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Neural physics
Has your foot ever heroically broken the fall of something slipping from your hands? Ever saved your nose by instinctively dodging an oddly bouncing basketball? Then it won’t come as a surprise that our brain has a remarkable grasp of the dynamic world around us. Often, it’s only after the fact, that you realise how complex an action was—yet your body pulled it off almost by itself. Many sports and games rely on this kind of intelligence too, like basketball or Jenga®. Strangely enough, physicists don’t necessarily excel at these, even though they can predict everything down to the last detail. So how is it that the brain effortlessly acts in accordance with complex physical laws, yet struggles when it comes to your physics exam?
Intuitive engineer
Our built-in understanding of the physical principles that govern the world is called physical intuition. It’s evolutionarily advantageous to have, since without it, you’d quickly run into trouble – think coffee spills, stolen bikes, or collisions with vehicles. Because this embedded knowledge is so deeply woven into our everyday actions, we rarely notice it. That makes it all the more surprising when our predictions turn out to be wrong, like that carton of milk you were sure was fuller than it actually is. Subtler prediction errors feel more like a perceptual tingle: you sense that something’s off but can’t quite put your finger on it. Take, for example, the confusing moment when a train next to yours starts moving, yet it appears as if you’re the one pulling away.
Prediction models
Interestingly, we continue to make many of these prediction errors consistently, even though we know very well what underlies our faulty perception. This has to do with the origin of our intuition for physics. Our brain doesn’t develop this skill out of fascination, but rather to function successfully in a complex world. As a major energy consumer, the brain aims for maximum success with minimal computational costs. To achieve this, it models the world based on patterns in sensory information, focusing on aspects that are relevant to our survival. That’s why strange quantum particles, magnetic fields, or radioactive rays don’t contradict our intuition.
What’s in our modelling kit?
That our brain is an avid model builder is clear. What kind of models it builds is still a topic of debate in cognitive science. The boundaries of our intuition provide a useful guide in this respect. By studying them, we know that our brain builds models of:
- Object trajectories: Where does that ball roll to? When do you step into a revolving door?
- Gravity/balance: Will that pile of dishes fall? On whose bike rack are you safe?
- Collisions and bouncing: How do you hit that squash ball? Where do you aim that billiard ball?
- Causality: Are this shuddering tree and that suddenly stopped car related?
- Material properties: On which surface do you have to ride your bike more carefully? Would I lie comfortably on those shards of glass?
- Object permanence: Does the same golf ball roll out of the tunnel in which the previous one disappeared?
We intuitively find it harder to predict multiple object trajectories at once, how strong a knot is, the movement of liquids, and forces involved in rotation. Different scientists explain these abilities or limitations in different ways. Some suggest that we rely on useful, self-devised rules of thumb, like heavy things move slowly, and movement doesn’t just stop. Others believe we do use physical laws, but simpler, quickly applicable versions of them. The most popular theory proposes an “intuitive physics engine,” with which we simulate bits of the world as a basis for precise predictions. Where do you think your brain gets its intuitive sense of physics from?
Credits
Author: Wieger Scheurer
Buddy: Lucas Geelen
Editor: Natalie Nielsen
Translation: Charlotte Sachs
Editor translation: Elena Markantonakis
Picture from cottonbro studio via pexels.com
