Memory simplified

Multistore Model of Memory

Atkinson and Shiffrin (1968)

• A theoretical cognitive model explaining how the memory system processes information.

• Three memory stores: sensory register, short-term memory (STM), and long-term memory (LTM).

Sensory Register

• Function: Receives raw sense impressions.

• Attention: Passes information to STM.

• Coding: Modality-specific (related to senses).

• Capacity: Very large, holding all sense impressions in each moment.

• Duration: Very short, approximately 250 milliseconds, but varies per sense.

Short-Term Memory (STM)

• Function: Receives information from the sensory register via attention or from LTM via retrieval.

• Maintenance: Keeps information active through maintenance rehearsal (repetition) or transfers it to LTM by linking it to existing LTM content.

• Rehearsal Types: Elaborative rehearsal (linking to LTM) and maintenance rehearsal (repetition).

• Coding: Acoustic.

• Duration: Approximately 18 seconds.

• Capacity: 7 ± 2 items (Miller's Magic Number).

• Loss of Information: Displacement (new information replaces old) or decay (loss over time).

Long-Term Memory (LTM)

• Function: Long-term storage of information.

• Duration: Very long, potentially permanent.

• Capacity: Theoretically unlimited.

• Retrieval: Information must be passed back to STM to be used.

• Coding: Semantically (in terms of meaning).

• Forgetting: Information appears inaccessible rather than lost.

Evaluations of the Multistore Model (MSM)

Strengths

• Serial Position Effect: Glanzer and Kunitz found that words at the beginning (primacy effect - LTM) and end (recency effect - STM) of word lists are more easily recalled. Middle words are displaced.

• Sensory Register Capacity & Duration: Sperling's experiment showed that briefly flashed grids had high recall (75% for a random row), suggesting large capacity and short duration.

Weaknesses and Criticisms

• Coding in STM and LTM: Baddeley found that immediate recall is worse for acoustically similar words, and recall after 20 minutes is worse for semantically similar words. This supports acoustic coding in STM and semantic coding in LTM.

• STM Capacity: Jacobs found recall for lists of letters averaged 7 items, and 9 for numbers. This suggests a limited capacity of 7 ± 2 items, but chunking can improve it.

• STM Duration: Peterson and Peterson found that recall of trigrams (e.g., HFR) was less than 10% after 18 seconds with an interference task, indicating a short duration.

• LTM Capacity: Wagner's diary study (240 events over 6 years) showed 75% recall after 1 year and 45% after 5 years, suggesting a large capacity.

• LTM Duration: Bahrick found 90% recall of school friends' names from photos after 15 years and 80% after 48 years, suggesting a long duration.

• Artificiality: Cognitive tests are often artificial (low mundane realism) and conducted in lab environments (low ecological validity).

• Simplistic View of LTM: The MSM does not account for different types of LTM.

• STM as Passive: The MSM portrays STM as a passive store, while the working memory model explains STM as an active system.

• Fixed Capacity: Capacity can be altered by age and practice, challenging the view of a fixed STM capacity.

Types of Long-Term Memory

Long-term memory is the storage of memories over a long time.

Declarative (Explicit) vs. Non-Declarative (Implicit)

• Declarative (Explicit): Memories that can be consciously accessed and expressed in words.

• Non-Declarative (Implicit): Memories not consciously recalled, difficult to explain in words.

Episodic Memory

• Definition: Experiences and events that are timestamped with a reference to time and place.

• Nature: Autobiographical.

• Recall: Consciously recalled (declarative).

• Influenced By: Emotion.

• Brain Areas: Hippocampus and prefrontal cortex.

Semantic Memory

• Definition: Facts, meanings, and knowledge.

• Recall: Consciously recalled (declarative).

• Strength: Comes from processing depth; lasts longer than episodic.

• Timestamping: Not timestamped.

• Relationship to Episodic: Episodic memories can become semantic over time.

• Brain Areas: Frontal cortex.

Procedural Memory

• Definition: Unconscious memories of skills (e.g., riding a bike).

• Recall: Not consciously recalled (non-declarative).

• Resistance to Forgetting: More resistant to forgetting than episodic or semantic memories.

• Acquisition: Often learned in childhood.

• Brain Areas: Motor cortex and cerebellum.

Evaluations of Types of LTM

Evidence for Distinct Systems

• Vargha-Khadem et al.: Children with hippocampus damage had episodic amnesia but could still learn semantic information, suggesting different brain regions for each type of memory.

• Clive Wearing: Retrograde amnesia affected his episodic memory (couldn't remember his musical education or wedding) but preserved semantic (knew he was a musician and married) and procedural memory (could play the piano)

  • Anterior grade amnesia prevented new episodic or semantic memory encoding, but he could gain new procedural memories through repetition.

Criticisms

• Generalizing Idiographic Studies: Problematic to generalize from clinical case studies to the wider population. Unknown issues could be unique to the individual.

• Neuroimaging Support: Tulving's neuroimaging studies have identified brain areas associated with each type of LTM in healthy brains, supporting the case study findings.

• Overlap Between Types: Episodic and semantic memories are both declarative; episodic memories can become semantic over time.

• Automatic Language: We can produce automatic language, which combines semantic and procedural memory.

Working Memory Model

Baddeley and Hitch (1974)

• A theoretical cognitive model of information processing designed to replace the STM store in the MSM.

• Description: An active processor made of multiple stores, unlike the MSM's passive and unitary STM.

Components

1. Central Executive (CE)

   • Function: Head of the model; receives sense information, controls attention, and filters information.

   • Capacity: Limited to about four items.

   • Processing: Can only deal with one strand of information at a time.

2. Phonological Loop (PL)

   • Function: Processes sound information; acoustic coding.

   • Components:

     • Primary Acoustic Store (inner ear): Stores words recently heard.

     • Articulatory Process (inner voice): Stores information via subvocal repetition.

   • Capacity: 2 seconds.

3. Visuo-Spatial Sketchpad (VSSP)

   • Function: Processes visual and spatial information.

   • Components:

     • Visual Cache: Passive store of form and color.

     • Inner Scribe: Active store of relationships in 3D space.

4. Episodic Buffer

   • Addition: Added in 2000.

   • Function: General store to hold and combine information from the VSSP, PL, CE, and LTM.

Evaluations of the Working Memory Model

Strengths

• Dual-Task Performance: Baddeley found that performing two visual tasks or a visual and verbal task showed better performance when the tasks didn't use the same processing systems.

• Case Study KF: KF had selective impairment to verbal STM after brain injury but intact visual functioning, supporting separate PL and VSSP subsystems.

• Neuroimaging Evidence: Parakrama et al. found more prefrontal cortex activation when integrating spatial and verbal information and more posterior brain region activation when not integrated, supporting the episodic buffer.

• Word Length Effect: Baddeley found that participants recalled more monosyllabic words than polysyllabic words, supporting the idea that the phonological loop's capacity is about 2 seconds (word length effect).

• Active Processing: The working memory model seems more accurate than the MSM's STM component in describing how memory is used as an active processor.

Weaknesses

• External Validity: Memory tasks lack mundane realism and are artificial, so findings may not generalize to real-life memory use.

• Central Executive Criticisms: The central executive is a poorly defined concept, and Baddeley admits it needs further development.

• Indirect Observation: The processes of memory are not directly observable; inferences are assumptions about cognitive processes that could be incorrect.

Explanations for Forgetting

Interference Theory

• Definition: Forgetting occurs because long-term memories become confused or disrupted by other information during coding.

Types of Interference

1. Proactive Interference

   • Direction: Old information disrupts new information (works forward in time).

   • Mechanism: Old information already stored interferes with recalling something new.

2. Retroactive Interference

   • Direction: New information disrupts old information (works backward in time).

   • Mechanism: New information being stored interferes with the recall of old information.

Factors Influencing Interference

• Similarity: Interference is more likely when the two pieces of information are similar due to response competition.

• Time Sensitivity: Interference is less likely when there is a large gap between learning and retrieval.

Retrieval Failure

• Definition: Forgetting happens due to the absence of appropriate cues (cue-dependent forgetting).

Cues

• Description: Prompts encoded at the same time as the information.

• Encoding Specificity Principle: States that cues must be present at encoding and retrieval to aid memory.

Types of Cues

1. Context-Dependent Cues

   • Description: Aspects of our external environment (sight, sound, smells).

   • Effect: Being in a different place inhibits memory because of a lack of environmental cues.

2. State-Dependent Cues

   • Description: Aspects of our internal environment (emotions, drug states, states of arousal).

   • Effect: Being in a different emotional state inhibits memory because of a lack of state-dependent cues.

3. Category/Organizational Cues

   • Description: Cues that relate to the organization or category of memories.

   • Effect: The lack of organization cues inhibits memory.

Evaluations of Explanations for Forgetting

Strengths

• Retroactive Interference: Smith sent questionnaires to people of various ages and included a map of their school area without street names. Those who moved home more often recalled fewer street names.

• Proactive Interference: Greenberg and Underwood found that the more word pairs participants learned, the fewer word pairs they correctly recalled.

• Context-Dependent Cues: Godden and Baddeley found that recall was best when divers learned and were tested in the same environment (underwater or on land).

• State-Dependent Cues: Overton found that recall was best when participants were in the same internal state (drunk or sober) during learning and recall.

• Category-Dependent Cues: Tulving and Pearlstone found that participants recalled significantly more words when provided with category cues.

• Practical Applications: Students can develop effective revision strategies, and context cues have been used in developing the cognitive interview.

Weaknesses

• Limited Scope of Interference: Interference only explains forgetting when two sets of information are similar and learned close together in time.

• Temporary Loss: Interference and cue failure may only explain temporary losses, not permanent ones.

• Ecological Validity: Some research lacks ecological validity.

Factors Affecting the Accuracy of Eyewitness Testimony (EWT)

Reconstructive Memory

• Bartlett argued that memory is not an accurate recording of events but is reconstructed during recall, potentially leading to errors and confabulations. Schemas influence this reconstruction.

Misleading Information

1. Leading Questions

   • Definition: Questions that imply a particular answer.

   • Effects: Can influence how memory is recalled due to:

     • Substitution Bias: An actual change to the memory.

     • Response Bias: Emotional pressure to give a particular response.

2. Post-Event Discussion (Contamination)

   • Definition: Recall of events by one witness alters the accuracy of another witness's recollection.

   • Memory Conformity: Witnesses go along with others' accounts for social approval.

Anxiety

• Definition: A mental state of arousal with feelings of extreme concern, tension, and physiological changes.

• Negative Effects: High anxiety levels may decrease recall due to the weapons effect (witnesses focus on the weapon rather than the criminal's face).

• Positive Effects: High anxiety levels may increase recall by improving alertness and awareness.

• Yerkes-Dodson Law: EWT accuracy increases as anxiety rises, but at a certain point, anxiety becomes too high, leading to stress and distraction, which lowers accuracy.

Evaluations of Factors Affecting EWT

Strengths

• Misleading Information - Leading Questions: Loftus and Palmer's car crash experiment showed that the verb used (smashed, collided, bumped, hit, contacted) influenced the speed estimation.

• Misleading Information - Post-Event Discussion: Gabbert et al. found that when participants discussed the videos they had seen, 71% included information not in their video in their EWT.

• Anxiety: Johnson and Scott found that participants were less accurate in identifying a man holding a bloody knife (high anxiety) compared to a man holding a pen (low anxiety).

• Real-life Application: Research on the limitations of EWT has led to the development of the cognitive interview.

Weaknesses

• Misleading Information - Post-Event Discussion: Bodner found that warning participants about the dangers of post-event discussion reduced the effect of this.

• Lab-Based Research: Lab-based research has low validity when applied to real eyewitness testimony because it lacks emotional impact.

• Anxiety: Yuille and Cutshall found that in a real-life shooting, witnesses resisted misleading information, and those closest to the shooter (most stressed) had the most accurate EWT.

• Demand Characteristics: Participants may pick up on the language used and feel pressure to give an answer they think will help the researcher.

• Ethical Issues: Research that deceives participants and causes anxiety breaks ethical guidelines (protection from harm, informed consent).

Improving the Accuracy of Eyewitness Testimony

Limitations of Standard Interview

• Fisher et al. observed that police ask quick, direct, and closed questions, interrupt witnesses, and don't allow them to talk freely.

The Cognitive Interview (CI)

• Fisher and Geiselman suggested the cognitive interview as an improvement.

Elements of the Cognitive Interview

1. Context Reinstatement: Mentally returning to the crime scene to trigger environmental, emotional, and contextual cues.

2. Report Everything: Mentioning all details, even if they seem irrelevant.

3. Recall from a Changed Perspective: Considering the perspective of other witnesses or the perpetrators to disrupt schema.

4. Recall in Reverse Order: Switching to different chronology timelines to check accuracy and challenge expectations.

Evaluations of the Cognitive Interview

Strengths

• Real-World Effectiveness: Geiselman et al. found that detectives trained in the cognitive interview produced 47% more information in real interviews after their training.

• Meta-Analysis Support: Kohnken et al.'s meta-analysis of 42 CI studies found a significant increase in the amount of correct information recalled.

Weaknesses

• Increased Errors: Kohnken et al. also found a significant increase in incorrect information recalled, resulting in a similar accuracy rate for CI and standard interviews.

• Component Effectiveness: Mine and Hibs found each aspect of the CI produces similar levels of recall, with context reinstatement and reporting everything producing more correct recall.

• Time and Resource Intensive: The CI is time-consuming, requires significant training and investment, and diverts officers from their normal work.

• Limited Usefulness: The CI is not effective in improving the recognition of suspects in identity parades and from photographs.

• Child Applicability: The CI is not effective with very young children due to egocentrism. Holliday created a modified CI for children.