Jill Price has highly superior autobiographical memory.
She can remember every day of her life since February 5th, 1980.
When tested with random dates, she can recall exact details (Parker et al., 2006).
Jill has hyperthymesia, a rare syndrome where people can recall vast amounts of episodic memory in vivid detail.
There are about 60-80 documented cases worldwide.
For some, hyperthymesia can be a curse, making it difficult to forget negative past experiences.
Some individuals with hyperthymesia use calendars to determine the current day.
Jill's experiences highlight the extraordinary nature of memory and the importance of forgetting as a normal function.
Overview of This Week's Videos
Part 1: Ways of thinking about memory
Part 2: Sensory memory and short-term memory
Part 3: Long-term memory
Part 4: Working memory
Lecture Learning Outcomes
Identify and explain the different components of the multi-store model of memory (sensory memory, short-term memory, and long-term memory).
Define working memory, characterize its components, and explain how it is different from short-term memory.
A Definition of Memory
Memory is a change in the brain or mind following an experience.
Yavin Dudai defines it as "The retention of experience-dependent internal representations over time."
It involves retaining, retrieving, and using information about stimuli, images, events, ideas, and skills after the original information is no longer present.
Research focuses on distinctions between different types of memory.
Different types of memory likely function in different ways.
Early Theories of Memory
William James distinguished between primary and secondary memory in the 19th century.
Primary memory: Current contents of consciousness.
Secondary memory: Mental representations of the distant past, not currently in consciousness, requiring retrieval.
Content-Based vs. Process-Based Theories of Memory
Content-based theories: Describe the different types of memory and their properties.
e.g., semantic memory for facts, episodic memory for experiences
Process-based theories: Describe the processes and algorithms for holding memories in the mind.
e.g., encoding vs. consolidation vs. storage vs. retrieval
e.g., the Temporal Context Model, pattern separation in the hippocampus, retrospective vs. prospective working memory, etc.
This lecture focuses on content-based theories.
The Many Types of Memory
Sensory Memory
Short-Term Memory
Working Memory
Long-Term Memory
Declarative Memory (Explicit Memory)
Events (Episodic Memory): Specific personal experiences from a particular time and place.
Facts (Semantic Memory): World knowledge, object knowledge, language knowledge, conceptual priming
Medial temporal lobe, middle diencephalon, and neocortex
Basal ganglia and cerebellum
Perceptual and association neocortex.
Skeletal muscle
Reflex pathways
The Multi-Store Model of Memory
Atkinson & Shiffrin (1968) proposed the multi-store model.
The model includes:
Sensory memory
Short-term memory
Long-term memory
Information flows from sensory memory to short-term memory via attention.
Information can be transferred from short-term memory to long-term memory via rehearsal.
Information can be retrieved from long-term memory back into short-term memory.
Sensory Memory
Sensory memory is a buffer that briefly holds all information arriving at our senses.
Characteristics:
Extremely large capacity
Extremely short timescale
Separate sensory memory store for each sense:
Vision: iconic memory (less than 1 second duration)
Audition (hearing): echoic memory (up to 10 seconds duration)
New information constantly overwrites old information.
Iconic Memory
Iconic memory is sensory memory for visual information.
Explains the persistence of vision, where new sensory information blends with existing information.
Examples include:
Sparkler's trail of light
Illusion of motion in films and zoetropes
Superpositions in thaumatropes
Echoic Memory
Echoic memory is sensory memory for auditory information.
Speech perception and conversation rely on echoic memory.
Example: Responding to a question after a delay because the information was briefly stored in echoic memory.
The Duration of Sensory Memory
Sperling (1960) investigated the duration of sensory memory.
Whole report: Participants reported as many letters as possible from a displayed array.
Average: 4.5 out of 12 letters (37.5%)
Partial report: Participants heard a tone indicating which row to report immediately after the array disappeared.
Average: 3.3 out of 4 letters (82.5%)
Delayed partial report: Tone presented after a delay.
Performance rapidly worsened as the delay increased.
Short-Term Memory
Short-term memory retains a limited amount of information for a limited time.
Characteristics:
Limited capacity
Short timescale (15-20 seconds without rehearsal)
Rehearsal can extend the duration of information in short-term memory.
Rehearsal is a conscious, effortful process.
What is the Duration of Short-Term Memory?
Peterson & Peterson (1959) measured the duration of short-term memory using a task where participants had to remember trigrams (e.g., TGH, SRD, CLS, GDA) after varying delay periods.
What is the Capacity of Short-Term Memory?
Digit span task measures capacity (Gilker, 1992).
Typical result: 5-9 items (Miller's law of 7 oldsym
pm 2).
What constitutes an 'item'?
Chunking
Small units can be combined into larger, meaningful units to increase storage capacity.
e.g., 0-4-1-7-2-1-0-0-2-2 vs. 0417-210-022
A chunk is a collection of strongly associated elements, weakly associated with other chunks.
Chunking is a skill that can be improved.
Ericcson et al. (1989) trained a student with average memory to use chunking.
S.F. initially had a digit span of 7.
After 230 1-hour sessions, S.F. could remember up to 79 digits by chunking.
Long-Term Memory
Long-term memory retains very large amounts of information for very long durations.
Information must be retrieved from long-term memory to be used.
Declarative and Non-Declarative Long-Term Memory
Declarative memory requires conscious effort for recall.
Information must be 'declared' to consciousness.
Also called explicit memory.
Subtypes: episodic and semantic memory.
Non-declarative memory can be recalled without effort.
Examples: Paris is the capital of France, your mother's name, dogs are furry.
Episodic memory: Memory for events.
Examples: What you did last New Year's Eve, your first kiss, what you ate for breakfast this morning.
Double Dissociations
Memory systems are often described in dichotomies.
Double dissociation is the gold standard in neuropsychology to confirm these are truly distinct systems.
Analogy: Some people are blind but not deaf, others are deaf but not blind, indicating independence of sight and hearing in the brain.
To show two memory systems are distinct, look for patients with a deficit in one system but not the other.
Double Dissociation: Episodic Memory and Semantic Memory
Patient K.C.
In 1983, K.C. had a motorbike accident.
Closed head injury with damage to the medial temporal lobe and hippocampus.
Severe anterograde amnesia and some retrograde amnesia for episodic memory.
No episodic memory: cannot relive past events.
Intact semantic memory: can remember general information and facts about the past.
Patient L.P. ('Italian woman')
Had severe encephalitis in 1984, damaging the left temporal lobe.
Impaired semantic memory but preserved episodic memory.
Working Memory (Versus Short-Term Memory)
Working memory is a limited-capacity system for temporary storage and manipulation of information for complex tasks (comprehension, learning, reasoning).
Distinction between short-term and working memory is subtle but important.
Short-term memory is a component of working memory.
Short-term memory holds information; working memory processes and manipulates it.
Short-term memory: Repeat the digits.
Working memory: Repeat the digits in reverse order.
A Model of Working Memory
Baddeley & Hitch (1974) proposed a model of working memory.
The phonological loop and visuospatial sketchpad are short-term memory stores with different coding types.
The central executive coordinates and manipulates information from these stores.
The Phonological Loop
Specialized for auditory and linguistic information (spoken words, written language, sounds).
Has a fixed duration.
Three sources of evidence:
The phonological similarity effect
Letters/words are most likely to be mistaken for similar-sounding ones.
Articulatory suppression
Repeating a separate word aloud interferes with working memory for verbal stimuli.
The word length effect
Memory is poorer for lists of long words than short words.
Long words take longer to rehearse; fewer fit in the loop's duration.
The Visuospatial Sketchpad
Stores visual and spatial information (pictures, objects, maps).
'Mental images' are retained in the sketchpad.
Evidence for mental imagery comes from studies of mental rotation.
The Central Executive
Controls the focus of attention.
Focusing, switching, dividing attention.
Suppresses irrelevant information.
Retrieves and manipulates information from other stores.