Eggs, Milk, Butter, And . . . Darn It.

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New research confirms two things. First, I’m not the only one who keeps forgetting that fourth thing I need at the grocery store. And second, I probably won’t get better at remembering it. Translation for lawyers: if you need jurors to keep more than a handful of facts in working memory, you have to give them special tools.

“A certain number of objects” — and no more

“We found that every person has the capacity to hold a certain number of objects in his or her mind,” said Jeff Rouder of the University of Missouri. He’s the co-author with Nelson Cowan of “An assessment of fixed-capacity models of visual working memory,” published this month in the Proceedings of the National Academy of Sciences. (Note: that link is to the PNAS abstract. Rouder posts the whole article here (PDF) at his Missouri bio page, a generous move I hope more scholars follow, but it’s extremely heavy going. Unless you love statistics or have time on your hands, the excellent press release is where you want to be.)

It wasn’t easy for Rouder and Cowan to confirm our “fixed capacity,” because we’ve developed clever tricks like “chunking” to get the most out of limited memory space:
Rouder said that to remember a series of items, people will use “chunking,” or grouping, to put together different items. It can be difficult for someone to remember nine random letters. But if that same person is asked to remember nine letters organized in acronyms, IBM-CIA-FBI, for example, the person only has to use three slots in working memory.

Nine slots, or three?

Our habit of “chunking” information into our memory slots makes it hard for researchers to understand how working memory really works. Until Rouder and Cowan devised an experiment that “wiped out” prior information as the subject went along, no one could tell whether subjects who remembered nine facts had kept each one in a different memory slot, or chunked them into, say, three groups of three.

It doesn’t matter to the subjects, of course, how many memory slots they have, as long as they end up remembering nine facts. But it matters a lot to lawyers. If you need jurors to remember nine facts, Rouder and Cowan’s research suggests, you’ve got three or four slots to put them in. If you can’t form the facts into meaningful groups, they won’t stick.

Remembering to pay attention

In fact, if you can’t sort facts into related groups (or give jurors some other tool to remember them, like notetaking) jurors may end up not listening to you at all. The press release goes on:

Working memory is closely related to attention because it requires attention to hold a number of items in mind at once. People with high working memory capacity have more focus. Those with a lower attention span are more easily distracted.

Next time jurors start staring at the ceiling during your client’s testimony, don’t get mad; think back. Where did you lose them? Likely somewhere around the fifth fact.