Long-Term Memories and How They Are Stored
Your long-term memory is the final destination. Because it is unable to be measured, the long-term memory is thought to have an infinite capacity. You already have a vast amount of information stored there and are continuously storing more every day. For instance, your activities of daily living are reliant upon the memories stored in long-term memory. At some point you learned how to shower, brush your teeth, dress yourself, make coffee, drive the route to work, do your job, make dinner, and set the alarm clock. The memories of how to do all these things are retrieved from the long-term memory, even though you may not be conscious of the retrieval. Of course, this isn't the only type of information stored; past experiences that make up your personal history and give you a sense of identity are stored here as well.
Storing and Organizing Information
While the long-term memory holds a great amount of knowledge, it is not just a jumble of bits of information swimming around in chaos. There is an organizational system present that helps both to store and retrieve memories.
When a memory enters long-term memory, it makes associations with memories already present. For instance, words are stored next to other words in your long-term memory that are similar in meaning, sound, or look. To help break it down even further, your mind creates categories for words, so apple and peach would be stored close to one another since they are both fruits. Chair and table would be stored next to each other since they are both items of furniture. Shirt and skirt would be stored close together because they are both articles of clothing. You get the picture. Items can belong to more than one category — for instance, you might want to remember all the pieces of clothing, jewelry, or shoes that you own that are black, in order to put together an outfit.
As oral storytelling was once the primary way of recording history before the written word, several cultures relied on the long-term memory of their members to recant and pass on these stories. The Odyssey and the Iliad, for instance, were both originally oral epic poems that didn't get written down until long after they were composed.
The associations made are very important for both storage and retrieval. If your mind is able to associate a new concept or word with a memory already in long-term, then storage is made easy. Retrieval is easier as well, because as you are searching for that concept or word, your mind can look to the associations for help in bringing it to the consciousness.
Categories of Memories
The long-term memory is able to divide types of memories into three basic categories: procedural memories, episodic memories, and semantic memories. Procedural memories are those that provide information on how to do things. For example, riding a bike, brushing your teeth, tying your shoes, and driving are all procedural memories. Typically, this type of memory becomes so ingrained that it requires very little conscious retrieval or thought to carry out the activity. In other words, procedural memories are implicit.
Episodic memories are those that allow you to recall events and situations that you have experienced. Along with the event itself, the circumstances surrounding the event (location, time, etc.) are also stored. Closely related to episodic memory is autobiographical memory — that is, the memory of your own personal life history. This type of memory plays an essential role in your unique sense of self. Semantic memories are basically facts you have learned — the date of your father's birthday, the meanings of words, your address, who invented the cotton gin, and so on. Episodic and semantic memories are both types of explicit memories. They must be consciously retrieved from long-term memory.