Memory Models and Processes: Atkinson–Shiffrin, Working Memory, and Semantic Networks

Atkinson-Shiffrin Model

A foundational model of memory proposing three stages: sensory memory (brief sensory storage), short-term memory (active manipulation of information), and long-term memory (permanent storage). Information flows sequentially through these stages via encoding, storage, and retrieval.

Encoding

The process of translating external information into an internal mental representation for storage.

Storage

The maintenance of a memory representation over time, preserving encoded information within the mind.

Retrieval

The process of accessing stored memory representations for use in thought, reasoning, or action.

Sensory Memory

The first stage of memory—briefly holds sensory information (e.g., visual or auditory) for 200-500 ms. It has virtually limitless capacity but extremely short duration.

Short-Term Memory (STM)

A temporary storage system with limited capacity (about 7±2 items) and a duration of 2-5 seconds. Information can decay unless actively rehearsed.

Long-Term Memory (LTM)

A memory system with virtually unlimited capacity and long duration, capable of storing information for years or a lifetime.

Short-Term vs. Long-Term Memory

STM and LTM are qualitatively different: STM is fragile, transient, and capacity-limited ("like wet sand"), while LTM is durable and structured ("a hall of prophecies").

Subdivisions of Long-Term Memory

Includes implicit (unconscious) and explicit (conscious) systems—implicit covers skills and conditioned responses; explicit covers semantic (facts) and episodic (events) memory.

Implicit Memory

Memory expressed through behavior without conscious awareness (e.g., procedural skills, conditioned responses).

Explicit Memory

Conscious recollection of facts or events, subdivided into semantic (knowledge) and episodic (personal experience) components.

Semantic Memory

Memory for facts, meanings, and general knowledge, not tied to specific experiences (e.g., knowing the capital of France).

Episodic Memory

Memory for personal experiences and events, organized temporally and tied to one's self and perception (e.g., remembering your first date).

Visuospatial Memory

The ability to create and manipulate mental images ("mind's eye"), representing spatial and visual information in analog format.

Rehearsal

Repetition of items to maintain them in short-term memory and transfer to long-term memory.

Chunking

Combining separate pieces of information into meaningful units (e.g., "F B I V I P G N P C B S" → "FBI VIP GNP CBS") to increase STM capacity.

Peterson & Peterson (1959)

Demonstrated that STM decays rapidly without rehearsal—participants asked to count backward by threes during retention showed steep forgetting over seconds.

Wickens (1972)

Showed release from proactive interference—recall improved when semantic category of items changed, proving that interference in STM is meaning-based.

Proactive Interference

When older information interferes with learning or recalling new information.

Release from Proactive Interference

Improved recall when new information differs semantically from previously learned material.

Serial Position Effect

Tendency to recall first (primacy) and last (recency) items in a list better than those in the middle.

Primacy Effect

Enhanced recall for items at the beginning of a list, attributed to rehearsal transferring them to long-term memory.

Recency Effect

Enhanced recall for items at the end of a list, attributed to their presence in short-term memory at retrieval.

Poltrock & MacLeod (1977)

Showed that recency effects disappear when recall is delayed, confirming that recency depends on STM while primacy depends on rehearsal and LTM.

Working Memory

A dynamic, multi-component system for temporary storage and manipulation of information, consisting of the central executive, phonological loop, and visuospatial sketchpad.

Central Executive

The supervisory system in working memory that allocates attention and coordinates information from subsidiary systems.

Phonological Loop

The verbal component of working memory that holds and rehearses speech-based information ("inner voice").

Visuospatial Sketchpad

The visual and spatial component of working memory that manipulates imagery ("mind's eye").

Phonological Similarity Effect

Immediate recall is worse for items that sound alike (e.g., "dog," "bog"), showing phonological coding in STM.

Word Length Effect

Recall decreases as the spoken length of words increases, since longer words take more time to rehearse.

Articulatory Suppression

Saying irrelevant speech while studying disrupts phonological rehearsal and impairs recall.

Irrelevant Speech Effect

Hearing irrelevant spoken words during encoding disrupts immediate recall even if the words are to be ignored.

Logie et al. (1990)

Demonstrated selective interference: performance worsens when two tasks use the same subsystem (e.g., verbal + verbal or visual + visual), supporting distinct WM components.

Semantic Memory Organization

Organized by association (concepts linked semantically) and typicality (more prototypical examples accessed faster).

Lexical Priming

Faster recognition for semantically related words (e.g., "nurse-doctor") than unrelated ones, showing associative network structure.

Meyer & Schvaneveldt (1971)

Used lexical decision tasks to show that semantically related word pairs are recognized faster, providing evidence for semantic network links.

Spreading Activation

The process by which activation of one concept node spreads to related concepts, increasing their accessibility.

Hierarchical Models of Semantic Memory

Represent semantic knowledge as levels of nodes and links (superordinate → subordinate). Predict that verification time increases with distance in hierarchy.

Problems with Hierarchical Models

Typicality effects violate strict hierarchies—people verify "a robin is a bird" faster than "a chicken is a bird," and superordinate properties don't always apply (e.g., "penguins fly").

Adaptive Control of Thought (ACT) Model

A propositional model where nodes represent types/tokens and links have variable strength. Explains spreading activation and type-token distinctions.

Strengths of ACT Model

Accounts for spreading activation and predicts new effects (e.g., fan effect), integrating symbolic and propositional representations.

Weaknesses of ACT Model

Symbolic structure is psychologically plausible but biologically implausible—unclear how such architecture maps to neural networks.

Parallel Distributed Processing (PDP) Model

Represents knowledge as patterns of activation across interconnected units. Nodes act like neurons; learning occurs by adjusting connection weights.

Strengths of PDP Models

Neurologically plausible, adaptive (they can learn), and capable of representing graded, dynamic knowledge structures.

Weakness of PDP Models

Subject to catastrophic interference—new learning can overwrite old information ("penguins can swim" → "canaries can swim").

Purpose of Modeling Cognitive Systems

Models make assumptions explicit, generate predictions, and provide tools for analyzing cognition quantitatively.

Episodic Memory

Memory for personally experienced events, organized in time and usually containing perceptual and contextual details.

Childhood Amnesia

Inability to recall autobiographical events from before ages 3-4, due to immature hippocampus/prefrontal cortex and underdeveloped rehearsal/metamemory.

Carver & Bauer (2001)

Taught 10-month-olds novel actions; 3 months later they still imitated them, showing early memory formation but rapid forgetting.

Bruce et al. (2000)

Found that genuine autobiographical recall may not occur until age 5-6, implying earlier "memories" are reconstructions, not true episodic recollections.

End of Childhood Amnesia

Estimated between ages 2-2.5 when queried about sibling birth, but reliability and accuracy remain debated.

Wang (2008)

Tested bicultural Asian American students primed with American vs. Asian identity. "American" primes led to more autonomous memories, "Asian" primes to more social ones—showing cultural priming shapes autobiographical recall.

Cultural Priming and Self-Concept

Self and memory are reciprocal—cultural context cues schema-consistent memories, shaping the self that is recalled.

mplicit Memory

Memory that influences behavior without conscious awareness or intent, evidenced through performance changes rather than recall.

Explicit Memory

Conscious, intentional recollection of information (facts, events, or experiences).

Implicit Memory in Amnesiacs

Demonstrates learning without awareness—patients show skill improvement (e.g., mirror tracing) despite no recollection of practice.

Claparède (1911)

Pricked an amnesiac patient's hand during greeting; next day she refused to shake his hand though she couldn't recall why—showing implicit memory for threat despite explicit amnesia.

Patient H.M. (Henry Molaison)

Had hippocampus removed, resulting in severe anterograde amnesia. Could not form new declarative memories but learned mirror-tracing tasks, showing preserved procedural memory.

Cohen & Squire (1980)

Showed amnesiacs could improve mirror reading speed at the same rate as controls but failed to recognize the words—revealing dissociation between procedural and declarative memory.

Graf, Squire, & Mandler (1984)

Found amnesiacs performed normally on word stem completion (implicit) despite poor recognition (explicit), showing that implicit memory operates without awareness.

Implicit Memory in Non-Amnesiacs

Demonstrated through priming—people show faster responses to repeated or related stimuli even without conscious recollection.

Subliminal Priming

Exposure to stimuli below conscious threshold affects later perception or behavior (e.g., "table" primes "chair").

Jacoby et al. (1989)

Participants judged previously seen names as more "famous," mistaking familiarity for fame—evidence of implicit memory influencing conscious judgment.

Finn et al. (2016)

Found children display adult-like procedural memory (implicit) before fully developed declarative memory (explicit), showing developmental dissociation between systems.

Implicit vs. False Memory

Implicit = unintentional retention of experienced stimuli; False = confident recollection of non-experienced stimuli.

False Memory

Remembering something that never occurred, often due to associative activation or misleading information.

Deese-Roediger-McDermott (DRM) Paradigm

Presenting related word lists (e.g., "needle," "thread," "pin") leads participants to falsely recall non-presented but related "lure" words (e.g., "sewing"), due to semantic activation.

Explaining False Memory

Semantic activation spreads to related nodes, making them feel familiar enough to be misattributed to experience.

Forgetting Curve

Discovered by Ebbinghaus (1885) — forgetting is rapid initially then levels off; relearning is faster than original learning, and spacing increases retention.

Depth of Processing

Craik & Tulving (1975) found that semantic (deep) processing produces better recall than shallow (structural or phonemic) processing.

Otten & Rugg (2001)

Used fMRI to show deep (semantic) processing activates distinct brain areas compared to shallow processing—qualitatively different, not just more intense.

Organization and Memory

Structured information is recalled better; organization provides retrieval cues and enhances encoding efficiency.

Bower et al. (1969)

Showed that hierarchically organized material was recalled almost twice as well as random lists, illustrating benefits of semantic structure.

Elaboration

Adding meaningful connections or imagery improves memory, especially if elaboration is relevant to the material.

Stein et al. (1978)

Found sentences with relevant elaboration ("...by the short man who looked the child in the eye") had higher recall (69%) than irrelevant elaboration (33%).

Serial Reproduction

Method by Bartlett (1932) showing that recall of unfamiliar stories becomes distorted toward cultural expectations—basis of schema theory.

Schema Theory

Suggests memory is reconstructive—people fill in missing details with schema-consistent information and omit inconsistent details.

Encoding-Retrieval Interaction

Memory performance depends on context match between learning and recall environments.

Godden & Baddeley (1975)

Scuba divers recalled more words when learning and test environments matched (land-land or underwater-underwater), demonstrating context-dependent memory.

Expertise and Memory

Experts show selective recall for relevant or abnormal patterns, driven by schemas and chunking strategies.

Myles-Worsley et al. (1988)

Radiologists remembered abnormal X-rays better than normal ones—expertise enhances schema-based attention but filters out uninformative stimuli.

Gender and Memory

Canli et al. (2002) found women show same-hemisphere amygdala activation for emotional encoding and retrieval, men show cross-hemispheric—explaining stronger emotional memory in women.

Synesthesia

A condition where stimulation of one sense involuntarily triggers another (e.g., seeing colors when hearing sounds). Enhances memory via multimodal encoding.

Luria (1968)

Documented "S.", a man with synesthesia and near-perfect recall, who used imagery and the method of loci to store vast information.

Yarrow & Ward (2007)

Found synesthetes outperform controls on memory tasks—multisensory integration enhances encoding and retrieval.

Spacing Effect

Distributed practice yields better long-term retention than massed practice, even over years.

Bahrick et al. (1993)

Family study showing spaced foreign-word practice produced superior retention after up to 5 years—spacing benefits endure across long intervals.

Schemas

Organized frameworks of knowledge that shape interpretation and memory. They fill in gaps and guide comprehension.

Bransford & Johnson (1972)

Gave participants a vague passage; those told the topic beforehand (e.g., "Flying a kite") recalled more—schemas improve encoding when activated before learning.

Schema-Driven False Memory

Brewer & Treyens (1981) found students falsely recalled seeing "books" in a professor's office that had none—schemas bias memory toward expected items.

Lampinen et al. (2001)

Showed high confidence in false schema-based memories—people report "specific recollections" for nonexistent details.

Story Schemas

Typical story structures (beginning, goal, attempt, outcome, ending) facilitate comprehension and recall.

Mandler & Goodman (1982)

Found that reordering story events slowed reading, showing readers expect schema-consistent narrative order.

Schema Inconsistency

When information violates expectations, people distort it to fit known schemas.

Barrett & Keil (1996)

Participants retelling stories about God added human limitations ("God couldn't hear the birds"), showing assimilation to human schemas.

Scripts

Event-based schemas representing routine sequences (e.g., dining, boarding a plane).

Bower et al. (1979)

Showed participants recalled omitted actions consistent with event scripts (e.g., "seeing a doctor") even if not presented.

Development of Maintenance Rehearsal

Flavell et al. (1966) found that rehearsal frequency increases with age—young children don't use inner speech effectively, limiting memory span.

Source Monitoring

Ability to identify the origin of one's memories (perceived, told, inferred).

Gopnik & Graf (1988)

Found young children confused "told" vs. "inferred" information, showing poor source tracking.