"When I am talking with people I keep getting anxious that I will forget their names, or I will forget something simple like my own telephone number and give them wrong information. All my life I have thought of older people as having poor memory and now its my turn to lose it."

Joan, 78 years old

Whenever I am talking with seniors, one of the issues that is very likely to come up is memory, and the idea that older people inevitably suffer a big loss of memory. One of the widely accepted stereotypes about seniors is that they have poor memory and thinking ability, and this seems to be true at least in most Western societies (in some traditional Eastern societies the stereotype of older people is rather different. Seniors are assumed to know a lot more, be wiser, and generally to be better thinkers).
What exactly is memory? What are the different kinds of memory? By addressing these questions, we can move toward a better understanding of aging and memory.

What is Memory?

In everyday language when we ask a question such as, "Can you remember the house number?" We are typically referring to only one aspect of memory: retrieval. But in scientific research the term memory refers to more than this. Traditionally, researchers distinguished between at least three activities involved in memory. First, the encoding or "taking in" of information. Second, the storage of information. Third, the retrieval or "recall" act. Correctly remembering a bit of information, such as a house number, requires that we get all three activities right. If one of these goes wrong, then we will not "remember" correctly. For example, you probably have experienced the frustrating feeling that you "know" something (such as a house number), in the sense that you are sure you took in that information and stored it "somewhere in your mind," but are now unable to retrieve it. This kind of problem often arises because the information was stored in a way that does not allow for easy access (in the next discussion I am going to review some ways of improving one's storage strategies).

What are the different kinds of memory?

In the late nineteenth century, Hermann Ebbinghaus began systematic research on memory, using himself as the subject. He created over twenty-two hundred nonsense syllables (such as "zup" and "ved") which served as the bits of information to be memorized. Ebbinghaus discovered that short term memory, which covers a time span of up to about twenty seconds, has a limited capacity of around six or seven bits of information. This finding was later elaborated by modern researchers, leading to a famous dictum that short term memory capacity is seven plus or minus two, meaning that most people will remember between five to nine bits of information in the short term. Early research led to the idea that some bits of information pass through short-term memory and end up in long term memory, which can span months or years. If a list is presented, items at the beginning of the list and the end of the list are more likely to be remembered more than items in the middle. This recency effect and latency effect suggests that important items should be placed at the start and the end of any list to be learned.
Other types of memory identified include iconic memory, which is like a split second image and fades quickly (rather as a negative might face under light); and flashbulb memory, which is a vivid memory associated with an emotionally powerful event (for example, for many people alive in the 1960s, the assassination of president Kennedy serves as a flashbulb memory). More recently, a lot of importance has been given to working memory: simply put, this is memory we are "working on" at any one moment. Short term memory is now seen as a part of working memory.
Another very important distinction in types of memory is that between explicit and implicit memory. Explicit memory involves awareness: We know that we remember something when we remember it (Jane explains to Samantha how to use the calculator). Implicit memory lacks awareness: we remember something but are not aware of remembering (Jane is unable to explain how to use the calculator and thinks she has forgotten, but finds that she can use it when she holds it in her hands). Implicit memory often involves skills: things we find we can do, even though we are not aware of how.
The different types of memory are very important for our discussion, because aging does not have the same relationship with all the different types of memory. As we shall see in the next discussion, seniors maintain performance level of some types of memory activity all of their lives. Healthy seniors are also able to perform as well as younger people on some important memory tasks, by compensating for "hardware" losses. In collaborative memory tasks, where people remember things through discussions with partners, seniors can in some respects actually perform better than younger people. So the picture is not one all bad.