Memory

Memory

1. Capacity refers to the volume of information/data stored in a memory store at any given time.

   • Sensory memory consists of sensory information retained in an unprocessed form in the sensory system through which it entered. This form of memory is short-lived (0.5-3 seconds) but has a large capacity.
   • The capacity of STM is thought to be 7+/-2. This is based on Miller's idea that many things come in groups of 7, suggesting that we are predisposed to remeebring this quantity and that a 'chunking' method can help us recall more information.
     • Jacobs also demonstrated that the mean letter span was 7.3 and the mean digit span was 9.3. Procedure: Researcher reads four digits and increases until the participant cannot recall the order correctly. Final number=digit span. Findings: On average, participants could repeat back 9.3 numbers and 7.3 letters in the correct orfer immediatly after they were presented.
   • The capacity of the LTM is unlimited.

2. Duration refers to how long information can be stored in each memory store.

   • Sensory memory is a very short-term memory store for information being processed by the sense organs. Sensory memory has a limited duration to store information, typically 0-3 seconds.
   • The duration of STM is 18-30 seconds, as demonstrated by Peterson et al, who found that increasing retention intervals decreased the accuracy of recall of consonant syllables in 24 undergraduates, when counting down from a 3 digit number.
     • Procedure: 24 students were given a consonant syllable to recall and a 3-digit number to count backwards from. The retention interval was varied: 3,6,9,12,15 or 18 seconds. Findings: After 3 seconds, average recall was about 80%. After 18 seconds it was about 3%. STM duration without rehearsal is up to 18 seconds.
       • One limitation of Peterson et al.'s study is that the stimulus material was artificial. This is not completely irrelevant as we do soemtimes try to remember fairly meaningless material. Even so, recalling consonant syllables does not reflect most everyday activities where what we are trying to remember is meaningful. This means the study lacked ecological validity.
   • The duration of LTM is unlimited, as shown by Bahrick et al, who found that photo recognition of graduating classmates of the 396 participants decreased from 90% to 70% between 15 years and 46 years of graduating .
     • Procedure: Participants were 392 Americans aged between 17 and 74. Recognition test - 50 photos from high school yearbooks. Free recall test - Participants listed names of their graduating class. Findings: Recognition test - 90% accurate after 15 years, 70% after 48 years. Free recall test - 60% recall after 15 years, 30% after 48 years.
       • One strength of Bahricks' study is that it has high ecological validity. This is because the researchers investigated meaningful memories. When studies on LTM were conducted with meaningless pictures to be remembered, recall rates were lower. This suggests that Bahricks et al finsings reflect a more 'real' estimate of the duration of LTM.

3. Coding refers to the format or type of information stored in each memory store. Can be stored Acoustically (sound) or Semantically (meaning).

   • Baddeley demonstrated the different coding in STM and LTM in his experiment where he found that more mistakes were made by participants when recalling acoustically similar words straight after learning the (STM recall) whilst more mistakes were made when recalling semantically similar words 20 minutes after learning them.
     • Procedure: Acoustically similar or dissimilar words. Semantically similar or dissimilar words. Findings: Immediate recall worse with acoustically similar words, STM is acoustic. Recall after 20 minutes worse with semantically similar words, LTM is semantic.
       • One limitation of Baddeley's study was that it used artificial stimuli rather than meaningful material. For example, the word lists had no meaning to the participants, so Baddeley's findings may not tell us much about coding in different kinds of memory tasks, especially in everyday life. When processing more meaningful information, people may use semantic processing even for STM tasks. This suggests that the findings from this study have limited application.

4. The Multi-store model was developed by Atkinson and Shiffrin and includes three separate unitary stores. The MSM suggests that information flows through three separate stores in a FIXED linear and each store has different roles in the memory process.

   • The sensory register gathers information from our sense organs, and each sense is coded differently. If we pay ATTENTION to sensory information, then it will pass to STM. Forgetting occurs due to rapid decay if no attention is given to it.
   • Short-term memory has a limited capacity of 5 - 9 items, and a limited duration of up to 30 seconds. Maintenance Rehearsal allows information to be held in the STM. Elaborative rehearsal transfers information from STM to LTM by processing the information semantically. Forgetting occurs from STM due to Displacement and Decay.
   • Long-term memory has an unlimited capacity and a duration of a few minutes to a lifetime. Forgetting seems to occur because of interference and retrieval failure.
   • Evidence to support the distinction between STM and LTM includes clinical studies of patients with Korsakoff's syndrome. Korsakoff's syndrome occurs in chronic alcoholics and severely damages the brain. There is little effect on STM, but LTM is severely impaired. For example, you can converse with a Korskroffs patient, but because of their impaired LTM, they will not remember the conversation. This supports the idea that STM and LTM are seperate unitary stores.
   • Further clinical evidence comes from case studies, for example, KF suffered brain damage as a result of a motorcycle accident; it had no effect on the LTM but led to poor performance on many STM tasks, thus suggesting that STM and LTM are completely separate stores in memory. Cases such as these support the MSM in that they point out a clear distinction between LTM and STM, that each store is separate.
   • Cohen and Squire suggested that LTM can be divided into declarative memory and procedural memory. For example, Clive wearingwho contracted a viral infection causing extensive brain damage, had lost his declarative memory, but still had use of his procedural memory. This is evidence to suggest that the two separate systems of declarative memory and procedural memory exist in LTM, therefore undermining the MSM as it is far too simplistic.