10 Facts About Memory

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10 Interesting Things You Should Know About Memory

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Our memory helps make us who we are. From fondly recollecting childhood events to remembering where we left our keys, memory plays a vital role in every aspect of our lives. It provides us with a sense of self and makes up our continual experience of life.

It's easy to think of memory as a mental filing cabinet, storing away bits of information until we need them. In reality, it is a remarkably complex process that involves numerous parts of the brain. Memories can be vivid and long-lasting, but they are also susceptible to inaccuracies and forgetting.

Continue reading to learn more about some of the most interesting aspects of human memory.

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The Hippocampus Plays an Important Role In Memory

hippocampus and memory
The hippocampus is a region of the brain that is heavily associated with memory. Because of bilateral symmetry in the brain, both hemispheres contain a hippocampus. Image courtesy Wikimedia Commons

The hippocampus is a horse-shoe shaped area of the brain that plays an important role in consolidating information from short-term memory into long-term memory. It is part of the limbic system, a system associated with emotions and long-term memories. The hippocampus is involved in such complex processes as forming, organizing, and storing memories.

Because both sides of the brain are symmetrical, the hippocampus can be found in both hemispheres. Damage to the hippocampus can impede the ability to form new memories, known as anterograde amnesia.

Functioning of the hippocampus can also decline with age. By the time people reach their 80s, they may have lost as much as 20 percent of the nerve connections in the hippocampus. While not all older adults exhibit this neuron loss, those who do show decreased performance on memory tests.

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Most Short-Term Memories Are Quickly Forgotten

Hands of man holding telephone number on torn paper, trying to memorize number
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The total capacity of short-term memory is fairly limited. Experts believe that you can hold approximately seven items in short-term memory for about 20 to 30 seconds. This capacity can be stretched somewhat by using memory strategies such as chunking, which involves grouping related information into smaller "chunks."

In a famous paper published in 1956, psychologist George Miller suggested that the capacity of short-term memory for storing a list of items was somewhere between five and nine. Today, many memory experts believe that the true capacity of short-term memory is probably closer to the number four.

See this in action for yourself by trying out this short-term memory experiment. Spend two minutes memorizing a random list of words, then get a blank piece of paper and try to write down as many of the words that you can remember.

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Being Tested On Information Actually Helps You Remember It Better

Memory and test taking
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While it may seem like studying and rehearsing information is the best way to ensure that you will remember it, researchers have found that being tested on information is actually one of the best ways to improve recall.

One experiment found that students who studied and were then tested had better long-term recall of the materials, even on information that was not covered by the tests. Students who had extra time to study but were not tested had significantly lower recall of the materials.

5
You Can Learn to Improve Your Memory

Smiling businessman arranging adhesive notes on whiteboard to aid memory
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Do you ever feel like you are constantly forgetting things or misplacing objects that you use every day? Have you ever found yourself walking into a room only to realize that you can't remember why you went in there in the first place? While it might seem like you are doomed to simply tolerate these daily annoyances, researchers have found that you can learn how to improve your memory.

A 2005 cover story in the Monitor on Psychology summarized research revealing a number of useful strategies to deal with mild memory loss. These techniques include:

  • Utilizing technology to keep track of information. Tools such as hand-held mobile devices and online reminder calendars can help people keep track of appointments and other important dates. Using a reminder app on your phone can be a handy way to stay on top of important dates and events.
  • Taking a "mental picture" can help. Systematically trying to make a mental note of things you often forget (such as where you left your car keys) can help you remember things better. The next time you set your keys down somewhere, take a moment to mentally note where you left them as well as the other objects that were nearby. If you think to yourself "I left my keys by my wallet on the desk," you'll probably find it easier to recall the information later.
  • Use memorization techniques. Rehearsing information, employing mnemonics, and other memorization strategies are perhaps the best ways to overcome minor memory problems. By learning how to use these strategies effectively, you can sidestep the faulty areas of your memory and train your brain to function in new ways.

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There Are Four Major Reasons Why You Forget Things

Reasons for Forgetting
Forgetting can occur for many reasons, including interference from other memories. Photo by Julia Freeman-Woolpert

In order to combat forgetfulness, it is important to understand some of the major reasons why we forget things. Elizabeth Loftus, one of the world's most renowned experts on human memory, has identified four major reasons why forgetting occurs. One of the most common explanations is a simple failure to retrieve the information from memory. This often occurs when memories are rarely accessed, causing them to decay over time.

Another common cause of forgetting is interference, which occurs when some memories compete with other memories. For example, imagine that a woman just started a new school year as an elementary school teacher. She spends some time learning the names of each of her students, but over the course of the year she finds herself constantly calling one particular girl by the wrong name. Why? Because the girl's older sister was in the same class the year before, and the two look remarkably similar. It is the memory of the older sister that makes it so difficult to recall the younger student's name.

Other causes of forgetting include failing to store the information in memory in the first place, or even intentionally trying to forget things associated with a troubling or traumatic event.

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Depictions of Amnesia in Movies Are Usually Inaccurate

amnesia in movies
Amnesia: Not Like it Is in the Movies. Photo by Ryan Baxter - http://www.flickr.com/photos/15225700@N06/2427008704

Amnesia is a common plot device in the movies, but these depictions are often wildly inaccurate. For example, how often have you seen a fictional character lose their memory due to a bump on the head only to have their memories magically restored after suffering a second knock to the skull?

There are two different types of amnesia:

  • Anterograde amnesia: Involves the loss of the ability to form new memories.
  • Retrograde amnesia: Involves losing the ability to recollect past memories, although the ability to create new memories may remain intact.

While most movie depictions of amnesia involve retrograde amnesia, anterograde amnesia is actually far more common. The most famous case of anterograde amnesia was a patient known in the literature as H.M. In 1953, he had brain surgery to help stop the seizures caused by his severe epilepsy. The surgery involved the removal of both hippocampi, the regions of the brain strongly associated with memory. As a result, H.M. was no longer able to form any new long-term memories.

Popular movies and television programs tend to depict such memory loss as fairly common, but true cases of complete amnesia about one's past and identity are actually quite rare.

Some of the most common causes of amnesia include:

  • Trauma: A physical trauma, such as a car accident, can cause the victim to lose specific memories of the event itself. Emotional trauma, such as being a victim of childhood sexual abuse, can cause the individual to lose memories of specific situations.
  • Drugs: Certain medications can be used to cause temporary amnesia, particularly during medical procedures. Once the drugs wear off, the individual's memory returns to normal functioning.

Films Containing Depictions of Amnesia

  • Robocop (1987)
  • Regarding Henry (1991)
  • The English Patient (1996)
  • Memento (2001)
  • The Bourne Identity
  • 50 First Dates (2004)
  • Finding Nemo (2003)

The science blog Neurophilosophy points out two fairly recent films that contain fairly accurate depictions of amnesia: Memento and Finding Nemo.

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Scent Can Be a Powerful Memory Trigger

Smell and Memory
The sense of smell can help evoke powerful and vivid memories. Photo by Sandi Hanna

Have you ever noticed that a particular scent can bring forth a rush of vivid memories? The smell of cookies baking might remind you of spending time at your grandmother's house when you were a small child. The scent of a particular perfume might remind you of a romantic partner with whom your relationship ended on a sour note.

Why does smell seem to act as such a powerful memory trigger?

First, the olfactory nerve is located very close to the amygdala, the area of the brain that is connected to the experience of emotion as well as emotional memory. In addition, the olfactory nerve is very close to the hippocampus, which is associated with memory as you learned earlier in this article.

The actual ability to smell is highly linked to memory. Research has shown that when areas of the brain connected to memory are damaged, the ability to identify smells is actually impaired. In order to identify a scent, you must remember when you have smelled it before and then connect it to visual information that occurred at the same time. According to some research, studying information in the presence of an odor actually increases the vividness and intensity of that remembered information when you smell that odor again.

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New Brain Connections Are Created Every Time You Form a Memory

Synapses and Memory
Diagram of a synapse. Photo from the Wikimedia Commons

Researchers have long believed that changes in brain neurons are associated with the formation of memories. Today, most experts believe that memory creation is associated with the strengthening of existing connections or the growth of new connections between neurons.

The connections between nerve cells are known as synapses, and they allow information carried in the form of nerve impulses to travel from one neuron to the next. In the human brain, there are trillions of synapses forming a complex and flexible network that allows us to feel, behave, and think. It is the changes in the synaptic connections in areas of the brain such as the cerebral cortex and hippocampus that is associated with the learning and retention of new information.

In one study conducted at the New York School of Medicine, researchers were able to observe synapse formation in the brains of genetically engineered mice. What they discovered was that in young mice, the tiny protrusions that sometimes develop into longer spines on the receiving end of neurons grew at a rapid rate. This growth rate coincided with the rapid development of the visual cortex. While a large number of these tiny protrusions eventually faded with age, many did continue their formation into fully-fledged spines.

Lead researcher Wen-Biao Gan explained in an interview with the science website WhyFiles.org, "Our idea was that you actually don't need to make many new synapses and get rid of old ones when you learn, memorize. You just need to modify the strength of the preexisting synapses for short-term learning and memory. However, it's likely that few synapses are made or eliminated to achieve long-term memory."

Clearly, maintaining a healthy brain and synapses is critical. Deterioration of synapses due to diseases or neurotoxins is associated with cognitive problems, memory loss, changes in mood, and other alterations in brain function.

So what can you do to strengthen your synapses?

  • Avoid stress: Research has found that extended exposure to stress can actually interfere with neurotransmitter function. Other studies have found that stress shrinks neurons in the prefrontal cortex and hippocampus.
  • Avoid drugs, alcohol, and other neurotoxins: Drug use and excessive alcohol consumption have been linked to synaptic deterioration. Exposure to dangerous chemicals such as heavy metals and pesticides can also cause synaptic loss.
  • Get Plenty of Exercise: Regular physical activity helps improve oxygenation of the brain, which is vital for synaptic formation and growth.
  • Stimulate your brain: You've probably heard the old adage "Use it or lose it." Well, it turns out there's a lot of truth to that when it comes to memory. Researchers have found that elderly adults who engage in mentally stimulating activities are less likely to develop dementia and people with higher educational statuses tend to have more synaptic connections in the brain.

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A Good Night's Sleep May Improve Your Memory

Sleep and Memory
Sleep can actually help improve your memory. Photo by Mayr / http://www.flickr.com/photos/mayr/

You have probably heard about many of the reasons to get a good night's sleep. Since the 1960s, researchers have noted the important connection between sleep and memory. In one classic experiment conducted in 1994, researchers found that depriving participants of sleep impaired their ability to improve performance on a line identification task.

In addition to aiding in memory, sleep also plays and essential role in learning new information. In one study, researchers found that depriving students of sleep after learning a new skill significantly decreased memory of that skill up to three days later.

Researchers have found, however, that sleep's influence on procedural memory is much stronger than it is for declarative memory. Procedural memories are those that involve motor and perceptual skills, while declarative memories are those that involve the memorization of facts.

"If you're going to be tested on 72 irregular French verbs tomorrow, you might as well stay up late and cram," explained Robert Stickgold, a psychiatry professor at Harvard Medical School, in an article published in the APA's Monitor on Psychology. "But if they're going to throw a curveball at you and ask you to explain the differences between the French Revolution and the Industrial Revolution, you're better off having gotten some sleep."

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Memory Failure in Old-Age Might Not Be Inevitable

Senior looking at photo memory
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While Alzheimer's disease and other age-related memory problems affect many older adults, the loss of memory during old-age might not inevitable. Certain abilities do tend to decline with age, but researchers have found that individuals in their 70s often perform just as well on many cognitive tests as do those in their 20s. Some types of memory even increase with age.

While researchers are still working to understand why exactly some elderly adults manage to maintain an excellent memory while other struggle, a few factors have been implicated so far. First, many experts believe that there is a genetic component to memory retention during old age. Secondly, lifestyle choices are also believed to play an important role.

"I think it's a nature-nurture interaction, in large part," Dr. Bruce S. McEwen, a professor at Rockefeller University in New York, explained to The New York Times. "'A genetic vulnerability increases the likelihood that experience will have an effect."

So what are some steps you can take to stave of the negative effects of aging?

According to one decade-long study, having a strong sense of self-efficacy has been associated with maintaining good memory abilities during old age. Self-efficacy refers to the sense of control that people have over their own lives and destiny. This strong sense of self-efficacy has also been linked to lowered stress levels. As mentioned previously, high levels of chronic stress have been connected to deterioration in the memory centers of the brain.

While there is no simple "quick fix" for ensuring that your memory stays intact as you age, researchers believe that avoiding stress, leading an active lifestyle, and remaining mentally engaged are important ways to decrease your risk of memory loss.

References

Adelson, R. (2005). Mending memory. Monitor on Psychology. APA. http://apa.org/monitor/sep05/mending.aspx

Chan, J.C., McDermott, K.B., & Roediger, H.L. (2007). Retrieval-induced facilitation. Journal of Experimental Psychology: General, 135(4), 553-571.

Carroll, L. (2000). Is memory loss inevitable? Maybe not. The New York Times. http://www.nytimes.com/2000/02/01/health/is-memory-loss-inevitable-maybe-not.html?src=pm

Di Gennaro, G., Grammaldo, L.G., Quarato, P.P., Esposito, V., Mascia, A., Sparano A, Meldolesi, G.N., Picardi, A. (2006). Severe amnesia following bilateral medial temporal lobe damage occurring on two distinct occasions. Neurological Sciences, 27(2), 129–33.

Herz R.S. & Engen T.1996. Odor memory: review and analysis. Psychonomic Bulletin and Review 3, 300-313.

Jacob, T. Olfaction: A tutorial on the sense of smell. http://www.cf.ac.uk/biosi/staffinfo/jacob/

Toberen, A. (2003). Learning: It's a memory thing. WhyFiles.org. http://whyfiles.org/184make_memory/index.html

Miller, G. A. (1956), The magical number seven, plus or minus two: Some limits on our capacity for processing information, Psychological Review 63 (2): 343–355

Mohs, Richard C. (2007). How human memory works. HowStuffWorks.com. http://health.howstuffworks.com/human-body/systems/nervous-system/human-memory.htm

Monnell Center. Advancing discovery in taste and smell. http://www.monell.org/

Most people with amnesia forget all details of their earlier lives. (2010). Excerpted from 50 Great Myths of Popular Psychology: Shattering Widespread Misconceptions about Human Behavior by Scott O. Lilienfeld, Steven Jay Lynn, John Ruscio, and Barry L. Beyerstein. http://www.psychologicalscience.org/media/myths/myth_14.cfm

Want to improve memory? Strengthen your synapses. Here's how. Medical News Today. http://www.medicalnewstoday.com/articles/60455.php

Winerman, L. (2006). Let's sleep on it: A good night's sleep may be the key to effective learning, says recent research. Monitor on Psychology. http://www.apa.org/monitor/jan06/onit.aspx

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