Skip to main content

procedural memory

More about motor memory

I don’t often talk about motor or skill memory — that is, the memory we use when we type or drive a car or play the piano. It’s one of the more mysterious domains of memory. We all know, of course, that this is a particularly durable kind of memory. It’s like riding a bicycle, we say — meaning that it’s something we’re not likely to have forgotten, something that will come back to us very readily, even if it’s been a very long time since we last used the skill.

For several decades there’s been argument over where motor memory is created. Now at last the dispute has apparently been settled, in favor of both contenders. What we needed to clarify the evidence was to realize that short-term motor memory is a quite different animal from long-term motor memory, and the two are created in different places.

The differences between short- and long-term motor memory have important implications, so let’s take a look at them.

First of all, it appears that short-term motor memory is created in the Purkinje cells of the cerebellar cortex, while long-term motor memory is transferred to the vestibular nucleus (axons from the Purkinje cells extend from the cerebellum to the vestibular nucleus in the medulla oblongata.

A similar process occurs of course in other types of memory. Most memory (for experiences, for information) is created in the hippocampus, and later passed on to regions in the cerebral cortex for long-term storage. However, that process of consolidation and transfer takes weeks. Motor memory moves from short-term to long-term much more quickly — within as little as a few hours, in some cases, or a few days at most.

There’s another important way in which motor memory differs from ‘ordinary’ memory. Again, it’s not qualitatively different, but an extension of the normal process. We don’t usually remember everything. Long-term memory is more a memory of gist than precision. Details are lost; what we remember for the most part are the broad strokes on the canvas. Similarly (though rather more markedly perhaps), short-term motor memory is quickly lost, passing on only the rough shape of the process to long-term memory.

For example, in the mouse experiments that demonstrated all this, the mice were taught to follow the movement of an object by moving their eyes in a particular way. With practice they got better at this particular eye movement, and if they practiced the task on a daily basis for several days, they were able to maintain this skill. It had been established in long-term memory.

However, this is a simple skill. When monkeys were taught a more complex skill — to follow a moving ball as its speed increases for a fifth to a tenth of a second — although they usually mastered the task quite quickly, it was also forgotten just as quickly. The researchers say such “sophisticated” motor memory is easily lost in just ten to 15 minutes.

A more human example is how a baseball batter can learn to hit a curve ball after the movement of the ball has been observed several times and memorized. It’s an advantage to pick this information up quickly, but the price seems to be that it is also forgotten quickly.

Riding a bicycle is the archetypal example of the durability of motor memory, but there’s also always a caveat: with just a little practice, we say, you’ll pick it up again. But you need that practice, and to get as skilled as you were in your heyday, you need more practice. Motor memory may be durable, but it’s only the broad outlines of the procedure that are ‘locked in’.

Of course, what constitutes the ‘broad outlines’ is clearly something that must change with practice. A concert pianist who’s been in retirement for five years and someone who learned the piano as a child are not starting off on the same foot! The ‘broad outlines’ the concert pianist has salted away must be considerably more sophisticated than those of the childhood pianist. It would be interesting to see the differences between experts and novices explored.

But in the meantime, there are two useful lessons we can take from these studies. The first is the need to brush up your skills before expecting them to be at their best (the researchers suggest that even professional musicians, accustomed to playing every day, need to ‘remind’ themselves of their skill before a concert). The second is one connected to the speed with which short-term motor memory transfers to long-term memory.

The researchers found that the animals learned more quickly when their training was broken into shorter intervals with breaks — for example, dividing an hour-long training session into four 15-minute exercises with intervals of 30 minutes between them. For this to be true, however, the cerebellar cortex needed to be active. This implies that something happens in this part of the brain during periods of inactivity that’s important for creating long-term memory. I’m reminded here of other recent research pointing to the importance of “quiet time” for consolidating new learning.

None of this contradicts what we already know about how to learn and practice a skill, but it does add to our understanding and reinforces the idea that it’s better to practice a skill regularly in small bites, rather than in lengthy sessions (I’m not denouncing the long sessions a musician, say, puts in on a daily basis. But the recommendation would be not to practice one specific thing for too long at one go — better to move on to something else, and, repeatedly, come back to it.)

For more about how to practice, check out Learning a new skill, Spacing your learning and Acquiring expertise through deliberate practice

 

Forgetting a skill or procedure

  • Memory for skills — procedural memory — is stored as action sequences, in our unconscious memory.
  • Because this type of memory is very reliable, failures are usually particularly puzzling and even distressing.
  • Because the memory is less accessible, we also tend to have problems dealing with failures.
  • Failures occur when an action sequence becomes disrupted for some reason. When this happens, we have to retrieve the knowledge stored in our conscious memory, that we used when learning the skill.

Have you ever been driving a car and suddenly you’re not sure what to do? You’re traveling along in usual automatic fashion and there comes a moment when you need to engage a new subroutine — say, you need to give way at an intersection, or you stall at the traffic lights, or you stop the car — and suddenly, you don’t know what to do. There’s a flash of panic, even while you’re thinking, “This is stupid, I’ve done this a thousand times”, and then, maybe it’s all right, maybe you have to take a moment to get your head in the right space, and ... okay, you’re off again, control safely in the hands of the automatic pilot.

But you’re unsettled. There are lots of ways our memory fails us. Some of these are very common, so common we just accept them — noone (well, few of us) expect our memories to be 100% perfect all the time. But procedural memory — the memory that allows us to drive a car, ride a bike, type, play the piano, etc — is different from other types of memory. We don’t say “it’s like riding a bicycle” without reason. Once we’ve truly mastered a skill, we expect to have that, for ever. And, for the most part, we do.

The thing about procedural memory — the big difference between it and so-called declarative memory — is that it is not in conscious memory. That’s its huge advantage; we could never perform skills fast enough if they were under conscious control. As we acquire a skill, the declarative information we learn (‘use your little finger on the “a”; the “s” is next to the “a”; the “d” is next to the “s” ’ etc) is transformed into so-called “procedural rules”, which are completely internalized, beyond our conscious manipulation. This greatly reduces the involvement of working memory, and protects the skill from the types of interference that other types of memory are vulnerable to.

It also means that when we do have a failure, we really don’t know how to deal with it. A conscious mental search is not going to retrieve the needed information, because the information we want is not in our accessible database. So what usually happens is that we are forced to default to our backup — the declarative information we encoded during the original learning process. It is this that accounts for the lack of fluency in the subsequent actions; to regain fluency, you must engage the unconscious action sequence.

I don’t know of any research that has looked into these occasional glitches, but I presume that what happens is that the action sequence doesn’t immediately engage. As soon as it doesn’t, we pay attention — that makes it even more likely that the action sequence won’t be triggered, because conscious awareness is precisely what we don’t want.

One piece of research that is relevant to this is a recent study that looked at the phenomenon of “choking” — top athletes performing below par at crucial moments. It’s suggested that the problem lies in part in the athlete paying too much attention to what they’re doing. Skills are the one area of memory where too much attention is deleterious to performance!

I think the best way to deal with this very occasional glitch in performance is to relax, stop thinking about what you’re doing, go back a little in the action sequence to an obvious starting point (if you can’t or don’t need to physically re-do earlier steps, mimic the steps). Remember that skills are stored as sequences, and it’s hard to break in halfway through a sequence, you need to start at the beginning.

You can read more about skill memory and about the best way to practice.

You might also be interested in a related (but separate) issue, that of action slips, which are a product of a lack of attention, not a surfeit.

This article originally appeared in the November 2004 newsletter.

Multitasking

  • Doing more than one task at a time requires us to switch our attention rapidly between the tasks.
  • This is easier if the tasks don't need much attention.
  • Although we think we're saving time, time is lost when switching between tasks; these time costs increase for complex or unfamiliar tasks.
  • Both alcohol and aging affect our ability to switch attention rapidly.

A very common situation today, which is probably responsible for a great deal of modern anxiety about failing memory, is that where we're required to “multitask”, that trendy modern word for trying to do more than one thing at a time. It is a situation for which both the normal consequences of aging and low working memory capacity has serious implications.

There’s an old insult along the lines of “he can’t walk and chew gum”. The insult is a tacit acknowledgment that doing two things at the same time can put a strain on mental resources, and also recognizes (this is the insult part!) that well-practiced activities do not place as much demand on our cognitive resources. We can, indeed, do more than one task at a time, as long as only one of the tasks requires our attention. It is attention that can’t be split.

You may feel that you can, in fact, do two tasks requiring attention simultaneously. For example, talking on a cellphone and driving!

Not true.

What you are in fact doing, is switching your attention rapidly between the two tasks, and you are doing it at some cost.

How big a cost depends on a number of factors. If you are driving a familiar route, with no unexpected events (such as the car in front of you braking hard, or a dog running out on the road), you may not notice the deterioration in your performance. It also helps if the conversation you are having is routine, with little emotional engagement. But if the conversation is stressful, or provokes strong emotion, or requires you to think … well, any of these factors will impact on your ability to drive.

The ability to switch attention between tasks is regulated by a function called prefrontal cortex. This region of the brain appears to be particularly affected by aging, and also by alcohol. Thus, talking on a cellphone while driving drunk is a recipe for disaster! Nor do you have to actually be under the influence to be affected in this way by alcohol; impaired executive control is characteristic of alcoholics.

More commonly, we get older, and as we get older we become less able to switch attention fast.

The ability to switch attention is also related to working memory capacity.

But multitasking is not only a problem for older adults, or those with a low working memory capacity. A study [1] using young adults found that for all types of tasks, time was lost when switching between tasks, and time costs increased with the complexity of the tasks, so it took significantly longer to switch between more complex tasks. Time costs also were greater when subjects switched to tasks that were relatively unfamiliar.

Part of the problem in switching attention is that we have to change “rules”. Rule activation takes significant amounts of time, several tenths of a second — which may not sound much, but can mean the difference between life and death in some situations (such as driving a car), and which even in less dramatic circumstances, adds appreciably to the time it takes to do tasks, if you are switching back and forth repeatedly.

To take an example close to home, people required to write a report while repeatedly checking their email took half again as long to finish the report compared to those who didn't switch between tasks!

In other words, while multitasking may seem more efficient, it may not actually BE more efficient. It may in fact take more time in the end, and the tasks may of course be performed more poorly. And then there is the stress; switching between tasks places demands on your mental resources, and that is stressful. (And not only are we poorer at such task-switching as we age, we also tend to be less able to handle stress).

There is another aspect to multitasking that deserves mention. It has been speculated that rapid switching between tasks may impede long-term memory encoding. I don’t know of any research on this, but it is certainly plausible.

So, what can we do about it?

Well, the main thing is to be aware of the problems. Accept that multitasking is not a particularly desirably situation; that it costs you time and quality of performance; that your ability to multitask will be impeded by fatigue, alcohol, stress, emotion, distraction (e.g., don’t add to your problems by having music on as well); that your ability will also be impaired by age. Understand that multitasking involves switching attention between tasks, not simultaneous performance; and that it will therefore be successful to the extent that the tasks are familiar and well-practised.

This article originally appeared in the February 2005 newsletter.

Planning to Remember

References

Rubinstein, J.S., Meyer, D.E. & Evans, J.E. 2001. Executive Control of Cognitive Processes in Task Switching. Journal of Experimental Psychology - Human Perception and Performance, 27 (4), 763-797.

Learning a new skill

To master a skill:

  • Practice it until you reach the stage where actions follow automatically
  • Practice more efficiently, by:
    • varying your actions
    • providing immediate feedback
    • spacing out your practice

Remembering a skill is entirely different from remembering other kinds of knowledge. It’s the difference between knowing how and knowing that.

Practice, practice, practice

Practice is the key to mastering a skill. One of the critical aspects is assuredly the fact that, with practice, the demands on your attention get smaller and smaller. Interestingly (and probably against common sense), there appears to be no mental limit to the improvement you gain from practice. Your physical condition limits how much improvement you can make to a practical skill (although, in practice, few people probably ever approach these limits), but a cognitive skill will continue to improve as long as you keep practicing. One long-ago researcher had two people perform 10,000 mental addition problems, and they kept on increasing their speed to the end.

How to get the most out of your practice

While practice is the key, there are some actions we can take to ensure we get the most value out of our practice:

  • Learn from specific examples rather than abstract rules
  • Provide feedback while the action is active in memory (i.e., immediately). Try again while the feedback is active in memory.
  • Practice a skill with subtle variations (such as varying the force of your pitch, or the distance you are throwing) rather than trying to repeat your action exactly.
  • Space your practice (maths textbooks, for example, tend to put similar exercises together, but in fact they would be better spaced out).
  • Allow for interference with similar skills: if a new skill contains steps that are antagonistic to steps contained in an already mastered skill, that new skill will be much harder to learn (e.g., when I changed keyboards, the buttons for page up, page down, insert, etc, had been put in a different order — the conflict between the old habit and the new pattern made learning the new pattern harder than it would have been if I had never had a keyboard before). The existing skill may also be badly affected.
  • If a skill can be broken down into independent sub-skills, break it down into its components and learn them separately, but if components are dependent, learn the skill as a whole (e.g., computer programming can be broken into independent sub-skills, but learning to play the piano is best learned as a whole).

How to Revise and Practice

References
  1. Anderson, J.R., Fincham, J.M. & Douglass, S. 1997. The role of examples and rules in the acquisition of a cognitive skill. Journal of Experimental Psychology: Learning, Memory and Cognition, 23, 932-945.
  2. Chase, W.G. & Ericsson, K.A. 1981. Skilled memory. In J.R. Anderson (ed.) Cognitive skills and their acquisition. Hillsdale, NJ: Erlbaum.
  3. Wulf, G. & Schmidt, R.A. 1997. Variability of practice and implicit motor learning. Journal of Experimental Psychology: Learning, Memory and Cognition, 23, 987-1006.