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Memory

Your memory is divided into short-term memory and long-term memory. Your short-term memory remembers most new information for less than 20 seconds1. Even if you make a conscious effort to remember something, you’ll probably forget half of it within an hour2. Working memory is the ability of your short-term memory to think about multiple items of information at the same time. Its capacity is only about 3–4 items at the same time3.

This underwhelming fact was discovered when volunteers were presented with a display of 1–8 colored disks on a computer screen. After a 1,200 millisecond delay, they were shown a second set of disks, and asked whether it matched the first set for color and location. Performance declined past three or four disks. This is why telephone numbers are split into groups of three or four numbers. The average person finds this easier to remember than a string of seven digits.

Take Notes
It takes a lot of mental effort to hold things in memory. Give your brain a break. Write down the information and save your brainpower. Try this simple method:
  1. Place pens and notepads on your desk, beside your bed, and inside your car.
  2. Whenever you get an interesting thought or idea, write it down immediately.
  3. Alternatively, use your cell phone to record voice memos for yourself.

“The horror of that moment,” the King went on, “I shall never, never forget!”
“You will, though,” the Queen said, “if you don’t make a memorandum of it.”

-Lewis Carroll, Alice’s Adventures in Wonderland

Types of Information
In contrast to your short-term memory, your long-term memory is capable of storing about 100 million items of information4. In other words, its capacity is practically unlimited. How can you improve the transfer of information from short-term to long-term memory? The first step is realizing that your memory actually distinguishes between three types of information5:
  1. Memory for arbitrary things
  2. Memory for meaningful relationships
  3. Memory through explanation
There’s no rhyme or reason behind arbitrary things. It’s like pressing “Ctrl-Alt-Del” to restart your computer. One day, some programmer just decided on that particular combination of three keys. It takes a lot of time and effort to memorize arbitrary things. And if you forget, there’s no hint to help you remember.

In contrast, it’s much easier to remember something if it has a meaningful relationship with something you already know. It’s easier to remember your friend’s birthday if it’s on Valentine’s Day. It also helps if there’s an explanation or fundamental principle behind what you’re trying to remember—you’re more likely to remember that Venus is the name of the planet between Earth and Mercury if you know that all the planets are named after Roman gods.

A good memory constitutes about 70 percent of what commonly passes for genius.
-Hesketh Pearson

Mnemonics
The most common way to memorize arbitrary things is to repeat them over and over and over again. Repetition strengthens connections between brain cells and solidifies memory6. But repetition is boring and takes a lot of time. Mnemonics are faster than repetition. A mnemonic is a memory aid, such as a formula or rhyme, which makes things easier to remember. It establishes a meaningful link between unrelated things. Think of the song that kids sing to remember the order of letters in the alphabet. Or the phrase, “Man Very Early Made Jars Stand Up Nearly Perfectly” for the names and order of planets in the solar system.

Visualization
A more advanced mnemonic is the “Look, Snap, Connect” technique described by psychiatrist Gary Small in his book The Memory Bible7. The three steps are:
  1. Look: carefully observe what you want to remember.
  2. Snap: create a vivid mental snapshot of the image.
  3. Connect: imagine a link between images.
Suppose you want to remember the three words: “Bill Clinton,” “umbrella,” and “lobster.” With the “Look, Snap, Connect” technique, you might visualize Bill holding a neon orange umbrella to shield him from a rain of red lobsters, their claws frantically waving as they fall out of the sky.

Look, Snap, Connect
  1. At breakfast, pick three items to memorize (e.g., apple, cup, spoon).
  2. Create a vivid mental image linking the three objects.
  3. Before you go to bed, recall the image and remember the three items.

Mental Walk
Every year, the world’s best memorizers compete in the World Memory Championships (WMC). Past winner Ben Pridmore has performed incredible feats, such as memorizing the order of a randomly-shuffled deck of cards in 36 seconds, and recalling 170 names and faces after studying them for only 15 minutes. How does Ben do it?

To answer this question, researchers studied 10 competitors from the WMC and other memory contests8. Neuropsychological tests showed that superior memory was not associated with superior intelligence. Also, brain scans of top memorizers showed no anatomical differences when compared to those of regular people. Instead, researchers discovered that all of the memorizers used mnemonics. Nine out of 10 used the “method of loci” or “mental walk” technique, first described by the Greek poet Simonides of Ceos in 477 BC. It associates items to be remembered with specific points along a known route, which are then recalled as you mentally retrace your steps.

For example, on the route from your desk to the bathroom, you might associate “Bill Clinton” with a desk lamp, “umbrella” with a potted plant, and “lobster” with a door handle. To remember what you’ve memorized, you mentally walk back along the path, and recall the items as you pass the memory points.

Testing Effect
Whether you’re memorizing arbitrary things or meaningful relationships, a phenomenon known as the “testing effect” can speed up your learning. In a study from Washington University, students were split into three groups and asked to memorize 250 words of text9. The first group studied for four periods of 7 minutes each. They took rest breaks of 2–5 minutes between study periods. The second group studied for three 7-minute periods, and completed a 7-minute practice test. The third group studied for one period, and completed three practice tests.

One week later, all of the students were given a memory recall test. The first group remembered 48 percent of the items, compared to 72 percent for the second group, and 86 percent for the third group. Doing a practice test is more effective than studying longer.

Practice Tests
The testing effect helps you memorize more in less time. Here are some sources of practice tests:
  1. After each lecture or study session, write down a list of questions. On a separate sheet, write down the model answers. Quiz yourself a few times a week.
  2. Ask your teacher or upper-year students for old tests from previous years. Do them and pay special attention to questions you get wrong.
  3. Find a study partner and quiz each other. Compete to see who gets the most right answers.

Body and Brain
Our brains comprise 2 percent of our body weight, but use 40 percent of our blood glucose. They’re like gas-guzzling SUVs—they need lots of fuel to run. In a study from the University of British Columbia, low blood sugar levels made it harder for people to count backwards in sevens10. In another study from Tufts University, kids ate either oatmeal or a sugary cereal for breakfast11. After eating, they were given tasks such as memorizing the names of countries on a map. The oatmeal eaters performed up to 20 percent better than the sugary cereal eaters.

Oatmeal contains protein and fiber, and releases glucose at a steady rate into the bloodstream. In contrast, sugary cereal is digested quickly and spikes blood sugar levels. To mop up the excess sugar, your body overcompensates and releases too much insulin. This leads to a crash in blood glucose, and impairs your memory. For optimal performance, fuel your brain with healthy food. Avoid sugary snacks like chocolate, candy, and cake.

In addition to good nutrition, your brain works better when it’s relaxed. Stress makes it harder to remember. Researchers at Washington University injected volunteers with cortisol, a stress hormone12. Volunteers received an amount corresponding to a moderate level of stress. Researchers found that subjects with high-average memory dropped to average, and those with low-average memory dropped to borderline. The next time you’re stressed out, take a deep breath and relax. Go for a walk and clear your mind.

References
  1. Bernstein DA et al. (1988). Psychology. Houghton Mifflin. p. 293.
  2. Ebbinghaus H. (1964). Memory. Translated by HA Ruger and CE Bussenius. Dover Publications. p. 76.
  3. Todd JJ, Marois R. (2004). Capacity limit of visual short-term memory in human posterior parietal cortex. Nature. 428:751–754.
  4. Landauer TK. (1986). How much do people remember? Some estimates of the quantity of learned information in long-term memory. Cognitive Science. 10:477–493.
  5. Norman DA. (1988). The design of everyday things. Basic Books.
  6. Colicos MA et al. (2001). Remodeling of synaptic actin induced by photoconductive stimulation. Cell. 107:605–616.
  7. Small G. (2002). The memory bible: an innovative strategy for keeping your brain young. Hyperion.
  8. Maguire EA et al. (2003). Routes to remembering: the brains behind superior memory. Nature Neuro. 6(1):90–95.
  9. Roediger, III HL, Karpicke JD. (2006). Test-enhanced learning: taking memory tests improves long-term retention. Psychological Science. 17(3):249–255.
  10. Taylor LA, Rachman SJ. (1988). The effects of blood sugar level changes on cognitive function, affective state, and somatic symptoms. Journal of Behavioral Medicine. 11(3):279–291.
  11. Mahoney CR et al. (2005). Effect of breakfast composition on cognitive processes in elementary school children. Physiology & Behavior. 85:635–645.
  12. Newcomer JW et al. (1999). Decreased memory performance in healthy humans induced by stress-level cortisol treatment. Arch Gen Psych. 56(6):527–533.

Copyright © 2009 by Paul Lem, M.D.
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