I bought a plastic mat to put underneath my desk chair, to protect the wooden floor from having bits of stone ground into it by the chair wheels. But it kept sliding when I stepped onto it, nearly sending me stumbling into my large, expensive, and fragile monitor. I decided to replace the mat as soon as I found a better one.

Before I found a better one, though, I realized I wasn't sliding on it anymore. My footsteps had adjusted themselves to it.

This struck me as odd. I couldn't be sensing the new surface when stepping onto it and adjusting my step to it, because once I've set my foot down on it, it's too late; I've already leaned toward the foot in a way that would make it physically impossible to reduce my angular momentum, and the slipping seems instantaneous on contact. Nor was I consciously aware of the mat anymore. It's thin, transparent, and easy to overlook.

I could think of two possibilities: Either my brain had learned to walk differently in a small, precise area in front of my desk, or I noticed the mat subconsciously and adjusted my steps subconsciously. The latter possibility freaked me out a little, because it seems like the kind of thing my brain should tell me about. Adjusting my steps subconsciously I expect; noticing a new object or environment, I expect to be told about.

A few weeks later, the mat had gradually moved a foot or two out of position, so I moved it back. The next time I came back to my desk, hours later, having forgotten all about the mat, I immediately slipped on it.

So it seems my brain was not noticing the mat, but remembering its precise location. (It's possible this is instead some physical mechanism that makes the mat stick better to the floor over time, but I can't think how that would work.)

Have any of you had similar experiences?

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I wouldn't entirely rule out a physical mechanism. If you make a big motion (placing it initially or shifting it back into place) then it does not match the floor surface. But as you press down on it in different places over time, it is pressed in. If that makes it very slightly deform, then the contact area increases dramatically, increasing friction to a similar dramatic extent.

Maybe. Depends on the material.

(Note: the approximation that friction is independent of surface area assumes flatness. It does not apply if at least one of the surfaces is deforming to become more conformal)

This doesn't seem particularly odd to me. If someone moved the ignition of your car up by 20mm, I bet you'd slam your key into the surrounding plastic at least a couple times.

I can't think of many similar experiences.

but possibly things like; knowing the exact amount of force required to swing a door so that it shuts perfectly while making as little noise as possible. For each door in my house; all with different weights.

Cool story! But why did you expect that your subconscious would tell you when it learned something? Did your subconscious tell you when it learned the rule that specifies the precise ordering of words in the phrase "five smart Japanese government officials" (as opposed to for example "smart five government Japanese officials")?

I expected that if it was noticing the mat's presence, an object-recognition problem, that I would be consciously aware of it. I'm not aware that I subconsciously adjust to the presence of objects without realizing they're there.

I think that if we were made consciously aware of everything that our "muscle memory" has learned to do, that we would be inundated with information that would distract us from the executive overview of our lives. The micro-management of our existence would likely drive us insane.

The question here is whether this is a muscle-memory matter, or an object-recognition / reasoning one, and what the cue is, and whether the nature of the cue determines whether it enters consciousness. It suggests that "muscle memory" can be based on precise spatial location. Adjusting your step due to the presence of an object, however, is not muscle memory.

Reading the wikipedia article on "muscle memory", the concept looks like a dormitive principle. Taken literally, it makes no sense as applied to riding a bicycle (one of the examples in that article), because what you actually have to do with your muscles depends on what is happening with the bicycle in the moment. You are not playing back a stored recording of muscle movements.

Likewise walking on a slippery mat.

Based on my own experience, it seems like 'muscle memory' means your brain learning abstractions of motion. So when you know how to ride a bike, you only have to consciously think 'turn left' rather than 'move my right hand forward and pull my left hand back and lean a little bit to the left'. These abstractions are not just recordings, as they can vary along one or more dimensions: you can turn sharply left or gently left, and your 'muscle memory' knows how to implement that.

'Sit in my desk chair' might also be a learned abstraction that involves navigating the slippery mat.

you only have to consciously think 'turn left' rather than 'move my right hand forward and pull my left hand back and lean a little bit to the left'.

That isn't how you turn left on a bicycle, consciously or otherwise. If you do that you will fall off to the right. What you actually have to do is control your rate of falling over at close to zero while also controlling the rate of turning at a desired value. This cannot be done by memorising any mapping from desired turn rate to anything that you do with your muscles. A bicycle is an unstable system that the rider must continuously maintain his balance on.


While true, this misses the point of his post, which is that muscle memory is the unconscious mastery of a complex abstraction.

That brings it back to dormitive principles again. What would it mean for muscle memory to not be "the unconscious mastery of a complex abstraction"?


It would mean that SilentCal had not given you a useful keyword you can use to learn more about something that perplexed you.

You can think "turn left" and without any other conscious input your body executes a successful left turn on the bicycle. Something is happening in between; the common name for this something is 'muscle memory'. It's not necessarily a great name.

We don't know exactly how muscle memory works, but we can make observations about its functioning. For instance, that it cannot consist solely of exact repetition of motions, and that it must be able incorporate real-time sensory feedback (or else biking would be impossible).

Do we disagree on anything?

Do we disagree on anything?

Only the usefulness of the name. "Stuff" would more clearly capture what we know about it. :) I think we can leave it there.

nearly sending me stumbling into my large, expensive, and fragile monitor.

Basically you experienced a trauma. Physiology 101 suggests that if you get into the same location in which you experienced a trauma in the past you brain will react to the trauma and avoid the action that produced the trauma in the first place. That's a process of learning that I would expect to happen and most of those reactions are unconscious.

The latter possibility freaked me out a little, because it seems like the kind of thing my brain should tell me about.

"Did you leave your umbrella to the left of your shoes, or the right?"

"101 Zen Stories"

This seems to be almost the same as dealing with escalators - you have to adjust to the moving steps.