Three differences between long term memory and short-term memory are capacity, duration and encoding. Capacity in short term memory is 9 items and duration is 20 seconds if information is not rehearsed. However, both of these in long-term memory are unlimited. Encoding in short term memory is mostly acoustic, that is, we store information as sounds by repeating it over and over to ourselves verbally. Encoding in long-term memory is mainly semantic. This is when we remember information because of the meaning of it.
We can also use other codes such as visual, taste, acoustic and smell in long term memory.
George Miller investigated the capacity of short-term memory by using the digit-span technique. He read participants a list of numbers, ranging from four numbers in a set, to ten numbers in a set. He then told participants to write the numbers down after he had finished reading out each set. Miller found that the average person remembered 7 numbers, but maybe two less or two more on occasions.
In conclusion, Miller discovered that a normal humans short-term memory capacity is very limited compared to long-term memory.
Sigmund Freud first introduced repression in 1895. It is a form of induced forgetting, where traumatic and distressing memories that could threaten a person’s well being are pushed out or repressed from conscious memory to unconscious memory. Williams and Zimbardo support the idea of repression. They both carried out research on women. Williams examined hospital records of young girls who had been sexually abused. Seventeen years later, the women were tracked down and questioned.
38% of these women had no conscious memory for the events in which they were treated, yet many of these women could remember later incidents of sexual abuse.
Zimbardo studied a woman named Eileen. When Eileen was eight years old, her friend Susan disappeared. 20 years later, Eileen realised her daughter looked just like Susan, and the repressed memory was retrieved. Her own father had sexually abused Susan and beaten her to death with a rock in front of Eileen. She was threatened that if she told anyone her father would kill her too. Her father was later found guilty of murder and sentenced to life imprisonment.
A criticism of the theory of repression is that the memories are not easy to retrieve. Even if they were, recreating repressed memories in laboratory conditions is extremely difficult and it would be exceedingly unethical to subject participants to the stress of reliving such situations. If the memory was repressed, it was obviously so terrifying the person chose to purposefully forget it so bringing the memory back in to conscious mind would be highly unorthodox.
There are several other explanations in the factor of forgetting. One of these is trace decay theory. This happens in short-term memory. It assumes that memories leave a trace in the brain. The trace is some form of physical and/or chemical change in the nervous system. Forgetting occurs as the trace decays or fades, both of which occur rapidly. Another explanation is displacement. This is where information is pushed out of the memory to make way for new information. This explanation only focuses on short-term memory however. The two main explanations of forgetting in long-term memory are interference and retrieval failure. Interference can be proactive where old memories disrupt new memories, or retroactive, where new memories disrupt old memories. Evidence suggests the more similar the two or more pieces of information, the more likely it is that interference will occur.
There are several different types of retrieval failure. One of these is called the tip of the tongue effect. It occurs when people know they know something but are unable to recall it. We can recall similar sounding words or words that have the same meaning but not the exact word we want. The other two types of retrieval failure occur because of encoding. The first type has to do with the physical/psychological state you are in when the information is being encoded into long-term memory. If you are in a happy mood it is more likely you will remember something you did whilst happy if you get into the same state of mind again. Also, when you are happy you tend not to remember anything sad that has happened but all the good things that have happened that have made you smile stick out in your mind.
The second type of retrieval has to do with the place you are in when you encode the information. It has been found that encoding in one environment and retrieving the information in another is les effective than encoding and retrieval in the same environment. This has to do with things in your surroundings you look at whilst you are encoding something and when you look at these things again you are more likely to remember them. This is also known as using cues to help retrieve information.