At the beginning of every New Year, the media summarize (remember) the events of the previous year. We would be hard pressed to recall many of these events, but we instantly recognize most of them when they are mentioned in the media. Why do we have trouble remembering some events?
First of all, memory is not just one process. Incoming information first enters sensory memory – which holds an exact copy of what was seen or heard for a few seconds or less. Any image you see – an icon ("EYE-kon") – last for about a half-second. To see an icon, hold your hand in front of your face. If you rapidly blink your eyes, you will see your hand a split-second after closing your eyes. Sensory memory for sound – an echo – lasts for up to two seconds.
Depending on your selective attention, some information can be transferred to your short-term memory (STM). This is also called your working memory. In fact, what you are thinking about now as you read this article is in your STM. However, this memory only stores a limited amount of information – seven chunks of information for most people – for a limited amount of time – less than 20 seconds. The best analogy for STM is a "leaky bucket." As water (information) is put into the bucket (STM), it quickly leaks out, making room for more water. This allows us to quickly forget unimportant information.
Rehearsal– repeating the new material over and over – allows us to keep the information in STM. This is like catching the water as it leaks out and pouring it back into the bucket again. However, while we are rehearsing, it is difficult to get any new information into the STM. Also, if anything distracts us, the information we are rehearsing will probably be lost.
However, if we canrecode some information, it can be deposited into relatively permanent memory called long-term memory (LTM). As new long-term memories are formed, older ones are often updated, changed, lost or revised. Even then, it depends on which type of LTM is utilized.
The type of LTM that stays with us best isprocedural or skill memory. These include various tasks such as typing, riding a bicycle, solving a puzzle or swinging a golf club. Essentially, these memories can only be fully expressed as actions. People who have amnesia – temporary or permanent memory loss – typically have trouble remembering various facts like telephone numbers, addresses or names. The may also have trouble learning and remembering new ones. However, they can solve complex puzzles in the same time that it takes normal subjects.
Rather than procedural memory, amnesia seems to effect fact memory to a greater extent.Fact memory is the ability to learn specific information, such as names, dates, faces, words or ideas. This is the memory that a person with amnesia lacks, and most of us take for granted. Some psychologists believe that fact memory can be further subdivided into two other subtypes.
Most of our factual knowledge about the world is overlearned and almost immune to forgetting. The names of objects, the days of the week or months of the year, simple math skills, words and language, and other general facts are all quite lasting. These facts make up the part of LTM calledsemantic memory – which serves as a mental dictionary or as an encyclopedia of basic knowledge.
However, semantic memory has no connection to specific times and places. For example, do you know when and where you learned the names of the seasons of the year? In contrast,episodic memory ("ep-ih-SOD-ik") is "autobiographical." It records the life events (episodes) that happen to us day after day, year after year. Can you remember your seventh birthday, the ideas you have read in this article, or what you had for breakfast three days ago? All of these are episodic memories.
Generally, episodic memories are more easily forgotten than semantic memories. This is because new information constantly pours into episodic memory. Stop for a moment and try to recall what you did last summer. That was an episodic memory. Notice that you now remember that you remembered something. Now you are having a new episodic memory – you remembered that you remembered something while you were reading this article! With this example, it is easy to see how much we ask of our memory system.
To get into our LTM, information must be noticed, encoded and stored. However, memory also involves retrieval – getting information out when we want it. Memory problems often involve retrieving the memories that have been stored. I'm sure that you have had these problems once in a while. Some information is just out of reach – "on the tip of your tongue" so to speak – but you are absolutely sure that you know the information. Often you can give the first or last letter of the answer, the number of syllables, or even what it sounds like – but still draw a blank. However, sometime later (usually too late), it finally comes to you.
If you don't remember some of the events that occurred in the past year – this doesn't mean that you are losing your memory. It is merely that so many new things have been encoded in your episodic memory, you can't keep track of all the current events. A week or so after you have read this article, you probably won't even remember that you have an episodic memory!
* Adapted from Dennis Coon's Introduction to Psychology: Exploration and Application, West Publishing, 1986, pages 234-257.
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