As clinicians it has never been more important to be evidence based (informed), to audit our outcomes, and essentially do the best we can by our athletes. Yet what we are not taught during any of our years of training is just how flawed we all are as humans when it comes to the way we think and our (potentially detrimental) desire to search out patterns, formulate relationships between things and attribute causation. There are numerous ‘logical fallacies’ (errors in reasoning) we fall foul of which have significant implications for all healthcare, including Podiatric practice, and it is important to identify them and talk them out so we can do our best to try and not commit them daily, or at least be aware of when we may be doing so. This blog will address the fallacy known as ‘post hoc ergo propter hoc’, which is Latin for “after it, therefore because of it”.
“A CAUSED B, BECAUSE A WAS FOLLOWED BY B”
Our patients are just as guilty of committing this fallacy (often shortened to just ‘post hoc fallacy’) as we are, as we will come on to mention. However, this faulty reasoning is everywhere; the media, the movies, our friends and family. Looking for them in these places can be fun (but don’t be the person who continuously points them out; no-one likes that person). Let’s look at some examples:
- In an episode of the Big Bang theory the gang return from an expedition to the North Pole and Sheldon is on the phone to his mother. When he tells her he is home safe she tells him that is because her and her church group prayed for his safe return. He calls her out for committing a post hoc fallacy. (Could the same point be applicable to all praying? I’m not going to go there…)
- It is well documented that sportsmen and women often have ‘superstitions’. They often develop these from doing something once, performing really well, committing a post hoc fallacy by attributing correlation, and then continuing to do whatever that one (or more) thing/s were from then on. It is rumored John Terry wore the same pair of shin pads for 10 years and listened to the same CD before every match.
- The highly covered ‘Vaccines cause Autism’ debate (it’s not a debate; they don’t!) is a classic case of the post hoc ergo propter hoc fallacy; claiming one thing followed another without the evidence to support it.
So some post hoc fallacies would be really obvious. For example, if I noted that on completion of typing this blog it started raining, and then claimed that it rained because I typed this blog then you would be quite right to question it. So how does this apply to healthcare/Podiatry? Well, unfortunately the post hoc fallacies we (and our patients) are likely to commit are significantly less obvious.
This is important because factors surrounding our own confirmation bias (desire, expectation, self fulfilling prophecy etc.) will colour the way we practice. How many times have we seen clinicians performing practices with no evidence (or worse still, evidence to the contrary) say things like “it works for me” or “the results speak for themselves”? Worth remembering the old sayings: ‘The plural of anecdote is not data’, and my personal favourite which I find myself using almost weekly: ‘Science doesn’t care about your opinion’.
What about when we provide an intervention (anything from homeopathy through to joint mobilisations or orthoses) and then we, and/or our patients, attribute the outcome (good or bad) to that intervention? Is this always appropriate to do? Or are we getting tricked by the temporal sequence of events and committing a post hoc fallacy? For example, we may ‘diagnose’ a pelvic asymmetry in someone who presents in pain, and following our assessment and issue of a unilateral heel raise we review them and they report less pain. So we declare we must have been correct in our diagnosis, and our intervention was definitely the reason they had a reduction in pain. Simple, right? NOPE.
So what could be happening here? Is there another explanation for a change in symptoms following an intervention? Many, it turns out. The placebo effect of course (if the change was positive). Also things such as the natural history of a given condition, and regression to the mean. An article which I need to flag here as I think it should be must read for all and covers this in far greater depth is linked to HERE.
I’d recommend we all archive this and give it a read at least once a month to remind ourselves how flawed we (our brains) really are! Yet again, things are not as simple as they appear and we can’t ignore this just because it is inconvenient. We owe it to our athletes to be honest, transparent and human; and to be human is to be imperfect.
