Every one has memory problems or loss of memory now and then. But what is memory? Memory is the most fundamental of human cognition, without it we could only act on instinct and have automatic, stereotyped reactions to our ever changing environment. Indeed, because memory is so important we should know more about it so we can take care of it.
Memory can be divided roughly in two forms: long term memory (LTM) and working memory (WM). Long term memory has a lot to do with holding the information for a time longer than say one day, although science really does not have set a clear time boundary. It usually considers everything longer than a minute as 'long term'. It has two fundamental processes: consolidation and restoration. The consolidation process is actually what we all think of as ‘memory’: storing things we do and experience in a long term store. This storing already begins when something is in our working memory. However, the time and amount of processing determines how good we can store this information. There are other factors involved but I will tell them later on the pages about memory training. The second process is the retrieval or ‘restoration’ process. Out of what we actually stored in our LTM we have to find it and reconstruct this memory again. Unlike a hard drive of a computer, we do not store everything in full detail. Parts of an image or story are stored and we must find and retrieve those parts and put them back together into a memory of an image or story again. Every retrieval attempt is not 100% so it actually changes our stored image. You could say that when remembering things repeatedly we alter the stored image. That’s the reason that it is possible to remember something that actually didn’t happen that way. Our memory is fallible!
The other form is working memory, formerly known as Short Term Memory: common sense tells you that this is information just recently stored. Because science has a much shorter time frame for this working memory (maximally 60 seconds) than the public, I will consider everything that has to remembered for a period longer than 60 seconds as your long-term memory. Most memory problems or complaints concern this long-term memory. Beneath you will find a graphic explaining these forms of memory:
On my page about Attention: what is it? I will tell you more about the interaction and overlap between attention and working memory. Actually, I will state that attention IS working memory.
Further important subdivisions in memory are more personal memory (technically called episodic memory) and more abstract memory (called:semantic memory). In fact, this is somewhat academic because all memory starts out with being personal since everything we start to remember begins with experiences which are very personal, related to a specific surrounding, time and place. An example is when we learn what a bicycle is. Perhaps you can remember your first time bike as a very personal experience. Over time, you have had many experiences with bicycles and in this way the understanding of 'bike' became more and more an abstract fact (decoupled from any specific experience or memory). 'Bike' now has become a part of your semantic (meaning) memory.
Another main difference in memory types in science is explicit and implicit memory. The difference lies in how conscious we are of whát has been stored in our memory banks. Usually, motor actions like a tennis serve or riding a bike are stored automatically: we have not much of an idea how exactly we have stored this in our memory. But we do know that after some practice we have actually learned to play tennis or ride a bike.
Now that we know the main memory types (as far as science is concerned), let me focus on at least two common misconceptions about our memory. The first is that we can store everything perfectly, just like a hard disk of a computer. The second is that our memory is unlimited. The first truth is that our intake and storage system is not perfect: we differ as humans in the amount of information we can take in or process. That has a lot to do with our limited attentional capacities. But also we are very selective when it comes to whát information we will store for the longer term. That depends largely on what we already know (i.e. have stored in our memory banks) and on our interests. Interesting things will always be remembered more easily and firmly than boring things. This fact has to do with our 'coloring' capacity when we process information: by this, I mean our capacity to add emotional color to the information we receive. Every bit of information we process, be it some words, sounds, smells or views, is stored together with our emotional mood at that very moment. Being so limited in our attention and so selective in taking up information, estimates vary in how much we can remember. For example, in a conversation with a doctor, only 10 to 25% is remembered well! Seeing a news item on television is even worse: less than 10% is remembered correctly after a couple of hours.
So what is a normal memory when we tend to forget the large majority of the information we perceive? Well, neuropsychology (the science of the relationship between brain and behavior) only considers an information process such as memory as abnormal whenever it is seriously different than in similar other human beings. Again, 'hard science' such as MRI or CT-scans can tell us nothing about how serious our brain dysfunctions are when it comes to memory problems. Only (neuro)psychological tests can tell. On another page about neuropsychological tests, I will delve deeper into test psychology and how these memory tests look like. For now, you have to remember that neuropsychology has a pretty good idea of what is abnormal in memory functioning and it concludes so with the help of a database of test performances of 'normal' people similar to you.
In surveys and studies people complain the most about their ability to remember people's names and in relation to that, their faces. Not so amazing because we deal a lot with other people in our daily lives and therefore we come across a lot of new names which would be nice to remember. It is quite social and handy to remember the names of people you meet. Another memory complaint is forgetting important numbers or codes such as a telephone number or your codes of your credit card or your password of the computer at work. The third memory complaint often heard is forgetting what you've read, especially when it is important. Other memory problems are forgetting what we were doing, forgetting where we have put something at home, and forgetting the things we had to do today. Because these last problems are very closely related to attention problems you should read my pages about Attention problems and what attention is.
Because everyone has such complaints ánd can give a personal example of one of those memory problems, it seems that this is quite normal, common. Well yes, it is. One of the problems of a neuropsychologist is that the number of complaints about cognition, including memory, does not tell much about how your memory really is different from that of other similar people. One of the reasons is the large variability of memory capacity in normal human beings. Some have an astonishingly sharp and large memory, others barely seem to remember the birthday of their children (especially men). So, when forgetting names of people, things to do and phone numbers is quite common, when should you worry about your memory?
Just as with attentional problems, I told you that a sudden drop in your memory capacity is not really a good sign. Normally, this does not happen that quickly. But say, after a blow to your head in your favorite sport like horseback riding or soccer, you can experience memory problems which you hadn't had before. Usually, such sudden memory problems are quite obviously related to such a serious incident where your head was somehow injured. Most of the time however, memory problems seem to develop slowly, barely noticeable to yourself. Indeed, it is quite normal that others such as your friend or partner notice your memory problem earlier than you do. A brain dysfunction does not hurt, normally. Signs are that you tend to ask the same questions several times a day and your partner gets irritated. Another sign is that you forget more than once everyday where you have put things. Because of the high frequency of such behavior it is quite a sensitive sign or indication for a memory that is changing. Of course, an examination would suffice extremely well as a memory test but we tend not to do many examinations once we quit high school. Another serious sign is whenever we forget, again several times a day, what we were doing. Our brain is constantly monitoring and storing our actions. Whenever we forget our actions in a short time span, in one day, something can be wrong with this automatic storing device in our brain.
Memory can be divided in two forms: working memory and long term memory. Three memory processes are of interest to scientists and clinicians: the intake process (actually attending to and processing the to be stored information), the storage process (consolidation) and the restoration (retrieval) process in which stored information is retrieved from long term storage. There can be problems in all three stages of memory processes, leading to the most common memory complaints in daily life.
As with deficits of attention, memory problems starting suddenly after a blow to your head or after any other clear brain injury, are mostly pretty obvious. A sudden increase in forgetfulness, especially in frequent daily life tasks, is a common result. It becomes more difficult when memory loss is more gradually developing, for example over a period of several months. Forgetting things quite frequently every day may be a sign of trouble. On another page on this website I will explain in more detail what can be considered examples of normal forgetfulness in daily life. On a page where I explain the effects of brain injury in daily life, examples will be given of really serious memory disorders. Finally, when you are interested in hów a memory disorder is detected by a neuropsychologist, I suggest you follow this link to learn more about memory tests.