States of Memory

The amygdala is responsible for our emotional perceptions of events. This is important to memory because it associates cues with consequences. When we remember how we felt when something in the past happened, the amygdala is at work. It is also used for the consolidation of long term memory. Researchers have found that the level of emotional arousal a person has when learning something affects its strength in long term memory. The more emotional arousal a person has, the stronger the memory will be.

Short Term Memory
Short term memory allows a person to recall something after a short period of time without practicing or rehearsing. George Miller wrote a paper on short term memory called “The magical number 7 +/- 2.” He concluded from his experiments that we could retain 5 to 9 items with our short term memory without rehearsal. The amount can be increased if items are “chunked” together. Most people remember phone numbers in three chunked sets, the area code, the first three numbers, and the last four numbers. After a short period of time, this information degrades and becomes lost unless it is repeated or rehearsed.

Long Term Memory
Long term memory refers to retention of information over the long term from days to years. There are 2 types of long term memory, declarative and procedural. Declarative memory concerns historical events and knowledge of the external world. Procedural memory concerns remembering how to use objects and moving our body. For example, riding a bike would be considered a procedural memory. Remembering something that happened as a child would be declarative memory. Another difference between these two types of long term memory is procedural memory does not require conscious recall, while declarative memory does.

Long term memory is stored in many different places in the brain. Some theorists even believe some memories are stored elsewhere in the body such as the heart. When memory is stored, it tends to cluster together like the librarian in our example categorizes books. Information is connected together to related subjects that are meaningful and relevant to each other. The ways information becomes connected is unique to each person and the experiences they have had. For instance, coconuts remind me of my family. These two subjects may seem unrelated so let’s track my thoughts to see how they are connected. If I think about coconuts, I see what the coconut looks like on the outside and inside, I know where it is grown, and I remember what it tastes like. As I remember this information, I think of coconut crème pie. Coconut crème pie is my favorite. Then I remember eating it on my birthday with my family because I don’t like cake. This memory in turn brings up other information about my family, and so on.

Simple connectivities with memory from current people:

Atkinson and Shiffrin
Richard Atkinson and Richard Shiffrin were psychologists who collaborated to formulate their own model of memory. Their theory (the Atkinson-Shiffrin model) proposed that memory consisted of 3 stages; sensory memory, short term memory, and long term memory. They believed that first, we take in information through our senses (sensory memory). The information is retained for a matter of seconds before it degrades and disappears. If, however, this information is rehearsed or repeated, it is transferred to short term memory. The length of time information can remain in short term memory varies from person to person. If the information is repeated, it will stay in short term memory longer before it degrades and disappears. If the information is rehearsed enough times, it is transferred to long term memory.

Alan Baddeley and Graham Hitch
Baddeley and Hitch collaborated to propose a memory theory called the model of working memory. They described the concept of working memory as having 4 parts; central executive, phonological loop, visuo-spatial sketchpad, and episodic buffer. The phonological loop, also called an articulation loop, consists of auditory memory traces that degrade quickly. In simpler words, if we hear something, we will forget it quickly unless we rehearse or repeat what we have heard. Rehearsing refreshes the memory traces before it disappears.

The visuo-spatial sketchpad is like the phonological loop except it concerns things we see. The episodic buffer connects spatial, visual, and verbal information in chronological order. This allows us to remember pieces of a storyline in the correct order. The central executive controls all these components. It allows us to change from storing information to retrieving information or switching between tasks. It binds information together in meaningful ways, allows selective attention, and inhibits other thoughts or behaviors when needed. Another way of thinking about working memory is that we use working memory to manipulate information while we learn and complete tasks. The retention of working memory is longer than short term memory and through working memory, we decide what information needs to be transferred to long term memory.