Memory Systems and Processes: Study Notes for Psychology Students

Memory Systems

Introduction to Memory

Memory is the process by which information is encoded, stored, and retrieved. It allows organisms to retain information from past experiences to guide future behavior and cognition.

• Encoding: Transforming sensory input into a form that can be stored.

• Storage: Maintaining encoded information over time.

• Retrieval: Accessing stored information when needed.

Atkinson-Shiffrin Model (1968)

This influential model describes memory as consisting of three distinct systems:

• Sensory Memory: Large capacity, very brief duration (300–500 ms).

• Short-Term Memory (STM): Limited capacity (7±2 items), short duration (15–30 seconds).

• Long-Term Memory (LTM): Essentially unlimited capacity and duration.

Example: Remembering a phone number long enough to dial it uses STM; remembering your childhood address uses LTM.

Sensory Memory

• Iconic Memory: Visual sensory memory.

• Echoic Memory: Auditory sensory memory.

• Whole vs. Partial Report (Sperling, 1960): Demonstrated that more information is available in sensory memory than can be reported.

Short-Term Memory (STM)

• Capacity: 7±2 items (Miller's Law); can be increased by chunking (grouping items into meaningful units).

• Example: Remembering 4167362100 as 416-736-2100 (chunking into area code, prefix, and line number).

• Duration: About 15–30 seconds without rehearsal (Brown-Peterson task).

• Rehearsal: Maintains information in STM.

STM Capacity and Expertise

• Expertise (e.g., chess masters) can improve STM for domain-specific information but not for random arrangements.

• Lumosity controversy: Claims about brain training improving STM are debated.

Memory Decay and Retention

• Memory Decay: Information is lost over time if not rehearsed.

• Spacing Effect: Spaced practice leads to better long-term retention than massed practice.

• Ebbinghaus Forgetting Curve: Shows rapid initial forgetting, which slows over time.

Baddeley & Hitch Working Memory Model (1974, 2000)

• Central Executive: Directs attention and coordinates subsystems.

• Phonological Loop: Stores and rehearses verbal information.

• Visuospatial Sketchpad: Maintains visual and spatial information.

• Episodic Buffer: Integrates information across domains and links to LTM.

Long-Term Memory (LTM)

• Implicit (Nondeclarative) Memory: Unconscious memory, including procedural skills and conditioning.

• Explicit (Declarative) Memory: Conscious recall of facts (semantic) and events (episodic).

Implicit Memory	Explicit Memory
Procedural (skills, habits)	Semantic (facts)
Priming	Episodic (events)
Classical/Operant Conditioning
Non-associative (habituation, sensitization)

Implicit Memory

• Associative: Classical and operant conditioning.

• Non-associative: Habituation and sensitization.

• Priming: Change in response to a stimulus due to prior exposure.

• Procedural: Skills and habits (e.g., riding a bike).

Episodic and Semantic Memory

• Episodic: Memory for personal events, including mental time travel.

• Semantic: Memory for facts and general knowledge.

• Neural Basis: Medial temporal lobes (especially hippocampus) and cerebral cortex are critical for explicit memory.

• Long-Term Potentiation (LTP): "Neurons that fire together, wire together" (Hebb's Law).

Amnesia

Types of Amnesia

• Anterograde Amnesia: Inability to form new long-term memories.

• Retrograde Amnesia: Inability to recall past long-term memories.

• Often results from damage to the medial temporal lobes (e.g., hippocampus).

Example: Patient H.M. (Scoville & Milner, 1957) had bilateral removal of the hippocampus, resulting in severe anterograde amnesia but preserved working memory and old long-term memories.

Encoding & Retrieval

Serial Position Effect

• Primacy Effect: Better recall for items at the beginning of a list (due to LTM encoding).

• Recency Effect: Better recall for items at the end of a list (due to STM).

• Maintenance Rehearsal: Simple repetition to keep information in STM.

Levels of Processing (Craik & Tulving, 1975)

• Elaborative Rehearsal: Attaching meaning to information enhances memory.

• The deeper the processing (e.g., semantic analysis), the better the memory performance.

• Example: Remembering words by their meaning rather than their appearance or sound.

Context-Dependent Memory

• Encoding Specificity Principle: Memory is best when retrieval conditions match encoding conditions.

• State-Dependent Memory: Recall is better when physiological states match.

• Mood-Dependent Memory: Recall is better when moods match.

• Context-Reinstatement: Environmental context at encoding and retrieval affects memory (Godden & Baddeley, 1975).

Experimental Evidence

• Studies show that imagining the original learning context or matching test and study environments can improve recall.

• Self-relevance effect: Information related to oneself is remembered better.

Statistical Significance in Memory Research

• p-value: Probability that observed results occurred by chance. A value greater than 0.05 typically means results are not statistically significant.

References

• Atkinson, R. C., & Shiffrin, R. M. (1968). Human memory: A proposed system and its control processes.

• Craik, F. I. M., & Tulving, E. (1975). Depth of processing and the retention of words in episodic memory.

• Baddeley, A. D., & Hitch, G. (1974). Working memory.

• Godden, D. R., & Baddeley, A. D. (1975). Context-dependent memory in two natural environments.

• Scoville, W. B., & Milner, B. (1957). Loss of recent memory after bilateral hippocampal lesions.

• Sperling, G. (1960). The information available in brief visual presentations.