Memory Notes

Short and Long Term Memory  Capacity Jacobs found that the average span for digits was 9.3 items and 7.3 for letters. Miller reviewed this and concluded that the span of immediate memory was 7 +/- 2.  Evaluation  The Capacity of STM may be even more limited to about 4 chunks. Suggests that is not as extensive as first thought. Research on capacity for visual information found that 4 items was the limit.  The Size of the Chunk also matters. people have a shorter memory span for larger chunks e.g. 8 word phrases than smaller chunks.  The Capacity of STM is not the same for everyone. Recall increases with age. The age increase could be due to a gradual increase in brain capacity or that people may develop strategies to improve their memory span.   Duration  STM: Peterson and Peterson studied the duration of STM. Each pp was given a consonant syllable and a retention interval of 3, 9 or 18 seconds. On average found that they were correct 90% over 3 seconds. 20% over 9 seconds and 2% after 18 seconds.  LTM: Bahrick tested 400 people on racial recognition from a yearbook. Pp tested within 15 years of graduation are 90% accurate. after 48 years this was 70% accurate in cued recall.  Evaluation  The testing of STM was artificial. Had low ecological validity as it didn't represent everyday tasks in life.  STM results could be due to displacement. Reitman used auditory tones instead of numbers so displacement wouldn't occur and found that the duration of STM was longer. Suggests in Peterson and Peterson study forgetting was due to displacement not decay.    Coding  Baddeley found that pp had difficultly remembering acoustical similar words in STM but not LTM, whereas semantically similar words posed little problem for STM but led to muddled LTMs. This suggests that STM is encoded acoustically and LTM encoded semantically.  Evaluation  Baddeley may not have tested LTM as he only waited 20 minutes before asking for recall.  STM may not be exclusively acoustic as some experments have shown that visual codes are also used in STM.  LTM may not be exclusively semantic. Long-term recall was related to visual as well as semantic categories. 

Multi-Store Model of Memory  Sensory Register  The place where information is held at each of the senses . The capacity is large but most information receives no attention and so remains for only a brief duration.  Attention  When attention is focused on one of the sensory stores, the data is transferred to STM.  STM Information held in STM is for immediate use. It has a limited duration and will disappear quickly is not rehearsed. Information can also be displaced due to its limited capacity.  Maintenance Rehearsal  Repetition transfers information from the STM to the LTM.  LTM Potentially unlimited in duration and capacity.    Evaluation  Strengths  Supporting Evidence  Controlled lab studies on Capacity, Duration and coding support the existence of a separate short and long term store. Beardsley found that the prefrontal cortex was active in STM but not LTM> Squire found the hippocampus was active when the LTM was engaged. Case Studies  HM had brain damage caused by an operation to removed the hippocampus from his brain to reduce his epilepsy. His personality and intellect remained intact but he was unable to from new LTMs.  Limitations  Too Simple  MSM suggests that both STM and LTM are single stores. However, research doesn't support this. The WMM was developed to show that there are multiple stores in the STM.  Long-Term Memory can be more than Maintenance Rehearsal Craik and Lockhart suggested that memories are created by the processing done. The more deeply items are processed the better they are remembers. Deep processing means doing more complicated things with the item to be remembered rather than just repeating it. 

The Working Memory Model