The culprit behind limited working memory capacity

What does a snapshot of human cognitive architecture show- a sensory system allowing us to take in a lot of information from the world, a vast long-term memory store and a severely limited working memory store. The limited working memory store represents a bottleneck in human cognitive processing. Two recent studies published in Nature show that the brain area related to the capacity limitation of memory capacity has finally been located!

This is a striking finding. We have known for a while that there are strong limitations to working memory. However it has been unclear how the limited capacity plays out in the brain. Well, its still not entirely clear how it plays out in the brain. But these two studies do mark a solid beginning towards that understanding.

The same basic result was was reported by two labs, using different methodologies. One lab used fMRI
(or functional Magnetic Resonance Imagine – watching pretty pictures of the brain in the magnet). The other one used Electrophysiology (using surface electrodes). Both studies implicate the posterior part of parietal cortex. (Note, there are many brain areas involved in working memory. Only one seems to be related to the capacity limitation, which is surprising).

Results also show significant individual differences in memory capacity and neural activity. Most people could hold three or four things in their minds at once when given a quick glimpse of an image or word. But some were able to hold only one or two items at a time.

What does this finding mean for HCI? This specific finding probably does not mean much. It is simply one more step in understanding the whole picture about working memory. But I do think that in the heated debate about the capacity of working memory implications for menu structures (1, 2,
3), HCI has ignored the larger picture about working memory.

Working memory plays a crucial role in complex cognition. Whether reading a newspaper, or calculating restaurant tip, or making a complex decision, one has
to temporarily store information in one’s mind during intermediate steps. Much of cognitive information processing can be understood as an interplay between a small working memory store and a large long-term memory. There are so many questions about this interplay. How does information get into working memory? How does it get out? What information gets transferred to the long-term memory store? Is there one working memory store or are there multiple stores (one for visual information, another for verbal information etc.). What is the relationship between working memory and attention? So many questions…

For the curious, here is a visual model of current thinking about working memory. Working memory has three components

  • A VisuoSpatial SketchPad that holds visual and spatial informaiton
  • A Phonological Loop for holding verbal information
  • A Central Executive that decides what information enters, stays and is let go from the VisuoSpatial SketchPad and Phonological Loop

The model also depicts the interactions of working memory with the sensory systems on the one side and with the long term memory store on the other side.

What do you think about working memory and its significance for Human Computer Interaction?

2 thoughts on “The culprit behind limited working memory capacity

  1. Working Memory – Bottleneck or Accelerator?

    I am a computer programmer and knowledge enthusiast and not a designer or scientist per se. However, I am fascinated by the entire notion of memory, perception, and cognition. When reading this article at the point it referred to working memory being a bottleneck, it immediately made me think of a race-car driver, who has to continually plan at the split-second level how to steer the car, both the survive and then to win – or a fighter, only to, also at the split-second rate, completely forget it, as full attention is forward only. Similarly a soldier – who neither needs to, nor can afford to “process” over time what is happening around him or her must act or react accordingly. Isn’t it interesting that most people regard those types of situations as a blur. There seems to be some connection not only about the capacity of working memory, but also to the rate at which it is consumed and reused. So, whether the memory is implicit or explicit I don’t know, but I see it as what allows an individual to “work”. Without it, we would be unable to function.

    I have thoroghly enjoyed reading the articles on this site.

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