The first hundred years or so of psychology have unraveled many of the mysteries of memory. Memory Memory is no longer perceived as a single brain function but rather as a set of distinct faculties that have different uses and operate over different time scales. A memory can last for anything from a fraction of a second to most of a lifetime.
Studies of how memory skills are lost or retained when the brain is damaged have helped scientists to identify the different areas of the brain involved in different kinds of memory. Recently, imaging techniques have shown remembering in action, revealing memories as enduring patterns of brain activity that re-create experiences.
Only humans seem to have a certain kind of memory: the ability to call up and reflect on previous experiences. This ability may have played a major part in our evolution – and continues to fascinate us in the present day.
Working Memory: The Mind’s Blackboard:
In our everyday lives, we constantly need to remember little pieces of information – phone numbers, lists of names, a round of drinks – for just a few seconds. This type of temporary memory is known as short-term or ‘working’ memory.
Working memory is the mind mechanism that allows you to hold numbers in your head when you are doing mental arithmetic and provides somewhere for you to sketch mental maps when you are giving directions. In fact, you are using your working memory right now: as you read, your working memory holds the beginning of each sentence just long enough for you to reach the end. Without it, nothing you read would ever make sense. This type of memory is often described as the mind’s blackboard – like a real blackboard, it provides a space to jot down information needed for the task in hand, and it is ‘wiped clean’ when you start a new cask.
The concept of working memory grew out of the older idea that we have two main types of memory: long-term memory, which stores events, facts, and knowledge for anything from a few hours to many years, and short-term memory, which holds information for a matter of moments. Psychologists realized that short-term memory is in constant use as we talk, think, and act, so they began to use the term working memory to emphasize its active role.
The ‘magic number’ seven
Although working memory is crucial to our conscious thought processes, it holds surprisingly little. In 1956, US psychologist George Miller concluded that working memory can handle about seven pieces of separate information at once. Miller developed a formula – ‘seven plus or minus two ‘ – to show normal, working memory capacity. Seven items are the average capacity, with nine and five as the top and bottom of the normal range. Most of us can hold only seven items at the forefront of our minds.
So, if you are trying to remember a seven-item. Shopping list and then think of something else to add to the list; at least one of the original items is likely to be forgotten. If you are distracted briefly, you may forget the entire list. It is this tendency in working memory for new thoughts to push out old ones that sometimes causes us to forget what we were about to say in a sentence or arrive upstairs wondering what it was that we were on our way to fetch.
If you need to hold something such as a phone number in your short term memory for a few seconds, the easiest way to do it is to ‘ rehearse ‘ it- that is, repeat it over and over again, either out loud or inside your head. However, if you want to remember the number more permanently, you will need to think about the number and relate it to something you know so that it becomes lodged in your long-term memory store.
The sketchpad and the phonological loop
Two British psychologists, Alan Baddley, and Graham Hitch, first put forward the idea that working memory consists of so fatlease two ‘ mental blackboards’ – the phonological loop, which stores words and numbers briefly in auditory form, and the visuospatial sketchpad, which stores images temporarily. It is now known that the phonological loop and the sketchpad use different parts of the brain, which means that both can be used at the same time. This explains why people can normally navigate a car and hold a conversation at the same time. Navigating involves picturing a route and so uses the visuospatial sketchpad, while talking involves words and so uses the phonological loop. If, however, you try to carry out two tasks that both use the phonological loop – for example, reading a book while the television or radio is on – you will run into difficulties.
Sensory and iconic memory
The most temporary form of memory is known as sensory memory, which holds data from our eyes, ears, and other senses for just a split second. Our senses provide us with far more information than we can cope with, so we use sensory memory to hold information briefly while we pick out the important parts.
Sometimes, we mishear what someone says and are on the point of asking them to repeat it when we realize that we did hear it after all. This is sensory memory in action. As soon as we realize that we haven’t heard properly, we examine our sensory memory and find an exact ‘recording’ of what entered our ears.
The visual form of sensory memory is called iconic memory. This holds onto visual information taken in a fraction of a second ago. It is this that enables us to make light pictures form in front of our eyes using sparklers and to see separate images on film as continuous action.
