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Breaking down memory

November 6, 2011

In spite of the title, this post is not about memory break-down. However, in order to talk about my work, which has focused on semantic memory (including its break down in semantic dementia), I felt like I should start by talking about the different types of memory which exist.

So, starting off broadly and working toward more specific forms, I will start with non-declarative and declarative memory.

A non-declarative memory is a memory which we are not consciously aware of, but which influences our behaviour. There are at least two forms of non-declarative memory: procedural and implicit memory.

Procedural memory: I will start with procedural memory because it is a bit easier to understand. For example, can you explain how you keep your balance when riding a bicycle? Or can you describe how you tie your shoes? Or how to walk? It would probably be difficult to tell someone how to carry out these tasks, but most adults have no problem doing these things on a daily basis. This is because our ability to carry out these tasks is based on procedural, or motor skill memory, more than on conscious recall. In other words, they are not things which you learn through having them explained to you, but through doing them repeatedly yourself.

Implicit memory: People commonly refer to implicit memory in terms of television advertisements or product placement in TV shows, and this is actually a good example. Perhaps you are considering buying a new computer, and you have no particular reason for wanting a certain brand, but you find yourself believing it is the best. It is hard to say for sure, as many factors could be at work, but perhaps you are a big fan of a tv show where they all use that brand of computer. It may not be a major part of the show, but you begin to associate that brand of computer with the show which you love, and presumably, you would then also associate it with the characters who you are fond of. A related example comes from my boyfriend, who occasionally uses very random phrases. He generally isn’t sure where they came from until we are watching a movie or tv show when he hears a character use the phrase and suddenly realises that is where he must have heard it. In other words, he doesn’t consciously remember hearing it in a particular context, but he has picked up the phrase.

A declarative memory is one which you are consciously aware of, or in other words, a memory which you could articulate if someone asked about it. There are at least two types of declarative memory: episodic and semantic.

Episodic memory is your memory of events which have happened in your life. For example, memories of what you did on a family trip many years ago, memories of events (e.g., birthday parties) from your childhood, memories of what you had for dinner last night or what you watched on tv. We don’t remember every event that occurs in our lives, but we do remember a lot of things which we have done, seen, or experienced.

Semantic memory is like the distillation of all of the experiences you have. Instead of being about exactly what happened at your seventh birthday party (which would be an episodic memory), a semantic memory is about understanding what a birthday party is. For example, semantic knowledge would include the fact that there is almost always cake or a treat of some sort, often with candles for the birthday person to blow out, there is probably a time for everyone to sing ‘Happy Birthday’, there may or may not be balloons, signs, decorations, and gifts, there are probably cards, there may be games, etc. Another example of semantic knowledge would be understanding what an orange is – the color, the taste, the size, shape, the different ways it can be cut, eaten, juiced, where they grow, and what else is related (e.g., a pineapple is another fruit, but it is quite different in taste, color, and the way it is cut up/eaten, whereas a tangerine is not quite the same as an orange, but it is very similar).

These forms of memory are all related to one another, but I will save talking about the interaction between these forms of memory for a different post. In the meantime, I hope everyone out there in the blogosphere has had a nice weekend. I am excited because on Sunday evenings, there is American Football (NFL) on tv in the UK, so I get a little taste of home each week in the fall. By the way, I just noticed that I used the word fall (rather than the UK word – autumn) because I am talking about something from back home. Funny, isn’t it?! Anyway, enough of my tangent. I am off to heat up some leftover tomato walnut basil pasta, which is one of my favourites from Angela‘s amazing vegan blog. I make big batches of this pasta sauce and freeze it for easy meals when I don’t feel like cooking.

Please note: I did not use any particular references for the above information, other than double checking my own memory from my undergraduate cognitive psychology textbook: Goldstein, E.B. (2005). Cognitive psychology: connecting mind, research, and everyday experience. Belmont, CA, USA: Thomson/Wadsworth.

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