We’ve run out of milk and bread, so I’m going down to the supermarket to grab some. “We also need onions, and get some fish for dinner. Maybe some cereal and bananas for the boy,” comes a shout from the lounge. And I need some star anise, too. I’m sure I can remember that.
This will be familiar to you all. A list sufficiently short that we tell ourselves we don’t need to write it down, and research backs up our belief.
In a 1955 address to the US Eastern Psychological Association, American cognitive psychology researcher George Miller opined that he had, for seven years, “been persecuted by an integer”. This whole number stalked him across his research and the data he routinely collected, and peeked out from the scholarly journals he read. Though it didn’t always take exactly the same guise, it never changed, “so much as to be unrecognisable”.
The title of the address was “The magical number seven, plus or minus two: Some limits on our capacity for processing information”, so you can probably guess what that integer was.
At the time, Miller’s research had focused on experiments of absolute judgment, or what he reframed as experiments on the capacity to transmit information. For example, listen to up to 10 musical tones and, based on their relative pitch, tell me which of a pre-arranged list of answers applies. In these experiments, Miller found that people were pretty much spot on up to about five or six tones, but were poorer as the number of tones increased – seven seemed to be about the sweet spot.
In his address, he went on to note that the same pattern was appearing in other tasks, such as remembering a shopping list. The working span of our memory, the bit we can hold in our mind at any one moment, is about seven, plus or minus two – some folks struggle with more than five shopping items, and some folks can deal with nine.
In practice, this means that when the list gets past seven, you should probably either start writing things down or use a memory trick to remember them (cereal is dry without milk, star anise and fish make a starfish, onions and fish can smell if you leave them out, etc). Basically, you need to do something to transfer what’s in your working memory into long-term memory, because as soon as another item comes along it’s going to shunt something off the list (“Oh, and get petrol on the way back”).
But you’ll also have experienced another common phenomenon in this situation – the serial (cereal?) position effect. Seventy-one years before Miller took to the stage, Hermann Ebbinghaus reported a set of experiments he’d conducted largely on himself. He noted, among other things, that it’s easier to recall the first and last items on a list than those in the middle – I’m more likely to forget onions than either milk or petrol.
These are primacy and recency effects – things presented first and things presented last. Again, if you don’t do anything with the list, not only will items start to drop off, but it’s the most recent items that are most likely to drop off. The early list items are more likely to bleed into long-term memory.
I’m thinking about this work because we’ve just had a study break and the first major tests in our courses. To both show off the joy of cognitive psychology and give students evidence-based study tips, I’ve been teaching them about Miller and even more Ebbinghaus (the “forgetting curve”), Henry Roediger III (testing yourself on material aids retention more than just studying that material), and Alan Baddeley (navy divers remember more words if they learnt them under water than if they learnt them on land).
I could do the same here, and in fact I’ve started, but you might just want to write that list down, instead.
