In honor of @Foone's thread on the *visual* quirks of our brains, let's talk about "how bullshit insane our brains are": sensory and motor systems edition.https://twitter.com/Foone/status/1014267515696922624 …
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Just like with the visual system, "hack your time perception" is trick is one that our brains employ a whole lot, to try make actions *appear* as if they're happening at the same time. This probably makes cause-and-effect easier to associate.
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For example, try scratching your leg. You can feel your hand move; you can feel force in your fingers. You can feel your nail on your skin. Feels like they're all happening at about the same time, right? Wrong.
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Your motor commands zips down from your brain through α-motor neurons to your fingers at around 100 m/s. They move; your legs then feel that scratch slowly at 40 m/s through type II sensory fibers. That signal's roundtrip takes 40-50 ms to just travel through your body.
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After the sensory signals process, 100-200 ms has passed - from intent to conscious sensation. For reference, that would be the network roundtrip time from the US west coast, all the way to Europe, *and back*.
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Crazy thing is, if that happened in a game you're playing, you would complain about lag. But for scratching, you *don't feel it at all* - your brain hacked time perception backwards to make you think the movement intent, the movement, and the sensation occurred at the same time.
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This "hack sensations back in time" trick is also related to another effect - cancelling the sensations of your own actions. In movement neuroscience (and controls), this is the "efference copy". You expect the movement to feel a certain way, then you subtract that expectation.
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Subtracting the expected sensation from the actual one -- that is, paying attention to what *wasn't* unexpected -- is a great strategy for a lot of reasons, chief among them being that the brain doesn't have to waste as much energy paying attention when things are *going right*.
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Most people can't tickle themselves. Even using a tool, like a pen, it's very hard. Ever wondered why? One of the dominant reasons is that our movement efference copy is being canceled out, muting the feeling. But! That cancellation only works within about 150-200 milliseconds.
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In a famous experiment in 1999, Dan Wolpert's lab built a robot. You moved the robot's arm, and another arm mirrored your movements, after an adjustable short delay. You could now in fact tickle yourself - as long as the robot copying your movements was delayed by about 200 ms.pic.twitter.com/u5d9gQc19n
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I get the feeling there's a certain industry you could patent & sell this concept to and become a billionaire.
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Replying to @RichFelker
Let’s just say... that the prosthetics industry has long understood that comfortable coupling with skin with minimal effects is an extremely difficult problem. So that needs to be solved first.
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