Science Interviews


Mon, 2nd Mar 2015

How do our memories work?

Dr Michelle Ellefson, University of Cambridge

Listen Now    Download as mp3 from the show Eureka! Experiments that Changed the World

Psychology is a relatively new science; it wasnít separated from philosophy until the 1870s, when people realised that it was possible to conduct experiments in psychology, just like in the other sciences. One of these early experiments was conducted by Herman Ebbinghaus, who wanted to test how String remindergood his own memory was. With the help of Ginny Smith, Michelle Ellefson tried out the kind of experiments he used on our audience...

Michelle - So, you're going to do a list of items. I'm going to name them off one by one. Just like Ebbinghaus's experiment where he actually learned these 3-letter words. They were nonsense words. He learned them himself and he measured how well he could do at remembering them later. So, weíre going to get everyone to participate. So first, you just have to try to remember as many of these as you can. Alright, 1- MQK, 2-PCH, 3-RLV, 4-JPF, 5-XDT, 6-VKM, 7-FTG, 8-QHN, 9-SNB, 10-LJC.

Ginny - Do you think you got them all? No? I'm seeing some quite pained looks around the room. People find that quite difficult? Yeah?

Michelle - Would you believe that he learned over 84,000 of these throughout his experiment? He studied them for over 800 hours.

Ginny - That's dedication.

Michelle - So, weíre going to see how many the audience might be able to remember. Do you remember what the first one was?

Ginny - Hands up if you think you can remember it. There's probably 10 here in a room of maybe 50.

Michelle - Shout it out if you think you know it.

Ginny - Okay, on the count of three Ė 1, 2, 3...

Audience - MQK.

Michelle - Good. How about the last one?

Ginny - Hands up if you remember it. Okay, weíve got 3.

Michelle - Itís a smaller number than the first one. So, what do you think the last one was?

Audience - JLC?

Michelle - Close. There's few mixed up letters, but LJC, that's pretty good. Okay, so what about number 6?

Ginny - Weíve got no hands up. So, why is it so much harder to remember the ones in the middle than the first one or even the last one?

Michelle - One of the reasons why the largest number of people in the room remembered the first one is because as I was going through the list, it was the first one that you were kind of rehearsing in your mind. So, you rehearsed it more times than any of the others. As you got to about the third or the fourth item, because these items don't really have meaning for us, then it just started to be a jumble. The last one, people remember was a little bit higher rates because itís the last one you've heard. So, what this experiment demonstrated was something that people called the serial position effect

Ginny - Why was this such a historically important experiment?

Michelle - The first one is that no one believed that we could measure higher order thinking, just our general thinking skills in an experiment. Everyone before this point had thought about thinking skills and cognition through thought experiments and philosophy. But nobody thought we could actually do an experiment to measure our thinking skills. The second reason why it was really important was that while Ebbinghaus was conducting this research, statistics were just coming on the scene. He in his seminal work took lots and lots of statistics. So, he unfortunately did all this work on himself which is a criticism, but he took averages. So, he have these lists of 10 items and heíd have an average of how long it took him to learn a list. And how easy it was to forget a list. If you want to go back and relearn it, how quickly he could relearn it. So, he had lots and lots of statistics and he used a lot of terms that psychologists hadnít really been using before to that extent.

Ginny - Is this something that we can use to help ourselves learn better to help children learn better?

Michelle - So, one of the things that Ebbinghaus did in his learning of these various lists, he engaged in what people now call distributed practice, which is doing a little bit often. What a lot of people who study cognition and learning now think is that that's one of the best ways to learn. So, we might think that itís a lot easier to learn a bunch of stuff if we block learn it, which means we focus on one thing until we know it. But actually, in terms of memory, we do a lot better if we can space out our practice and do a little bit every day.

Ginny - So, there's a real reason you shouldnít just cram for exams.

Michelle - Yeah, you wonít remember it.

Ginny - Now, did we want to see if anyone here has got a really good memory and can still remember any of those word lists?

Michelle - So, shall we start with one? Since you now know one is maybe the easiest, does anyone remember what the first item was?

Ginny - Weíve got a couple of, a few hands. I think itís less than the first time.

Michelle - Itís less than before. So, that's another one of Ebbinghaus's results from his finding is this idea that the longer you go from learning something, the more you forget. This later became called the forgetting curve. So, in relation to examinations, the reason why this thing called distributed practice works is because just as you're getting ready to forget something, you remind yourself what it is. So you might do really well in an examination if you cram for it the night before. But two days later, you wonít remember much.

Ginny - So, you need to do little and often and then cram as well- that's the worst of all worlds! So, who thinks they can still remember number one?

Audience - MQK.

Michelle - Very good, but I'm sure no one remembers number 7. You think you remember 7?

Audience - TMG?

Michelle - Close but not quite. Itís FTG.

Ginny - So, if people do remember a random one, is that likely to be because it means something to them? If it was say, your initials, you'd remember it.

Michelle - Yeah, so I tried to be really careful in creating these sets of letters to try not to have something that was meaningful. But that's another part of memory is that the more meaningful something is, the easier it is to remember.

Ginny - Fantastic advice. Iíll remember that next time I'm doing an exam although hopefully, that wonít be any time in the near future. That was Michelle Ellefson from Cambridge University.



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