Types of Memory

I divide memory into three parts – short-term, long-term and working memory. Other existing memory models consider short-term and working memory to be the same mechanism. I make a distinction between the two. Working memory, as the name implies, is the information we work with directly while performing various cognitive tasks. The information is taken from both short-term and long-term memory to be able to process information, store it and make it available for future use.

Short-term memory, on the other hand, contains mainly new data which we take in through our senses. Another term for this type of memory is “sensory memory.” Normally, we only keep data in our working memory for a short while from a few seconds up to a minute. Afterwards, the information is stored in long-term memory. The process of storing and retrieving information from working memory to long term memory can repeat itself many times while doing more complicated cognitive processes.

When we learn how to operate new machines, new software programs, or any new information for that matter, we use our working memory function in order to understand what principles and procedures the particular tasks involve. The learning process is based on our previous abilities, which we retrieve from the long-term memory, and from information that we collect through our short-term memory. This information is processed in our working memory, which acts as the working board where we combine previous data with new information based on direct input from the senses. With repetition and practice (when skills are involved), all this information is solidly stored in our long-term memory banks for future reference and retrieval: either for repeat usage or for the purpose of using it to help in learning similar or even more complicated material.

Working memory interacts not only with sensory memory and long term memory, but also with parts of the brain related to attention, learning and executive functions such as decision making and prioritizing (located at the pre-frontal lobes).

For those who have a basic understanding of computers, the following may serve to better understand how working memory works.

Say you want to key in certain data, notes perhaps, into a computer file. The keyboard acts as the sensory input, equivalent to our short term memory, transferring all the raw information to what is called RAM memory. RAM acts in the same way as our working memory, in the sense that it holds the information we are working with. It also temporarily holds the different programs we are using. It is displayed on the screen to shows us the programs currently in use as well as the data we have keyed in (equivalent to sensory or short-term memory), and it enables us to perform different functions in real time. Once we store the information on the hard drive, which in this example represents long-term memory, the information can then be later retrieved for further use.

Working Memory Capacity

Our working memory is limited to a few distinct information units. Titled “digit span,” it reflects how many digits, or chunks of data, we can contain at one time. This capacity is typically between 5 and 9 units, with an average of 7. The term: “the magical number seven, plus minus two” was coined in 1956 by psychologist George Miller, who studied memory extensively. This number, also represents the amount of what I call “channels of attention,” which refers to the amount of tasks we can do consciously – or which we can focus on at any given moment. This is the reason, by the way, why our telephone numbers consist of seven digits. Seven is the optimal number of digits which our working memory can process. When working memory is bombarded with too much information, it goes into overload mode and fails to transfer important data to long-term memory, and as a result some of the information may get lost.

Aging, stress, disease or injuries tend to narrow the channels of attention, so that instead of working with seven channels, only five, four, sometimes even less remain available. This diminished capacity would also explain why we cannot concentrate well when we are tired, in pain, or preoccupied with worry and stress; these conditions simply occupy some of the channels, leaving between one and three available channels with which the mind has to process information.

The availability of fewer “channels” may be enough for a very simple task, such as turning on the TV, yet be insufficient to perform a more complex task for instance, following an educational program on TV, or reading an article in a magazine. In addition to an inability to concentrate normally, the ability to retain information decreases dramatically as well. Have you ever tried to read at the same time as someone was talking to you? You can probably do a little of both, but you would not perform either role as well as if you were to give your full attention to only one task. People who are able to do this well are those who have eight or nine channels available to them. How we allocate the various channels thus determines what we pay attention to, as well as how attentive and focused we are.

Working Memory and ADHD

Individuals suffering from ADHD or LD (learning disabilities) suffer among other things from impaired working memory, which is one of the reasons why they have problems processing information properly. It also explains why they have problems understanding concepts or why it many times, takes them longer to understand complicated concept – math for example. Their working memory is not big enough to see the picture in its entirety.

We have developed in our clinic, specific programs to train the brain to enhance not only working memory, but also many other core cognitive skills such as visual processing, auditory processing, attentional flexibility, inhibition control, multitasking divided attention and a lot more. The complete list can be viewed here.