is convincing someone that their experiences are not reliable proof of anything.

I know what happened.     I remember it perfectly!     I know what I saw.

The unfortunate truth is that for a surprisingly large portion of the time, you don’t. This may seem like a rather abstract idea, but I discovered the best way to find this out for yourself it to talk to your parents and siblings about your childhood. All those little memories, some big and important, some just flashbacks, like I remember being in a toy shop and picking out a puppet dog. But if you talk about them you’ll find that other people remember them differently. I’ve been surprised to discover that things I remember doing, my parents remember my brother doing instead, and some things they don’t even remember happening at al.

For a  more up-to-date version of this, try talking to your beloved about the history of your relationship. I know talking to my partner reveals some interesting diversions in the ‘facts’! It’s not that either of you are willingly lying, it’s just that you remember things differently, depending on how you felt about them then, and how you feel about them now. Next time you go to tell the same story, it may be different again. A great many things influence our memory, not least our emotions. Essentially, every time we access a memory, it is changed. It’s not a purely psychological discussion: of prisoners exonerated by DNA, 75% are mistakenly identified (while there is more behind this figure than just memory and emotion, eyewitness testimony in general is considered increasingly unreliable).

When it comes to health, several more things coalesce with emotion and memory to create a false impression of what’s going on. One is “regression to the mean,” which is a fancy way of saying we get better on our own. Our bodies have immune systems, and they do their work. Think about when you have a cold – everyone knows we can’t cure the common cold, and all the things we take are just to make the symptoms less annoying until our own body can work it out of our system. This works for much more than the common cold, our body’s immune systems has evolved to be pretty good at fighting off ailments of all sorts. I summarized some research the other day on ultramarathon runners, many of whom suffered painful inflammation of their upper leg tissue, but even after continuing to run, many of them simply got better.

Another is that we remember the wins far more often than the losses, especially when we really want the wins. If you want an alternative medicine to work, you’ll remember the times someone got better while using it far more often than when they didn’t. Another common issue with alternative medicines is care and attention. Yes, it is true that alternative practitioners will spend more time listening to your problem than traditional doctors, who simply do not have the time. Which is not their fault. Nor does it mean their medicine is less effective, and the alternative medicine more effective. It’s just that people’s mental state has a lot to do with how they respond to  treatment, and being given a sympathetic ear goes a long way towards that. I absolutely lament that mainstream medical doctors do not have the time to listen properly, but that’s a product of systems where we ensure everyone has at least some health care. Frankly, I’d rather it that way. But it does allow the alternatives space to appear heroic.

Of course, with this post I’m again talking about homeopathy. Some people swear it works, by their own experience or those of people they trust. But the only way to avoid our subjective biases, that is, to discount the effects of our emotions and hopes, is to conduct clinical studies. And study after study after meta-analysis shows homeopathy performs no better than a  placebo – that is, the belief that you are getting medicine giving a positive boost to your disease-fighting power.

So we’re faced with two very conflicting things. Our experience appears to tells us one thing; the evidence tells us the exact opposite. One of these must be wrong. Given all the fallibilities of memory, emotion and how our power to fight disease works; and given the stringent controls on drug trials that have provided us with a model of finding out what really works, I know which side I reject.

The investment of time and love in fighting disease also works on animals. If they feel the warmth of your arms and the weight of your care, they’re more likely to fight stronger. You don’t need the “holy water” (at a steep cost) to get the same result; just love them. And give medicines that are proven to work.


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