James Wu

@analogist_net

Engineer, neuroscientist, pessimist. I care about infrastructure. Making tech work with us, with our bodies, and with our societies before we die.

Seattle, WA, USA
যোগদান করেছেন মে ২০১৪

টুইট

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  1. পিন করা টুইট
    ৪ জুলাই

    In honor of 's thread on the *visual* quirks of our brains, let's talk about "how bullshit insane our brains are": sensory and motor systems edition.

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  2. ৬ জুলাই

    If people like and sound the alarm, please listen. These are people who have worked with building or maintaining systems you and I can’t see, but rely on every day. They can tell when things are breaking down.

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  3. পুনঃ টুইট করেছেন
    ৫ জুলাই
    -কে উত্তর দিচ্ছেন

    My favourite example - give someone a task with a standard computer mouse, but slowly add latency to the screen cursor. Do it slow enough and you can add seconds of latency and they won't notice. But suddenly remove that latency and they think the cursor is "reading their mind"!

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  4. ৪ জুলাই

    A lot of this is from how the brain weighs (heh) prior experience. A lot of work has been done in trying to figure out how experience is used - but the short story is that through extensive training you can be tricked into thinking the reverse too, that smaller feels heavier.

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  5. ৪ জুলাই

    Other bullshit insane effects include: - Lighter color feels lighter - More metallic feels lighter - Colder feels heavier

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  6. ৪ জুলাই

    Remember, the two objects weigh the same. And you can lift them the same way - by a handle on a string, say - and the bigger looking one still FEELS lighter.

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  7. ৪ জুলাই

    Another way your brain tries to blend vision and feel together is the size-weight and material-weight illusions. Basically, if a larger object weighs the same as a smaller object, the larger (less dense) object also *feels lighter*. As long as you get to look at it first.

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  8. ৪ জুলাই

    (Aside: while your 2-point acuity is ~1 mm, you can feel down to *nanometers* -- if you're allowed to stroke the texture. This is *awesome insane*, not *bullshit insane*. Basically, your brain turns the texture into a symphony of vibrating frequencies. )

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  9. ৪ জুলাই

    (A lot of this background -- and a lot of the ongoing work in neural touch perception at the -- I learn from my colleagues and . Look for work from them.)

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  10. ৪ জুলাই

    What is probably most bullshit is that tactile resolution is improved by whether or not you're *looking toward* the general direction of the touch. EVEN IF YOU CAN'T SEE ANYTHING BECAUSE YOUR ARM IS IN COMPLETE DARKNESS.

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  11. ৪ জুলাই

    What is less well known is that this is affected by whether or not those pins touch simultaneously, or one after another. It's also affected by whether or not the pins cause pain. It's even affected by whether you have chronic pain.

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  12. ৪ জুলাই

    A classic example of "tactile acuity" is 2-point discrimination, whether you can tell that 2 pinpricks are, in fact, from 2 different pins. Well, you might know that this is about a millimeter of acuity in your fingertip, and many centimeters on your torso. That's not bullshit.

    2-point discrimination: ranges from very fine on fingertip, to very course on torso and calf.
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  13. ৪ জুলাই

    Just as pointed that the visual system isn't like a camera streaming high-res video back at you, but is full of inconsistencies like blind spots and and selectively high-res (foveal) regions, the same thing is true of the skin on your body.

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  14. ৪ জুলাই

    And if you're curious, our lab was looking into if this illusion works if you're stimulating the brain directly as well, by passing currents into the sensory cortex in patients with implanted electrodes. (Yes, it does.)

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  15. ৪ জুলাই

    It shouldn't be surprising to you know that this illusion starts fading if the two touches become separated by more than 200-300ms.

    Rubber hand illusion feedback delay: 200ms and the sensation disappears.
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  16. ৪ জুলাই

    The word generally used is "ownership". It feels like it is part of you, because the sight of the touch, and the feel of the (separate) touch, are associated in your brain. If someone threatens the rubber hand with a knife, you flinch.

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  17. ৪ জুলাই

    If your hand is hidden well enough, and the rubber hand is placed in a plausible position, and the two touches are at around the same time, many people start to feel like the rubber hand is part of their own body.

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  18. ৪ জুলাই

    So the brain tries its hardest to try to mix all of these senses together into what it thinks is the same event. One of the more famous illusions is the rubber hand illusion. Stare at a realistic rubber hand, and have someone touch IT - and your own hand - at the same time.

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  19. ৪ জুলাই

    This cause-and-effect hack works in other ways too. One of the ways it does so is in sensory integration. As we now know, if you see, hear, and feel what you think is same event, these signals are probably all hitting your brain at *very* different times.

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  20. ৪ জুলাই

    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.

    Tickling sensations using a robot that copied your movements is about the same as if someone else tickled you, after a 200ms delay.
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  21. ৪ জুলাই

    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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