Encoding, Capacity and Duration
Encoding - The form in which information can be stored in STM and LTM.
- Not usually an automatic process, attention has to be paid.
- In traumatic experiences information may be automatically encoded but on the other hand our ability to encode may be reduced when in a state of panic.
- We remember information more easily if it fits our expectations.
- Main method of encoding for STM is acoustic. Main method for LTM is semantic
Capacity - The amount of information that can be held in memory
- Refers to amount of information that can be held in memory
- Capacity of STM is 7+/- 2 items
- Capacity of LTM is unlimited
Duration - The length of time information can be retained in memory
- 20 seconds without rehearsal for LTM and a lifetime for LTM
Investigation into the Capacity of Human Memory
- Investigated the capacity of STM
- found that STM can retain 7 plus or minus 2 items.
- Capacity of STM can be increased by 'chunking', i.e. grouping the information into similar chunks.
- He concluded that STM has a limited capacity that can be referred to as the 'Magical Seven plus or minus Two'.
Multi-store Model of Memory Outlined and Evaluated
Atkinson and Shiffrin - Proposed that memory has three distinct stores: sensory memory, STM and LTM.
- Information reaches sensory memory through the senses, for example vision and hearing
- When we pay attention to this memory it is temporarily stored in STM.
- If we rehearse this information sufficiently, for example, by repeating it again and again, the information is transferred to LTM.
- Information from STM can be lost through displacement and decay. Information in LTM cannot be lost but may be difficult to retrieve without a trigger or cue.
- + Studies tend to confirm that memory does have distinct stores. Baddeley demonstrated that STM prefers acoustic encoding whilst LTM prefers semantic
- - Research has shown that the multistore model is an over-simplification, LTM uses different types of memory
Working Memory Model Outlined and Evauluated
Baddeley and Hitch's WMM - See STM as being divided into four parts:
- the central executive, that controls the system, the articulatory loop, that stores acoustic information for a short time, the primary acoustic store, that holds and recieves auditory information and the visuospatial sketchpad that deals with visual and spacial inormation
- This model explains how individuals are able to perform two tasks simulataniously
- + Psychologists generally accept that STM comprises a number of different processing systems because it is a more realistic was of explaining how memory works in everday life.
- + Baddeley has shown that we are capable of doing dual tasks at the same time.
- + PET scans show four different areas of the brain are active during different processing tasks, corresponding witht the models components.
- - The model is limited because we know so little about the central executive and its function and its capacity has never been measured.
- - Doesn't explain changes in ability to process information that has occured as a result of practice or time.
- - May lack ecological validity as much evidence has come from lab experiments.
Research Into Eyewitness Testimony
Research has shown that information can be added to an event after the event itself, and this information can be recalled as part of the original memory. This is critical in eyewitness testimony where the witness may mix the new information with the original memory.
Misleading information and leading questions can affect peoples memory and direct them to give a particular interpretation of the event.
A leading question directs a person towards a particular response the questioner desires.
A misleading question leads a person towards a response which the questioner knows does not fit the facts.
Loftus and Eyewitness Testimony
Elizabeth Loftus - A leading researcher in the field of eyewitness testimony
- study. Participants shown a film of a car accident. Later asked questions on events but different words such as 'contacted', 'hit', 'collided' and 'smashed' were used in questions about the speed of the car.
- participants estimation of speed varied depending on which word was used.
- 'smashed' elicited highest estimation of speed.
- Misleading questions asked immediatly after an event can influence later recall. The way in which a question is asked can influence recall of an event. Obviously this could be crucial in a court case.
- Loftus also demonstrated not all memories are distorted, her study involving a red purse being stolen memory shows that memory of major facts is not easily misled.
- Almost all Loftus' conclusions are based on lab experiments. Do these conclusions hold true for real-life situations and real-life witnesses?
A Study of Eyewitness Testimony
Aim: Elizabeth Loftus aimed to investigate whether misleading information after an event can be recalled as part of the event
- 150 students shown a three minute film of a car driving in the countryside, followed by an accident. Afterwards students were questioned on the film. Half the students were asked misleading questions such as 'How fast was the car travelling when it passed the barn?' ( there was no barn in the film). One week later the students were questioned on the film again.
- The group who had been asked the leading questions were more likely to recall a barn in the film comparedto the group who had not been asked misleading questions. In other words the experimental group had built the 'barn' into the recall of their film'
- Loftus showed that information can be added to a memory after the event. it demonstrated that at least in a lab study that misleading and leading questions can influence later recall.