Coding, Capacity, and Duration of Memory

Coding, Capacity, and Duration of Memory

• Coding is the format information is stored in each memory store.
• Short-term memory (STM) relies on acoustic coding; long-term memory (LTM) relies on semantic coding.
• Baddeley (1966) demonstrated that recalling acoustically similar words is harder immediately after learning, while recalling semantically similar words is harder after 20 minutes.
• Capacity is the amount of information that can be held in a memory store at once.
• STM is considered to hold 7 +/- 2 items (Miller).
• LTM has an unlimited capacity.
• Miller suggested we group things in 7s, which aids recall through chunking.
• Jacobs found the mean letter span was 7.3, and the mean digit span was 9.3 when recalling after increasing intervals.
• Duration is the length of time information remains in each memory store.
• STM lasts 18-30 seconds. Petersen et al (1959) found increasing retention intervals decreased recall accuracy of consonant syllables.
• LTM duration is unlimited. Bahrick et al (1975) found photo recognition of graduating classmates decreased from 90% to 70% between 15 and 46 years after graduating.
• Lack of standardization in historical research raises reliability concerns.
• Lab experiments produce reliable and valid data by controlling extraneous variables.
• Bahrick et al's 1975 study had high mundane realism and meaningful stimuli.
• Petersen et al and Miller et al studies may lack ecological validity due to the artificial nature of stimuli.
• STM capacity may be closer to 4 chunks rather than 5-9 chunks.

Multi-Store Model of Memory

• The Multi-Store Model (MSM) illustrates how memory is stored, transferred, retrieved, and forgotten.
• Three stores exist: sensory register, short-term memory, and long-term memory.
• The sensory register has a sub-store for each of the 5 senses, like the echoic store for auditory information.
• Sensory register has a huge capacity with a duration of less than half a second.
• Information only transfers from the sensory register to STM if attention is paid.
• STM is acoustically encoded, has a capacity of 7+/- 2 items, and lasts 18-30 seconds.
• Maintenance rehearsal keeps information in STM; prolonged rehearsal moves it to LTM. Lack of rehearsal causes forgetting.
• LTM is semantically encoded, has unlimited capacity, and can last over 46 years.
• Retrieval transfers information back to STM so it can be recalled.
• Different types of LTM (procedural, semantic, episodic) are not represented in the MSM.
• MSM suggests the amount of maintenance rehearsal is key, while Craik and Watkins (1973) suggest that elaborative rehearsal is more important for transfer to LTM.
• MSM highlights qualitative differences between STM and LTM such as duration and encoding.
• The MSM incorrectly depicts STM as a single store.
• Shallice and Warrington's amnesiac patient KF had poor auditory STM recall but good visual recall, suggesting multiple types of STM.

Types of Long-Term Memory

• Long-term memory has 3 types: episodic, semantic, and procedural.
• Episodic memory includes personal events and details like when, where, and who was involved.
• Semantic memory encompasses knowledge of the world, including understanding words and concepts.
• Procedural memories involve learned skills such as swimming.
• Episodic and semantic memories require conscious recall, whereas procedural memories are unconsciously recalled.
• Petersen et al showed semantic memories were recalled from the left prefrontal cortex, and episodic memories from the right prefrontal cortex.
• Understanding different types of LTM has practical applications.
• Belleville et al note that mild cognitive impairments often affect episodic memories, suggesting targeted treatments can be developed through understanding the different types.
• Cohen and Squire distinguish between declarative (conscious recall) and non-declarative memories.
• Tulving's depiction of LTM may not be entirely accurate, due to alternative categorizations.
• Cases such as HM and Clive Wearing demonstrate that one type of LTM can be impaired while others remain unaffected.

The Working Memory Model

• Working Memory Model (WMM) states that STM is composed of the central executive, phonological loop, visuo-spatial sketchpad, and episodic buffer.
• Central executive allocates tasks to slave systems, it has limited processing capacity.
• Phonological loop processes auditory information and uses the articulatory process (inner voice) and phonological store (inner ear) for maintenance rehearsal.
• Visuo-spatial sketchpad (VSS) processes visual and spatial information; separated into the inner scribe and visual cache. The capacity of the VSS is around 4-5 chunks (Baddeley).
• Episodic buffer integrates data from other stores and links STM to LTM.
• Central executive hasn't been precisely defined making its accuracy questionable.
• Shallice and Warrington's study of KF shows the possibility of separate components for processing auditory and visual stimuli .
• Dual-task performance studies show decreased effectiveness when a visual and verbal task are performed simultaneously.
• Neuroscanning evidence by Braver et al points to a positive correlation between increased cognitive load/task difficulty and prefrontal cortex activation.

Explanations of Forgetting: Interference

• Interference is when one memory blocks the recall of another, causing forgetting or distorted perceptions.
• Interference can be retroactive (new blocks old) or proactive (old blocks new).
• McGeoch and McDonald's 1931 study had participants recall lists of words. Those recalling synonyms had lower recall compared to the control group, exemplifying retroactive interference.
• Forgetting increases when memories/materials are similar.
• Interference studies may have low mundane realism due to artificial stimuli.
• Demonstrating interference in lab experiments increases the validity of the theory through standardization and controlled conditions.
• Baddeley and Hitch found rugby players' recall of last game was related to number of games played instead of time, exemplifying retroactive interference.
• Interference studies may lack generalizability due to short time frames between learning and recall, which lack mundane realism.

Explanations of Forgetting: Retrieval Failure

• Retrieval failure arises when the cues present during encoding aren't present during recall, following Tulving's encoding specificity principle (ESP).
• Forgetting can be context-dependent or state-dependent.
• Godden and Baddeley's 1975 study showed divers recalled better in matching underwater/on land conditions, showing context-dependent forgetting.
• Carter and Cassaday's 1998 study altered internal cues with anti-histamines, finding better recall in matching conditions, demonstrating state-dependent forgetting.
• Retrieval failure might be a main reason behind forgetting from LTM, with experimental design increases validity.
• Retrieval failure studies may lack ecological validity because it is difficult to find context effects of real-life that are distinct.
• Godden and Baddeley's repeated study used recognition rather than recall: finding that recognition accuracy in both matched and non-matched conditions had no notable difference.
• Encoding specificity principle suffers from possible cyclical reasoning, with differences between cues possibly causing retrieval failure.

Factors Affecting the Accuracy of Eyewitness Testimony: Misleading Information

• Eyewitness testimony can be reduced through misleading (incorrect) information in the form of leading questions and post-event discussions.
• Loftus and Palmer (1974) showed participants crash films and got speed estimates through questions with critical verb manipulations. It was those exposed to smashed who gave a speed estimate that was 8.7mph greater than those who'd heard 'contacted'.
• Leading questions can exhibit response bias or change the eyewitness' memory of the crime, such as report of broken glass (substitution explanation).
• Post-event discussions between co-witnesses can be influenced by media and expectations.
• Gabbert et al (2003) found 71% inaccuracy rate of information gained through discussions from crime scene between paired viewers (0% control rate with solo viewers).
• Post-event discussions exemplify 'memory conformity', with the urge to believe that the other person is right.
• Young targets can be affected by one age bias that influences EWT.
• Demand characteristics may reduce the reliability of the findings, participants want be as helpful and attentive as possible.
• Tasks or artificial stimuli from research does not expose participants to the anxiety of crime.

Factors Affecting the Accuracy of Eyewitness Testimony: Anxiety

• Anxiety is a physiological response to external pressures. It can have a positive or negative effect on EWT.
• Johnson and Scott (1976) demonstrated the negative effect of anxiety with less recall rates in the high-anxiety condition with bloody paper-knife with use of lower 16% results.
• Studies support the idea that heightened anxiety drives focus for high attention.
• Tunnel theory of memory includes the weapon focus effect, with focus on a high anxiety source.
• Yuill and Cutshall (1986) eyewitnesses in real lives had an 11% higher accuracy recall in the high anxiety state after a shooting.
• Yerkes-Dodson Law includes an inverted-U relationship between arousal and increasing performance.
• Weapon focus effect may instead test for surprise rather than anxiety.
• Unusualness, such as a raw chicken in a hairstyling salon, explains the idea of weapon focus.
• Ethical issues are a cause for concern alongside the right to be protected from psychological harm.
• Real-life study outcomes lead to biasing effects of extraneous variables that have not been controlled.

Improving the Accuracy of Eyewitness Testimony: Cognitive Interviews

• The cognitive interview is for questioning eyewitnesses in order to increase their recall rates.
• Tell them to report everything.
• Remind them to reinstate the context.
• Have them change perspectives.
• Reverse the order of events.
• The enhanced cognitive interview focuses on social dynamics between eyewitness and interviewer (Fisher et al 1987).
• Cognitive interviews may have little practical value as it is requiring expert training.
• The CI can increase or decrease recall by a higher percentage and accuracy than eyewitness testimonies (Kohnken et al 1999).
• The entire Cl need not be used for the best recall of memory (Milne and Bull 2002).