In our recent paper, we show that people usually underestimate the range of their hand movements. Is that an interesting finding? Absolutely! In our everyday lives, we constantly use our hands: we write, grab things, type on our computers, and perform a multitude of other actions. We are pretty proficient in those tasks, even if sometimes something goes wrong and we miss that ball we were trying to catch. Having so much experience suggests that we have a pretty good idea of how our bodies move, right? Well, our research indicates that might not be the case.

Before we launched this project, we discussed the whole idea among ourselves. Gilles was the first to ask the question: Are people accurate in how they think they can move? Heated discussions followed about why this would even matter. We then casually started asking our friends to judge how much they think they can rotate their hands in one direction or another. It turned out they were quite a bit off in their accuracy. In the initial discussions, we were thinking of measuring estimations of extreme movements, such as those performed by professional gymnasts and dancers. These are usually the kinds of movements that non-professionals look at thinking, “I could never do that.” But we found that even mundane hand movements could elicit this kind of reaction. Think about the flexion or extension movements we describe in our paper: Do you think your hand can reach a 90° angle? In our research group, one of us could bend it this much, which surprised the others. So, we decided to test that and run a pilot experiment.

When we started working on this, the world was still under lockdown, which led to these first pilot experiments being conducted online. It was not an ideal situation, and despite knowing we were onto something, we figured the online setting was pretty bad for measuring participants’ real movements accurately. We were disappointed, but we didn’t give up. After the lockdown mandates were lifted, we tried again in an in-person experiment where we could control the setting and accurately measure the hand movements. We did that at two different locations (Louvain and Coimbra) and using two different experimental tasks (experiments 1 and 2 of the paper). To our surprise, when comparing the data of the two experiments, the results were very similar in how much people underestimated their hand movements, and even the results of the online pilots weren’t that far off.

Our study is an example of research born from observing the world around us and then transforming our observations into an experiment. How often are you impressed by seeing a gymnast stretching their body far beyond how you think yours would stretch? Your brain probably has some capacity to estimate and imagine how flexible your body is. As we show, these estimations are rather conservative and aimed at preventing injury when stretching yourself too enthusiastically. That means our knowledge of our own body movements is not an accurate representation, but rather an approximate and fuzzy result of filtering our real movement limits through what is more useful in the real world.

This is especially important for sports and rehabilitation professionals: They might want to know these cognitive limitations to help us perform better and recover faster. So, next time you think you can’t touch your toes, remember: Your brain might just be playing it safe!