Psychology Topics > Memory


Introduction

From the moment we're born, we're learning. Learning, however, would be useless if we didn't have a way to store all the information we're learning and then access it later. Fortunately, memory takes care of that - memory allows us to process information, store information, and then access it later when we need it.

This may sound very simple, but it's actually quite complex. But have no fear, we'll break it down for you so it's not too tough.

You can think of human memory like a library. The purpose of a library is to store books, magazines, music, and other material. A library has a system of filing and categorizing the materials so they can be retrieved later. If books wear out from excessive use or get lost, they need to be replaced. Libraries obtain new books and materials every year that also need to be filed and categorized. If certain books are rarely used or never retrieved, they are removed to make room for new ones.

We don't know exactly how this process works or where memory is stored, however, researchers believe the parts of the brain that are used in this process are the hippocampus, thalamus, and amygdala. People who have damage to one or all of these areas are not able to store or retrieve information efficiently or even at all.

Hippocampus
The hippocampus is in the temporal lobe of the brain, which is located just above the ears. One of its functions involves spatial memory, i.e. a person's ability to move about in the environment and know where he or she is located. It allows us to travel around in familiar cities or places we live and remember where things are. The hippocampus is also believed to be vital for long term memory. When there is damage done to the hippocampus, the ability to store new information is lost, however, the person can still remember things from before the damage took place.

Thalamus
The thalamus is located above the brain stem which is near the center of the brain. It is like a relay station that receives signals from our senses and then passes the signals to its corresponding area in the cerebral cortex. The thalamus receives signals from all our senses except smell. The thalamus also is responsible for motor control and states of consciousness such as alertness and sleep. The thalamus is important for the retrieval of memory, like the "librarian" of the brain. Not only does it send signals to the right areas of the brain, it is also the relay station to retrieve information later.

Amygdala
The amygdala is also located in the temporal lobe. It is responsible for our emotional perceptions of events. This is important to memory because it associates cues with consequences. When we remember how we felt when something in the past happened, the amygdala is at work. It is also used for the consolidation of long term memory. Researchers have found that the level of emotional arousal a person has when learning something affects its strength in long term memory. The more emotional arousal a person has, the stronger the memory will be.

Short Term Memory
Short term memory allows a person to recall something after a short period of time without practicing or rehearsing. George Miller wrote a paper on short term memory called "The magical number 7 +/- 2." He concluded from his experiments that we could retain 5 to 9 items with our short term memory without rehearsal. The amount can be increased if items are "chunked" together. Most people remember phone numbers in three chunked sets, the area code, the first three numbers, and the last four numbers. After a short period of time, this information degrades and becomes lost unless it is repeated or rehearsed.

Long Term Memory
Long term memory refers to retention of information over the long term from days to years. There are 2 types of long term memory, declarative and procedural. Declarative memory concerns historical events and knowledge of the external world. Procedural memory concerns remembering how to use objects and moving our body. For example, riding a bike would be considered a procedural memory. Remembering something that happened as a child would be declarative memory. Another difference between these two types of long term memory is procedural memory does not require conscious recall, while declarative memory does.

Long term memory is stored in many different places in the brain. Some theorists even believe some memories are stored elsewhere in the body such as the heart. When memory is stored, it tends to cluster together like the librarian in our example categorizes books. Information is connected together to related subjects that are meaningful and relevant to each other. The ways information becomes connected is unique to each person and the experiences they have had. For instance, coconuts remind me of my family. These two subjects may seem unrelated so let's track my thoughts to see how they are connected. If I think about coconuts, I see what the coconut looks like on the outside and inside, I know where it is grown, and I remember what it tastes like. As I remember this information, I think of coconut crème pie. Coconut crème pie is my favorite. Then I remember eating it on my birthday with my family because I don't like cake. This memory in turn brings up other information about my family, and so on.

There is no limit to how much information a person can store in long term memory although various brain disorders and damage can prevent or slow the process. Many techniques can aid and increase the likelihood that information will be retained long term. The next section will illustrate different ways to memorize and strengthen retention of information as well as describe some reasons why we may forget things.

Memory Techniques
The most important factor determining the transfer from short to long term memory is rehearsal. Consider the phrase, "Practice makes perfect." This phrase basically means that our ability is enhanced based on the amount of rehearsal we put in. People use this statement as though practice always results in a positive improvement. However, if we rehearse something incorrectly, we will get better.... at doing it incorrectly! Therefore, taking things slow and learning things correctly the first time is an important technique. It is harder to change inaccurate information and or behaviors once they have been stored in long term memory, e.g. habits.

Another important factor to consider when looking at practice is the time frame in which the practice occurs. Smaller increments of practice over time are stronger than "cramming" in one night. Anyone who has tried this method for test taking has learned that the hard way.

As stated before, emotions connected with memories also strengthen retention. Memories of trauma are very strong because of the emotions attached to them. This does not mean these memories are always completely accurate representations of what happened, however, because perceptions and other factors influence our memory and they can slowly change over time. Have you ever heard of someone catching a fish and the fish somehow gets bigger every time the story is told?

Other techniques for enhancing memory consist of using more than one of our senses to rehearse information. For example, reading a vocabulary list out loud will strengthen retention more than reading the list on the paper. Putting information together in meaningful ways such as poems, clusters, music or even rhythms also improve retention as well as retrieval of the information later. This explains why memorizing a list of nonsensical words is more difficult than remembering words that have meanings.

Memory is also strengthened by making connections and associations between new information and previously learned information. The more associations are made, the easier the information is to remember and access. Going back to our library analogy, books are easier to find when they are connected to more than one category. Therefore, if we learn a concept and then connect it will similar things we already know and distinguish it from opposites, we will be able to remember it better.

Don't forget about forgetting
When we forget things, it is often a problem of encoding. Perhaps we were distracted while trying to learn information or while we were doing something. For instance, how many times you have lost your keys or misplaced the remote control? Perhaps you were thinking about something else when you put your keys down. Distraction reduces encoding efficiency while memory requires conscious attention. Thus, distraction explains why you put your keys in the refrigerator and threw the remote control in the garbage can.

Perhaps you weren't distracted but also didn't make enough associations to strengthen the memory of where you put your keys. This leads to an inability to retrieve the memory of where you left them. You may be able to imagine several possible places they could be but can't quite remember which. A common solution to this is to "retrace your steps." In essence, "retracing your steps" goes through all the associated locations in your mind until you find the correct one that is connected to the keys' location.

Disorders that affect memory
Alzheimer's: Alzheimer's is a disease of the elderly (usually seen in patients aged 65 or older) in which the brain slowly degenerates. The symptoms are confusion, memory loss, problems with verbal expression, emotional liability (means they switch moods frequently), and a progressive loss of bodily control that leads to death. In the advanced stages of Alzheimer's, patients are unable to recognize significant others, they may wander off aimlessly, and they are not able to care for themselves.

Dementia: Dementia is defined as the loss of previous cognitive ability and function. It is a name of a symptom rather than an actual disorder. For instance, Alzheimer's is a disease that includes dementia as a symptom. People with dementia may have damage to long term memory, short term memory, or both.

Huntington's Disease: Huntington's is a degenerative disease that affects muscle coordination as well as cognitive impairment. It is usually diagnosed in between 35 and 44 years of age. The symptoms are jerky movements or abnormal posturing, personality changes, dementia, general physical instability, sleeping problems, and seizures.

Parkinson's Disease: Parkinson's Disease is a degenerative disease of the central nervous system (the system responsible for coordination of movement). The symptoms are stiffness, tremor, and slowing of movement. Patients may or may not experience loss of cognitive abilities such as memory. Many people experience a slowing of cognitive function and others progress into dementia.

Schizophrenia: Schizophrenia is a disease most known for symptoms of visual and auditory hallucinations, however, it also involves many other cognitive deficits. Some of these symptoms are delusions, inability to experience pleasure, problems with memory, language, and problem solving to name a few. People suffering from schizophrenia believe in their delusions and or hallucinations so strongly because they are unable to distinguish true memories and reality from their symptoms of unreality. If you have ever had someone try to tell you something you remembered didn't really happen, you are a little closer to understanding how schizophrenia feels.

Key Figures & Theories

George Armitage Miller
George Armitage Miller is noted for writing the famous paper, "The magic number 7 plus or minus 2." In his paper, Miller proposed that people can hold from 5-9 items in short term memory without rehearsal. Miller coined the term "chunking," a technique used to keep more information in short term memory by clustering pieces of information together in a meaningful way. For instance, it is easier to remember three chunks of numbers 362, 109, and 597 than it is to remember each number individually, e.g. 3, 6, 2, 1, 0, 9, 5, 9, 7.

Miller also helped create wordnet. Wordnet is a database for the English language that groups words into sets of synonyms. How these words are grouped is more complicated than will be explained here, but the purpose of the wordnet was to devise a model for how we store, process, and access language or semantics in the brain.

Atkinson and Shiffrin
Richard Atkinson and Richard Shiffrin were psychologists who collaborated to formulate their own model of memory. Their theory (the Atkinson-Shiffrin model) proposed that memory consisted of 3 stages; sensory memory, short term memory, and long term memory. They believed that first, we take in information through our senses (sensory memory). The information is retained for a matter of seconds before it degrades and disappears. If, however, this information is rehearsed or repeated, it is transferred to short term memory. The length of time information can remain in short term memory varies from person to person. If the information is repeated, it will stay in short term memory longer before it degrades and disappears. If the information is rehearsed enough times, it is transferred to long term memory.

Alan Baddeley and Graham Hitch
Baddeley and Hitch collaborated to propose a memory theory called the model of working memory. They described the concept of working memory as having 4 parts; central executive, phonological loop, visuo-spatial sketchpad, and episodic buffer. The phonological loop, also called an articulation loop, consists of auditory memory traces that degrade quickly. In simpler words, if we hear something, we will forget it quickly unless we rehearse or repeat what we have heard. Rehearsing refreshes the memory traces before it disappears.

The visuo-spatial sketchpad is like the phonological loop except it concerns things we see. The episodic buffer connects spatial, visual, and verbal information in chronological order. This allows us to remember pieces of a storyline in the correct order. The central executive controls all these components. It allows us to change from storing information to retrieving information or switching between tasks. It binds information together in meaningful ways, allows selective attention, and inhibits other thoughts or behaviors when needed. Another way of thinking about working memory is that we use working memory to manipulate information while we learn and complete tasks. The retention of working memory is longer than short term memory and through working memory, we decide what information needs to be transferred to long term memory.

Elizabeth Loftus
Elizabeth Loftus studies and research concern the validity of eye witness testimony and "False Memory Syndrome," the idea being that therapists convince clients that they have repressed memories of childhood abuse when in reality, they do not. Loftus also did research on the accuracy of eye witness accounts of events. In her experiment, she had people watch a video of an automobile accident. Afterwards, she asked them how fast the cars were traveling when they collided? She asked this question in different ways by replacing the verb "collided" with other verbs "smashed," "hit," "contacted," etc. Loftus found that the verb used influenced how the people in the study responded.

In a similar study, Loftus hypothesized that eye witnesses could be manipulated to remember things that were inaccurate if they were asked leading questions. In this experiment, she showed a video of an accident and then asked if the person saw any broken glass? Several people reported they had seen broken glass in the video even though there wasn't any. Therefore, Loftus concluded that eye witness testimony was not reliable.