This paper seems to be one of, like, a dozen mostly equivalent review pieces on working memory that Baddeley has written over the years. This one strikes a nice balance between concision and context, so it’s the one I chose to read with care.
Baddeley’s contribution is the idea that working memory consists of multiple independent components. When he was writing this paper, there were only three parts that he’d identified in short-term, working memory: a place for remembering sounds, a place for remembering space and visuals, and a “central executive” who is in charge of the whole system. This is contrast to earlier models that didn’t feel the need to distinguish between different components of working memory.
There are two lenses through which I’m reading this. First, how did we get here? Second, what metaphors do we use to describe memory?
Here is a handy table from a psych textbook, by the way:
Where did Baddeley come from?
Baddeley positions his work as a reaction to the “modal model” of memory, popular in the 1960s, one that is represented by (I’ve learned) Atkinson and Shiffrin.
Atkinson and Shiffrin were people; this is all I know about them.
The modal model, according to Baddeley, looked like this:
- Short-term memory is one unit — no components. This is the working memory, the memory whose main function is to facilitate learning, reasoning, decision-making, etc.
- Long-term memory is where you keep memories for the long-term
- Here’s how long-term memories are formed: stuff automatically goes from short-term memory to long-term memory, but the process takes some time. (That’s why you don’t learn everything.) If you want to learn something, you have to make sure it’s rattling around short-term memory for long enough.
And what did things look like in the 1960s, when the modal model was prominent? I don’t have a clear picture of this. Wikipedia sends me to a piece from 1963 that talks of an explosion of results relating to short-term memory in the preceding years:
In 1958, and increasingly thereafter, the principal journals of human learning and performance have been flooded with experimental investigations of human short-term memory. This work has been characterized by strong theoretical interest, and sometimes strong statements, about the nature of memory, the characteristics of the memory trace, and the relations between short-term memory and the memory that results from multiple repetitions. The contrast with the preceding thirty years is striking. During those years most research on short-term memory was concerned with the memory span as a capacity variable, and no more…I venture to say that Broadbendt’s Perception and Communication (1958), with its emphasis on short-term memory as a major factor in human information-processing performance, played a key role in this development.
So the picture you get is that there was controversy about the distinction between short-term and long-term memory, springing from a great deal of results in the early ’60s.
One of the major impetuses? The famous psychological subject H.M. (Read about the controversies surrounding him in a fascinating New York Times magazine piece from a few years ago.) H.M makes an appearance in the Baddeley paper — he seemed to have the ability to form immediate memories (despite his profound inability to form long-term ones) help make the case for a distinction between short- and long-term memory systems.
And what was the state of things before the early ’60s? Baddeley credits Francis Galton with an early version (1883) of the notion that there are two separate memory systems, but I can’t figure out where exactly he says this or how he puts it. Wikipedia points us to William James, who distinguishes between primary and secondary memory. in the “Memory” chapter of The Principles of Psychology. I’ve only skimmed it, but I think he thinks of primary memory as a lot like the after-image of some visual perception. It just lingers for a second — real memory is secondary memory.
And what about before James and Galton? I’d have to figure that something as basic as the distinction between short- and long-term memory is not an insight unique to psychologists. I know a few other philosophers who make distinctions that seem relevant, but I’m not sure how to trace the lineage of short- and long-term memory before the late 1800s.
As it is, it seems that the early impetus is just the recognition that some stuff we can remember for a little bit, and other stuff we remember for a long time. Maybe this is as far as we get without more careful measurements.
Back to Baddeley, who makes the case that the modal model of the early 1960s is wrong. There are multiple components to short-term, working memory.
What was wrong with the modal model?
- Even when short-term memory is impaired, long-term memories can be formed just fine. So how could it be that the path to long-term passes through a unified short-term store? There has to be a pathway besides the damaged one that memories could pass-through, on their way to the land of long-term.
- This is hilarious, but the BBC tried to use the modal model in their advertising to let people know about newer wavelength bands they’d be switching broadcasts to. They figured the more frequently a phrase is in short-term memory, the more likely it is for a long-term memory to be formed, so they just slipped the phrase into radio broadcasts here and there and…nobody remembered. So much for “saturation advertising.” So how are
- The third thing — that people remember recent stuff better, even in long-term memory — is confusing to me. I don’t get how it’s relevant to this yet.
So what does he suggest, to fix things?
First, that there is a central executive that is in charge of making decisions during activities that is unrelated to the memory stores. I think this is supposed to explain how people who have short-term memory impairment can still function or form long-term memories. The assumption is that as long as the central executive (who decides what the brain should do) decides to actively reinforce the stuff that makes it into short-term memory, long-term memory can happen. And the central executive can also be in charge of doing stuff accurately, even if the stores of memory traces are depleted.
The central executive is a bizarre notion. Metaphorically, it’s a little dude in your head that decides where to put attention, or when to actively reinforce the memory traces in the other stories of working memory — thus he’s also responsible for learning and reasoning. He is, to put it bluntly, your soul, an unanalyzable source of free will. It’s weird.
Second, Baddeley proposes two different passive stores of memories — the phonological and the visual/spacial. Each comes with an active element, something that can reinforce the memory traces.
The metaphors are fascinating here. The phonological loop is, metaphorically, a piece of audio tape that loops around your brain, over and over. When a sound goes into your mind it lands on the memory trace, and then an active recording element has to rewrite the sound on your mental tape for it to be sustained over time. Otherwise, it gets overwritten (or it fades?) as time goes on.
Baddeley’s model for visual/spacial stuff could have used an audio tape metaphor, as far as I can tell, but chose something that felt more appropriate for visual information — a scratchpad. So there’s an entirely parallel system that is posited for visual info, but with a totally different set of metaphors that is appropriate for visual stuff.
So there’s a scratchpad, and when visual or spacial stuff comes into your head it is inscribed onto the pad, very lightly. It’s only sustained if the active element reinscribes it on the pad.
Let’s end here, because I’m still massively confused as to how any of the results that Baddeley says are issues with the modal model are satisfied by creating two independent stores of working memory. I’ll need to read something else to make any progress on this, I think.
Though, if you know more about this, please let me know! Open invitation to educate me about what’s going on here.
Update: I’m going to read this next.