Memory (pmt)

• Coding refers to the format or ‘type’ of information which is stored in each memory store.
• Capacity in memory refers to the volume of information/data that can be kept in any memory store at any one time
• Short-Term Memory (STM) is thought to have a capacity of 7 +/- 2 items, according to Miller
• Long-Term Memory (LTM) is believed to have an unlimited capacity
• Miller's idea is that things come in groups of 7, which suggests we are predisposed to remembering this quantity and that 'chunking' can help us recall information
• Jacobs demonstrated that the mean letter span was 7.3 and the mean digit span was 9.3, indicating the number of letters or digits we can recall after increasing intervals
• • Duration refers to the amount of time that information can be stored in each memory store.
• A key issue with historical psychological research, particularly concerning Jacobs, is the lack of standardisation and appreciation of scientific methods. For example, the current laboratory experiment methodology produces highly reliable and valid data through controlling and so removing the effects of extraneous and confounding variables. The same is unlikely to be said of Jacobs, where confounding variables such as a noisy room or difficult word lists, may have had a greater influence on accuracy of recall, leading to unreliable results.
• A particular strength of Bahrick et al’s 1975 study is the use of meaningful stimuli, and a methodology which is high in mundane realism. This suggests that the findings have high ecological validity because they can be easily generalised to real-life, due to the stimuli reflecting those which we would often try to learn and recall in our day to day lives: information with personal and meaningful value!
• Conversely, the key issues with the Petersen et al and Miller et al studies is that they feature methodologies with low mundane realism, thus producing findings with little ecological validity. This is due to the use of artificial stimuli which has little personal meaning to the participants, and so does not accurately reflect everyday learning experiences. This therefore limits the generalisability of such findings
• More recent research has suggested that Miller may have over-exaggerated the capacity of STM, and that the capacity is more similar to 4 chunks as opposed to the original 5-9 limit. This may reflect the outdated methodologies adopted by Miller and specifically, the lack of control over confounding variables which may have contributed to this inaccurate estimate.
• The multi-store memory model (MSM) represents how memory is stored, transferred between the different stores, retrieved and forgotten.
• There are 3 stores: the sensory register, shortterm memory and long-term memory.
• The sensory register contains one sub-store for each of the 5 senses e.g. an echoic store for auditory information. Since it receives information for our senses, the sensory register has a huge capacity, but a duration of less than half a second.
• Therefore, information will only pass from the sensory register to the short-term memory store if we pay attention to it.
• STM is described as being acoustically encoded (Baddeley), having a capacity of 7+/- 2 items (Miller) and a duration of 18-30 seconds (Petersen). Maintenance rehearsal occurs when we repeat the new information to ourselves, allowing the information to be kept in the STM. Prolonged maintenance rehearsal allows the information to pass into the LTM, whilst a lack of such rehearsal causes forgetting.
• LTM is described as being semantically encoded, having an unlimited capacity and a very long duration (over 46 years, as shown by Bahrick et al). In order to remember information, ‘retrieval’ must occur, which is when information is transferred back into the STM, and will continue to pass through the maintenance loop afterwards.
• There are different types of LTM, as proposed by Tulving et al i.e. procedural, semantic and episodic.
• The MSM suggests that the amount of maintenance rehearsal determines the likelihood that the information will pass into the LTM, whereas Craik and Watkins (1973) suggest that it is the type of rehearsal which is more important. They suggest that elaborative rehearsal, instead of prolonged rehearsal, is needed to transfer information from the STM into the LTM, by making links with existing knowledge.
• The MSM acknowledges the qualitative differences between STM and LTM by representing them as separate stores. For example, STM is encoded acoustically, whilst LTM is encoded semantically and has a much longer duration. Therefore, the MSM portrays an accurate view of the differences between the two types of memory, as supported by Baddeley and Miller.
• The MSM incorrectly represents STM as a single, unitary store. For example, Shallice and Warrington found that their amnesiac patient KF had poor STM recall for auditory stimuli, but increasingly accurate recall for visual stimuli. This, alongside KF being able to differentiate and recall both verbal and non-verbal sounds, suggests that there may be multiple types of STM.
• • There are 3 types of long-term memory: episodic, semantic and procedural.
• Episodic memory describes those memories which have some kind of personal meaning to us, alongside details as to when and how these events occurred, as well as the associated people and places. An example would be the memory of a wedding or the first time meeting a partner
• • Semantic memories describe our memories of the world and the associated knowledge e.g. an understanding of what words, themes and concepts mean. An example would be the ability to use information related to one concept to help us understand another.
• Procedural memories describe our memories of ‘learned skills’, such as swimming or driving.
• Episodic and semantic memories must be recalled consciously, whereas procedural memories are recalled unconsciously.
• Petersen et al. demonstrated that semantic memories were recalled from the left prefrontal cortex, whilst episodic memories were recalled from the right prefrontal cortex. This supports not only the idea that there are different types of LTM, but shows that they each have a different neurological basis because they are recalled from different parts of the brain.
• There is a practical application in being able to differentiate between different types of LTM. For example, Belleville et al notes that mild cognitive impairments most commonly affect episodic memories and so an increased understanding of episodic memory, alongside the differences between different types of LTM, may lead to improved, increasingly targeted treatments for mild cognitive impairments.
• Cohen and Squire drew a distinction between declarative and non-declarative memories. Declarative memories must be recalled consciously (i.e. episodic and semantic), whilst nondeclarative memories may be recalled unconsciously (i.e. procedural). However, this is a different classification and organisation system as the one used by Tulving, suggesting that his depiction of LTM is not entirely accurate.
• • The cases of HM and Clive Wearing show how one type of LTM may be impaired (episodic in their cases), but the other types of LTM will be unaffected (i.e. procedural and semantic).
• The WMM suggests that STM is made up of the central executive, the phonological loop, the visuospatial sketchpad and the episodic buffer
• • The central executive has been described as an ‘attentional process’ with a very limited processing capacity, and whose role is to allocate tasks to the 3 slave systems
• • The phonological loop processes auditory information and allows for maintenance rehearsal by being made up of the articulatory process (stores the words you hear) and the phonological store.
• The visuo-spatial sketchpad combines the visual and spatial information processed by other stores, giving us a ‘complete picture’ e.g. when recalling the architecture of a famous landmark. The VSS us divided into the inner scribe and visual cache. The capacity of the VSS is around 4-5 chunks (Baddeley).
• The episodic buffer integrates all types of data processed by the other stores (e.g. auditory, visual, spatial) and so is described as the storage component of the central executive, as well as being crucial for linking STM to LTM.
• The central executive has not been precisely defined. For example, the term ‘process’ is vague, and the central executive may be made up of several sub-components or even be part of a larger component itself in working memory.
• + Shallice and Warrington’s study of KF provides support for the WMM because their findings show that KF had very poor STM recall for auditory stimuli, but increased STM recall for visual stimuli. This suggests that the components of memory which process auditory and visual stimuli are separate (as described in the WMM through the phonological loop and the visuo-spatial sketchpad).
• Studies of dual-task performance, where each participant must undertake a visual and verbal task simultaneously, shows decreased performance for such tasks and so supports the idea that the central executive has a very limited processing capacity (as predicted by the WMM) and that the slave systems are in competition with each other for these tasks and resources.
• Neuroscanning evidence, such as that provided by Braver et al, has demonstrated a positive correlation between an increasing cognitive load processed by the central executive (as marked by increasing task difficulty) and increasing levels of activation in the prefrontal cortex. This supports the idea that the central executive has the role of allocating tasks to slave systems and has a limited processing capacity, as reflected by the increased brain activation levels, thus suggesting that the WMM is accurate in its mechanism of the central executive
• • Interference occurs when the recall of one memory blocks the recall of another, causing forgetting or distorted perceptions of these memories. Interference can be retroactive (new memories block the recollection of old memories) or proactive (old memories block the recollection of new memories).