100 Things You Should Know About People: #55 – During Sleep You Consolidate Learnings and Memories

Father and baby sleeping
You Sleep To Learn And Remember

Why do people sleep? — Well, not just people, but all kinds of animals sleep. When you think about it, it’s actually quite a strange idea that for 1/4 to 1/3 of each day we go unconscious and are oblivious to the world around us. Scientists for years have wondered and studied what goes on when we sleep and why we do it.

Some of the best research happens through serendipity — Matthew Wilson was studying brain activity in rats as they run mazes. One day he accidently left the rats hooked up to the equipment he used to record their brain activity. The rats eventually fell asleep, and to Wilson’s surprise, he found that the brain activity while they were asleep was almost the same as the brain activity when the rats were running the maze.

Learning and consolidating — Wilson started a series of experiments to study this more. And through his experiments he has come up with a theory, not just about rats, but about people too: When you sleep and when you dream you are reworking, or consolidating, your experiences from the day. Specifically you are consolidating new memories and making new associations from the information you processed during the day. Your brain is deciding what to remember and what to let go of, or forget.

Sleep don’t cram — Of course we’ve always heard the advice to “get a good night’s sleep” before a big event, or exam. It turns out that that advice was solid. If you want to remember what you have learned the best thing to do is to go to sleep after you learn and before you need to remember it.

And if you like to read research:

Ji D, Wilson MA (2007). “Coordinated memory replay in the visual cortex and hippocampus during sleep.” Nature Neuroscience 10: 100-7.

100 Things You Should Know About People: #41 — Your Most Vivid Memories Are Wrong

Ebbinghaus Forgetting Curve
Ebbinghaus Forgetting Curve

If I ask you to remember where you were and what you were doing when you first heard about the September 11, 2001 attacks in New York City, chances are very good that you will be able to tell me in great detail your memory of that day, and how you heard about the attacks. Especially if you live in the US and you were 10 years old or older on that date. But the research shows clearly that you would be wrong about the majority of your memory.

Flashbulb memory is very vivid — Remembering traumatic or dramatic events in great detail is called “flashbulb memory” by psychologists, and has been studied for several decades. Emotions are processed in the amygdala part of the mid-brain, and the amygdala is very close to the hippocampus. The hippocampus is involved in the long term coding of information into memories. So it is no surprise to psychologists that emotionally laden memories might be very strong and remembered vividly.

But the memories are full of errors — It turns out, though, that those memories are full of errors. Ulric Neisser researches memories like these. In 1986 the space shuttle Challenger exploded upon take-off. Any of you reading this who are old enough to remember the Challenger explosion probably remember it vividly, i.e., as a flashbulb memory. Neisser took the opportunity to do some research. The day after the explosion he had his students (he is a professor) write down their memories of what had happened, where they were, what they were wearing, what the TV coverage was like, etc. Three years later he asked them to write down their memory of the event again. Most (over 90%) of the 3-yr later reports differed. Half of them were inaccurate in 2/3 of the details. One person, when shown her first description written three years earlier, on the day after the event, said, “I know that’s my handwriting, but I couldn’t possibly have written that”. Similar research has been conducted on the 9/11 memories, with similar results.

The Forgetting Curve of 1885 — In 1885 Hermann Ebbinghaus created a formula showing the degradation of memories:

Re(−t/S)

where R is memory retention, S is the relative strength of memory, and t is time. The graph at the top of this post is an example of this formula. It’s called the “Forgetting Curve”. Because flashbulb memories are so vivid, it was thought that perhaps they were not as subject to forgetting as other memories. But it turns out they are. Which is kind of disturbing, when you think about it. Because they are so vivid, we are SURE they are accurate and real. But they aren’t nearly as accurate as we think.

Take-Aways – I can think of many ways that we (falsely) rely on people’s memories of events, whether dramatic or not: for example, conducting user or customer research. We often ask customers to remember a particular encounter with a website, software, or an in-store experience. We may have to realize that the memories, although vivid, might not be accurate.

What do you think?  Can you think of situations where you perhaps rely on people’s memories more than you should?

For more reading and information:

Kathryn Schulz, Being Wrong, Harper Collins, 2010

Daniel Schacter, The Seven Sins of Memory, Houghton Mifflin, 2001

Neisser and Harsh, “Phantom Flashbulbs: False Recollections of Hearing the News about Challenger”, in Winograd and Neisser (eds) Affect and Accuracy in Recall, Cambridge University Press, 1992, p. 9-31.

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100 things You Should Know About People: #6 — You Reconstruct Your Memories

Try this task — Think back to a particular event that happened at least 5 years ago. Maybe it was a wedding, or a family gathering, or a dinner you went to with friends, or a vacation. Pick one for our purposes here, and remember the event. Remember the people, and where you were and maybe you can remember the weather, or what you were wearing.

Memories as movies? — We tend to experience our memories of events like this as little movie clips that play back in our minds. And because we experience them this way we have a tendency to think that memories are stored in entirety and never change. But that’s not what happens.

Memories are reconstructed — Our memories are actually reconstructed every time we think of them. They aren’t movie clips that are stored in the brain in a certain location like files on a hard drive. They are nerve pathways that are firing anew each time we remember the event. This makes for some interesting effects. For example, the memory can change.

Subsequent events can affect the memory — Other events that occur after the original event can change the memory of the original event. At the original event, you and your cousin were close friends. But later on you have an argument and a falling-out that lasts for years. Your memory of the first event might include your cousin being aloof and cold, even if that is not true. The later experience has changed your memory.

Mixing events — It is easy to start mixing up memories. So that things that happened at two separate events become fused into one. Your cousin was pleasant at one event, and not pleasant at the other, but over time your memories about which is which can become confused.

Filling in of gaps — You will also start to fill in your memory gaps with “made up” sequences of events, but these will seem as real to you as the original event. You can’t remember who else was at the family dinner, but Aunt Jolene is usually present at these events, and so over time your memory of the event will include Aunt Jolene.

Eyewitness testimony — Elizabeth Loftus is one of the earliest psychology researchers to study reconstructive memory. She was studying eyewitness testimonies, and was especially interested in whether language can affect memory.

Bumped, hit, or smashed — In her research Loftus would show a video clip of an automobile accident. Then she would ask a series of questions about the accident. She would change the way she worded the questions, for example, sometimes she would phrase it as: “How fast would you estimate the car was going when it hit the other vehicle”, or “How fast would you estimate the car was going when it smashed the other vehicle.” And she would ask participants in the study if they remembered seeing broken glass.

You can guess — When she used the word smashed the estimated speed was higher than when she used the word hit. And more than twice as many people remembered seeing broken glass if the word smashed was used rather than the word hit.

So what’s the impact? — Since memories are reconstructed, here are some things to keep in mind:

  • The words you use are important. They can actually affect people’s memories.
  • You can’t rely on self-reports of past behavior. People will not remember accurately what they or others did or said.
  • Watch out for how and what you say if you are interviewing people, for example, interviewing users for a usability or user experience study. You can influence their responses with the words you use.
  • Similarly, take what users say later, when they are remembering using an interface, with a grain of salt. It’s being reconstructed

And if you’d like to read some of Elizabeth Loftus’ seminal work in the area:

Elizabeth F. Loftus and John C. Palmer, Reconstruction of Automobile Destruction:
An Example of the Interaction Between Language and Memory, Journal of Verbal Learning and Verbal Behavior, 13, 585-589 (1974).

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100 Things You Should Know about People: #3 — You Can Only Remember 3 to 4 Things At A Time (The Magic Number 3 or 4)

7 +  –  2???

3 or 4???

Those of you who have been in the field of usability or user experience for a few years have probably heard the phrase “The Magic Number 7 Plus Or Minus 2”. This refers, actually, to what I would call an urban legend. Here’s the legend part:

Legend: “A guy named Miller did research and wrote a research paper showing that people can remember from 5 to 9 (7 plus or minus 2) things, and that people can process 7 plus or minus 2 pieces of information at a time. So you should only put 5 to 9 items on a menu, or have 5 to 9 tabs on a screen”.

Have you heard this? If you’ve been reading about usability for a while I’m sure you have. Well, it’s not quite accurate. Another guy named Baddeley questioned all this urban legend. Baddeley dug up Miller’s paper and discovered that it wasn’t a research paper, it was a talk that Miller gave at a professional meeting. And it was basically Miller thinking out loud about whether there is some kind of inherent limit to the amount of information that people can process at a time.

Baddeley conducted a long series of studies on human memory and information processing. And what he concluded is that the number is 3 to 4, not 5 to 9.

You can remember about 3-4 things (for about 20 seconds) and then they will disappear from memory unless you repeat them over and over. For example, let’s say you are driving in your car and talking on your cell phone (ok, you shouldn’t be doing that) and someone gives you a number to call. But you don’t have a pen handy, and anyway you are driving. So you try to memorize the number long enough to hang up from one call and dial the new number. What do you do? You repeat the number over and over (putting it back into short term memory each time, which buys you another 20 seconds). The interesting thing about phone numbers is that they are more than 3 or 4 numbers long. So they are hard to remember for more than 20 seconds.

712-569-4532

We also tend to chunk information into groups that have 3-4 items in them. So a phone number in the US is: 712-569-4532. Three chunks, with 3-4 items in each chunk. If you know the area code “by heart” (i.e., it’s stored in long term memory), then you don’t have to remember that, so one whole chunk went away. Phone numbers used to be easier to remember because you mainly called people in your area code, so you had the area code memorized (plus you didn’t even have to “dial” the area code at all). And then if you were calling people in your town each town had the same “exchange” — that is the 569 part of the phone number above. So all you had to remember was the last four numbers. No problem! I know I’m “dating” myself here by telling you how it used to be back in the old days. (I live in a small town in Wisconsin, and people here still give their number out as the last four digits only).

But that’s not all! Researchers working in the field of decision-making tell us that people can’t effectively choose between more than 3 to 4 items at a time.

So, what does all this mean? Can you really only have 4 items on a navigation bar? or 4 tabs on a screen, or 4 items on a product detail page at an e-commerce web site? No, not really. You can have more, as long as you group and chunk.

Here’s an example: At the Upton Tea site they have lots of tabs, but the tabs are not chunked into groups of 3 or 4.

So people will tend to do a partial scan and not even look at or read all the tabs. (I love their teas, by the way.. just wish they would do some work on the layout and emotional aspects of their site, but that’s probably another blog!).

I’ve covered more than 4 items in this blog post, so I’ll stop now! For those of you who like to read research here are some references:

  • Baddeley, A. D. (1986). Working memory. New York: Oxford University Press.
  • Baddeley, A. D. (1994). The magical number seven: Still magic after all these years? Psychological Review, 101, 353-356.
  • Miller, G. A. (1956). The magical number seven plus or minus two: Some limits on our capacity for processing information. Psychological Review, 63, 81-97

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