lecture 12 - Introduction to memory systems - memory joints Flashcards
1
Q
The “joints” of memory
A
“Carving nature at its joints” Plato
* Complex system needs classification to be
better understood and described
* Break complex system into components,
but try to do this in a natural, non-
arbitrary way
* Goal: Establish taxonomy of memory types
that make scientific sense
2
Q
how do we learn about memory
A
By thinking
about it, via
introspection
Via empirical
research and
theory-
building
Cycles: We consider
how findings from
different methods fit
together or contradict
and re-assess theories
continuously
3
Q
memory processes
A
- Encoding – entering information into
the system - Storage – holding information statically
- Retrieval – getting information out of
the system - Let’s apply these terms to a basic
model of memory, a starting point in
our taxonomy
4
Q
An information-Processing approach
A
- Intuitive; attributed to Broadbent
- Emphasizes memory as a system for internally preserving
information from the environment - Boxes represent permanent, universal structures. Processes that
control or act upon contents might be more flexible and variable. - Arrows represent how the information moves from one system to
another
environment —>(x2 arrows) sensory memory —-> (x2 arrows) short term memory —-> (x1 arrow) long term memory
5
Q
Environment
A
- Contains information that we might want to
know/preserve - It’s outside the memory system, but you could
consider this “storage” (O’Regan, 1992)
6
Q
Sensory memory
A
- Brief storage of information within a specific perceptual modality (e.g.,
audition, vision, etc.) - Very recent memories retain high sensory fidelity for a lot of
information, closely linked to perceptual systems - Processes: Information from environment encoded into sensory
memory
7
Q
Short-term memory
A
- Retention of small amounts of information over periods of a
few seconds - Processes: Some information stored in sensory memory is
encoded into short-term memory
8
Q
Long-term memory
A
- System(s) for holding information over long periods of time
- Some information stored in short-term memory is encoded into long-term
memory - When you need to use a piece of knowledge, you retrieve it
- Information loss
- Not all that is remembered briefly is transferred to long-term memory
9
Q
Why these distinctions?
A
- Our goal: assess these distinctions to figure out what we think of
these distinctions. Are these memory’s natural “joints”? - Today: let’s consider short-term and long-term memory
- Evidence that time retained might define a natural “joint” in the
memory system comes from amnesia case
10
Q
Henry Molaison (HM)
A
Had surgery removing medial temporal lobes to treat severe epilepsy
- After surgery meant to treat epilepsy, HM lost:
- Some long-term memories
- Memory strategies did not help
- Ability to retain new memories (beyond immediately)
- Aspects of HM’s cognition that were spared:
- Most sensory functions
- Normal overall IQ (some components of test were
affected) - Conversations (debateable)
- Selective attention
- Immediate memory (unless he was distracted)
- Procedural memory
- Importance of case: dissociates some kinds of
memory from others
11
Q
Dissociation
But is this
dissociation really to do with time?
A
- HM could think: he could hold a
conversation, he could briefly remember
novel information and briefly use it, he
could control what he did - He could remember information for
periods of seconds (short-term
memory?) - HM could not explicitly learn new
information, or retrieve long-term
memories formed over several years prior
to his surgery (long-term memory) - This represents a dissociation between STM
and LTM - Damage to medial temporal lobe affects (some)
long-term but not short-term memory - Double dissociation occurs if a different
variable affects memory at short term only
12
Q
HM’s deficits dissociation proposed
A
Some evidence shows that patients with similar amnesia can encode new memories, and
can remember them for long periods as long as they do nothing in between learning and
testing (Cowan, Beschin, & della Sala, 2004)
How can we distinguish between failed storage of LTM, versus failed retrieval from LTM?
* Possible to “forget” but recall later?
* Consider superior autobiographical memory
issues between STM AND LTM
13
Q
Why this information processing
scheme cannot be right
A
- It certainly isn’t complete
- Testing it: can we isolate sensory, short-
term, or long-term memory in a test? - Short-term memory is usually
tested with serial recall of a novel
verbal list. - Patients like HM can recall these
lists. - But what about more novel
information?
14
Q
Can we isolate STM or LTM in a single test?
A
- Most memory tests focus on verbal information
- Why?
- Would that isolate short-term memory?
- The amnesic patients with medial-
temporal lobe damage (red lines) in
these reports were tested on
memory for novel visual objects - Clear deficits even at short delays
- Conclusion: maybe ”short-term”
memory is not normal in these
From Ranganath & Blumenfeld, 2005
patients after al
graphs in notes
15
Q
Simple information-processing
scheme is not right
A
- It is incomplete at best
- What about the “procedural” memory that
HM was quite good at? Isn’t that “long-
term”? - Patients with medial-temporal lobe
lesions fail visual short-term memory
tests - Could mean that additional “joints”
needed in short-term memory - Could mean that thinking about
memory in terms of time is not a good
“joint”
16
Q
what is memory
A
- Schacter (2001) described the 7 sins of memory and accepts the sins are the necessary consequences of the virtues that make our memories rich and flexible.
- We are good at coping with forgetting by using knowledge to reconstruct partial memories
- Our falliable memories play an crucial part in our ability to function independently in our complex world
Clive wearing has much of his memory capacity destroyed by diease
17
Q
Why do we need memory?
A
- Clive wearing = talented musician, master of a major london choir, singer and asked to sing for pope in papal visit to london. 1985 got brain infection from herpes simplex virus that caused encephalitis and inflammation of the brain that can be fatal. When he recovered consciousness he was amnesic and was unable to store info for periods longer than seconds. His interpretation was that he had just discovered consciousness and would announce that to any visitor and write it in his notebook each time crossing out the previous line and writing “I have now recovered consciousness” or “consciousness has now finally been recovered,” an activity that continued for many, many years.
- Clive knew who he was and could about his early life but in little detail. He knew he went to cambridge uni for 4 years but could not recognise a photo of his college.
- He could remember, although somewhat vaguely, important events in his life such as directing and conducting the first modern performance of Handel’s Messiah using original instruments in an appropriate period setting, and could talk intelligently about the historical development of the role of the musical conductor. However, even this selected knowledge was sketchy; he had written a book on the early composer Lassus, but could not recall any of the content. Asked who had written Romeo and Juliet, Clive did not know. He had remarried, but could not remember this. However, he did greet his new wife with enormous enthusiasm every time she appeared, even though she might only have been out of the room for a few minutes; every time declaring that he had just recovered consciousness.
- He was incapacitated by his amnesia - he could not read a book or follow a tv show because he forgot what had happened before. If he left his hospital room he was lost.
- He was locked into a permanent present, something he described as “hell on earth.” “It’s like being dead—all the bloody time!”
- His memory of music was unimpaired, he could conduct his choir and could read a score of a song and play the keyboard and sing.
For a brief moment he appeared to return to his old self, only to feel wretched when he stopped playing. Over 20 years later, Clive is still just as densely amnesic but now appears to have come to terms with his terrible affliction and is calmer and less distressed.
18
Q
One memory or many?
A
- Clive had damage to a range of brain areas so had problems beyond his amnesia
- The fact clives musical memory and skills are unimpaired suggests memory is not a single simple system.
- Other studies have shown that densely amnesic patients can repeat back a telephone number, suggesting preserved immediate memory, and that they can learn motor skills at a normal rate.
- Amnesic patients are capable of a number of types of learning, demonstrating this by improved performance, even though they do not remember the learning experience and typicay deny having encountered the situation before.
The evidence suggests that rather than a single global memory system, the picture is more complex
19
Q
Theories, maps and models
A
- In 1950s many people though theories should look like theories from physics
- Clark Hull studied the learning behaviour of white rats and used the results to develop a general theory of learning to predict learning behavior in both rats and humans using postulates and equations inspired by Newton’s work (Hull, 1943).
- Hull’s great rival, Tolman (1948) thought of rats as forming ‘cognitive maps’ internal representations of their environment that were acquired as a result of active exploration.
- The controversy rumbled on from the 1930s to the 1950s, and then was abandoned quite suddenly. Both sides found that they had to assume some kind of representation that went beyond the simple association between stimuli impinging on the rat and its learned behavior, but neither seemed to have a solution to the problem of how these could be investigated.
- Broad view of theory = theories are essentially like maps - they summarise our knowledge in a simple and structured way that helps us to understand what is known.
- A good theory helps us ask new questions and that helps us find out more about the topic we are mapping.The nature of the theory will depend on the questions we want to answer
- In the case of psychological theories, different theories will operate at different levels of explanation and focus on different issues.
Reductionism - the view that all scientific explanations hsould aim to be based on a lower level of analysis. Psychology in terms of physiology, physiology in terms of chemistry, and chemistry in terms of physics.
20
Q
How can we study memory?
A
- The attempt to understand human memory extends at least as far back as Aristotle, and forms one of the classic questions within the philosophy of mind, although without reaching any firm conclusions.
- Limitation of a purely philosophical approach to the understanding of memory in particular and the mind in general = its reliance on introspection the capcity to reflect and report our ongoing thoughts. These are not unimportant but are not a reliable indication of the way our minds work, for two principal reasons.
- 1 -people differ in what they appear to experience in a given situation; does memory depend on visual imagery, and if not, why do some of us experience it?
- 2 - we are only consciously aware of a relatively small proportion of the mechanisms underpinning our mental life
- While there are still important issues addressed by the philosophy of mind, it is now generally acknowledged these can best be pursued in collaboration with a scientific approach based on empirical evidence.
- Sir Francis Galton found that ‘eminent men’ descriptions of the vividness of their memories after being asked to reflect on their breakfast tavle from that morning varied widely, but this did not affect their accuracy, suggesting a nonconscious process at play. This raises questions about whether people experience memory differently or simply describe it differently. The challenge is to move beyond introspection to better understand memory system
- An answer to this started to develop in Germany in the latter half of the 19th century. It was concerned initially with the discipline of psychophysics, an attempt to systematically map the relationship between physical stimuli such as brightness and loudness onto their perceived magnitude.
- Despite success in linking physical stimuli to the psychological experience of participants, capacities such as learning and memory were initially regarded as unsuitable for experimental study.
- This view was dramatically overturned by a German philosopher Herman Ebbinghaus who conducted an intensive series of experiments on himself over a two year period, showing that it was indeed possible to plot systematic relationships between the conditions of learning and the amount learned. Having published this, the first classic book on the science of memory (Ebbinghaus, 1885), he moved on to study color vision, intelligence, and a range of other questions in the newly developing field of experimental psychology.
- Ebbinghaus started by making the experimental situation simpler, creating material that had no meaning but could be learned and reported verbally. He invented nonsense syllables, which are consonant-vowel-consonant nonwords like zug, pij, and tev. He used himself as the subject, keeping the room, time of day, and fast presentation consistent to prevent finding meaning in the stimuli. Ebbinghaus established key learning principles and the classic forgetting curve, forming the basis for further work in this field.
- The Ebbinghaus tradition developed mainly in the US, focusing on how new learning interacted with existing knowledge. Results were seen as associations between stimuli and responses, often using nonsense syllables. This verbal learning approach grew from the 1930s to the 1960s, leading to the creation of The Journal of Verbal Learning and Verbal Behavior, which later became The Journal of Memory and Language.
Verbal learning - a term applied to an approach to memory that relies principally on the learning of lists of words and nonsense syllables
21
Q
how many kinds of memory
A
- Shift from Single to Multiple Memory Systems
Early psychology emphasized a single memory system based on stimulus–response associations.
Cognitive psychology reframed memory as involving multiple systems:
➤ Sensory memory
➤ Short-term memory (STM)
➤ Long-term memory (LTM) - The Modal Model (Atkinson & Shiffrin, 1968)
Became a widely accepted model of memory in the 1960s.
Known as the modal model because it represented the dominant view of the time.
Core structure:
Environmental input enters sensory memory
Information passes to short-term memory
Some of this is encoded into long-term memory
Figure 1.2 (referenced in the text) shows this linear flow model of memory.
3. Challenges to the Modal Model
Critics argued “memory stores” are too static.
Alternative view: unitary memory system driven by common processes (e.g., Nairne, 1990, 2002).
Observations of task similarities across memory types suggest shared mechanisms.
Authors’ stance:
Both structures (stores) and processes (e.g., encoding, retrieval) matter.
Analogy: Just like brain research requires both anatomy and physiology, memory research needs both static and dynamic perspectives.
4. Bidirectional Flow of Information
The modal model implies one-way flow (environment → STM → LTM).
But research shows information flows both ways:
LTM influences attention and perception.
Our existing knowledge shapes what we notice and remember.
Example:
A football fan watching a match perceives and remembers specific plays more accurately than someone unfamiliar with the sport.
5. Memory System Components
Memory Type Description
Sensory Memory Interface between perception and memory. Short-lived, high capacity.
Short-Term Memory Temporary holding system for small amounts of info.
Long-Term Memory Durable store of knowledge and past experiences.
Each system is subdivided further (e.g., working memory is a form of STM).
Not just sequential—components interact and influence one another.
6. Structure of the Book
Begins with sensory memory (briefly, as it’s closer to perception than memory).
Moves to short-term & working memory.
Ends with a preliminary look at long-term memory
22
Q
sensory memory
A
🔥 1. Sparkler Effect: Perception of Visual Continuity
Moving a sparkler in a dark room leaves a fading visual trail.
Suggests brief visual storage—a form of memory allowing continuity.
Movies rely on this: static frames + brief gaps = perceived motion due to visual persistence.
👁️ 2. Iconic Memory (Visual Sensory Memory)
📌 Definition:
Coined by Neisser (1967)—stores visual information very briefly.
Basis for the illusion of continuity in vision.
🧪 Sperling’s Experiments (1960, 1963):
Task Observation
12-letter grid shown briefly Participants could recall only 4–5 items.
Partial report technique (cue tone after display) Participants likely encoded more than they could report.
Recall depends on cue delay Longer delay = worse recall → info fades quickly.
💡 Masking Effects (Sperling, 1963; Turvey, 1973):
Type Mechanism Stage of Processing
Brightness masking Light disrupts trace; stronger with same eye → early, retinal level
Pattern masking Similar visual patterns overwrite info; works across eyes → later visual processing
🔄 These forms of interference demonstrate how fragile and short-lived iconic memory is.
🎯 Function of Iconic Memory:
Helps process the complex visual environment.
Acts as a buffer to build a coherent scene before detailed processing.
Bridges perceptual gaps—e.g., why we see films as continuous rather than a sequence of frames.
🔊 3. Echoic Memory (Auditory Sensory Memory)
📌 Definition:
Also coined by Neisser (1967).
Stores brief auditory information for a short duration.
🧪 Auditory Serial Recall (Murdock, 1967):
Presentation Error Pattern
Visual Errors increase toward the end of the list.
Auditory Recency effect: last 1–2 items are remembered better.
Disrupting with a spoken suffix (e.g., “recall”) removes the recency effect.
Non-speech sounds (e.g., buzzer) do not disrupt recall.
📦 Crowder & Morton (1969): Precategorical Acoustic Store
Echoic memory = a buffer before sounds are processed for meaning.
Effectiveness depends on suffix type—supports a sensory (not semantic) mechanism.
⚖️ Controversy: Memory vs. Perception?
Viewpoint Argument
Memory view Echoic memory is a temporary auditory store aiding recall.
Perception view Effects may arise from ongoing speech perception, not memory storage.
📚 Ongoing debate: is echoic memory best understood as memory or as a perceptual mechanism?
🧩 Key Implications:
Iconic and echoic memory help bridge gaps in sensory input.
Serve as entry points to short-term memory.
Understanding these systems is essential to models of perception and memory
23
Q
short term and working memory
A
📦 1. Short-Term Memory (STM)
✅ Definition:
Theory-neutral term.
Refers to temporary storage of small amounts of information over brief periods.
🧠 Key Features:
Not tied to a specific mechanism—leaves open how storage occurs.
STM tasks often involve long-term memory (LTM) support (e.g., chunking, familiarity).
Commonly studied using verbal materials, but also relevant for:
Visual & spatial info ✅
Smell & touch ❌ (less studied)
🔄 Rehearsal:
Verbal rehearsal often used, even with non-verbal stimuli, to maintain performance.
🧰 2. Working Memory (WM)
✅ Definition:
A system for temporary storage & manipulation of information.
Essential for complex cognitive tasks like:
Reasoning
Learning
Comprehension
🧩 Key Assumptions:
Provides a mental workspace.
Tightly linked to attention.
Draws from both STM and LTM resources.
🧠 3. Theoretical Models of WM
Feature Description
Diverse models Theorists tailor models to their research interests.
Common assumption WM integrates memory and attention mechanisms.
Some models emphasize attention over memory.
🧠 4. Baddeley & Hitch’s Multicomponent Model (1974)
🔍 Purpose:
To bridge psychological and neuropsychological research on STM.
To explain WM’s role in real-world cognition (e.g., problem-solving, comprehension).
🏗️ Impact:
Remains highly influential over decades (updated by Baddeley, 2007).
Forms the core focus of Chapter 4.
📚 Summary Table
Concept STM WM
Focus Passive storage Active maintenance + manipulation
Duration Brief Brief, but task-dependent
Contents Small amounts of info Task-relevant info (verbal, visual, spatial)
Associated with Memory Memory + Attention
Key Model Varies Baddeley & Hitch (1974) Multicomponent Mode
24
Q
long-term memory
A
We shall use the classification of long-term memory proposed by Squire (1992). As shown in Figure 1.6, this classification makes a broad distinction between explicit or declarative memory and implicit or nondeclarative memory. Explicit memory refers to situations that we would generally think of as involving memory, both for specific events, such as meeting a friend unexpectedly on holiday last year, and remembering facts or information about the world, for example the meaning of the word testify or the color of a ripe banana. Implicit memory refers to situations in which some form of learning has occurred, but which is reflected in performance rather than through overt remembering, riding a bicycle for example or reading a friend’s handwriting more easily because we have encountered it frequently in the past
25
explicit memory
made up of semantic and episodic memory
🧠 Semantic vs. Episodic Memory
(Based on Tulving's 1972–2002 framework)
📂 1. Two Major Categories of Long-Term Memory
(As shown in Figure 1.6 – implied)
Memory Type Description
Semantic Memory General knowledge about the world (facts, concepts, meanings, schemas).
Episodic Memory Memory for specific events and experiences tied to a particular time and place.
📘 2. Semantic Memory
✅ Definition:
Knowledge of the world, concepts, and language.
Includes:
Word meanings
Sensory attributes (e.g., color of lemons, taste of apples)
Social scripts (e.g., what to do at a restaurant)
🧠 Features:
Generalized knowledge.
May be learned from a single event, even if the event details are forgotten.
Example: Hearing a friend has died contributes to semantic memory about them, even if you forget when you heard it.
🧠 3. Episodic Memory
✅ Definition:
Memory for unique personal experiences, with contextual details (time/place/emotion).
🕰️ Tulving’s Concept of "Mental Time Travel":
The capacity to re-live past experiences.
Enables use of past experiences for future planning (e.g., remembering your emotional reaction → sending a condolence letter).
🚫 Clinical Note:
Episodic memory is severely impaired in amnesic patients, e.g., Clive Wearing, who lives in a near-constant present.
🔄 4. Relationship Between Semantic & Episodic Memory
📌 Two Theoretical Views:
Viewpoint Description
Semantic memory as a residue of multiple episodes Repeated episodic experiences (e.g., learning that Madrid is the capital) build semantic knowledge.
Separate systems vs. shared system Ongoing debate: Tulving argues for separate storage systems; Baddeley suggests different retrieval routes to a common store.
🧠 Supporting Evidence:
Amnesic patients often struggle to form new semantic knowledge, suggesting episodic memory may support semantic learning.
📚 Summary Table
Feature Semantic Memory Episodic Memory
Type of knowledge General/world knowledge Specific personal experiences
Context Decontextualized Time/place-specific
Examples "Madrid is the capital of Spain" "I visited Madrid in 2018"
Acquisition From repeated exposure or a single event Single-trial learning
Clinical relevance Often preserved in amnesia Often impaired in amnesia
Tulving's 2002 emphasis Static knowledge Mental time travel (re-experiencing)
26
implicit memory
🧠 Implicit (Nondeclarative) Memory in Amnesic Patients
🚫 1. Amnesia and Explicit Memory Deficits
Amnesic patients show:
Severe impairment in episodic memory
Reduced ability to form new semantic memories
But some learning abilities are preserved, which led to the development of the concept of implicit memory.
✅ 2. Preserved Learning in Amnesia
Type of Learning Example Description
Classical Conditioning Tone + air puff → eye blink (Weiskrantz & Warrington, 1979) Patients learn to blink in anticipation, but cannot recall the experience.
Motor Skill Learning Tracking a moving target with a stylus (Brooks & Baddeley, 1976) Skill improves with practice despite no memory of the task.
Word Completion Priming Shown "bring" → later given "BR–" Patients "guess" previously seen words without realizing it (Warrington & Weiskrantz, 1968).
Perceptual/Motor Tasks Mirror reading, jigsaw puzzles (Cohen & Squire, 1980) Progressive improvement despite no conscious memory of having done it before.
✨ 3. Key Concept: Priming
Definition: Prior exposure to a stimulus facilitates future responses without conscious awareness.
Demonstrates that something is stored, even if it is not accessible through explicit recall.
Found across modalities (visual, auditory, motor).
🧬 4. Multiple Implicit Memory Systems?
🧠 Two Competing Views:
View Description
Single-system theory All implicit memory types stem from one system (Neath & Surprenant, 2003).
Multiple-systems view Different tasks (e.g., priming, motor learning, conditioning) rely on distinct brain systems, evolved for different functions (Brooks, Baddeley, Squire, etc.).
Authors favor the multiple-systems view:
Despite shared features, these learning forms involve different neural mechanisms.
Evolution may have used similar learning principles in distinct systems.
🧠 Summary Table
Feature Explicit Memory Implicit Memory
Requires conscious recall? Yes No
Impaired in amnesia? Yes No (mostly preserved)
Examples Remembering a word list, facts, events Conditioning, motor learning, word priming
Associated brain areas Hippocampus, medial temporal lobe Basal ganglia, cerebellum, neocortex (varies by task)
Tested by Free recall, recognition //Skill tasks, word stems, reaction time
27
memory - beyond the lab
📚 Applying Memory Theory in the Real World – Study Summary
🧠 1. From Lab to Life
Theories of memory (encoding, storage, retrieval) are often developed under controlled lab conditions.
But for these theories to be truly useful, they must explain how memory works in real-world contexts (e.g., children, elderly, different cultures, patients).
⚖️ 2. Lab vs. Everyday Memory Debate
Some psychologists argue for lab-only research for control and clarity.
Others (e.g., Bartlett) stress the need to study memory in natural settings to avoid missing important aspects.
This debate gained attention at the 1978 Practical Aspects of Memory Conference, inspired by concerns that real-life memory was being neglected.
🗣️ 3. Neisser’s Critique
Ulric Neisser criticized the narrow lab focus:
“If X is a socially significant aspect of memory, psychologists have hardly ever studied X!”
His critique sparked debate but highlighted the need for balance between lab and real-world memory research.
🤝 4. Theory and Application: Allies, Not Rivals
Real-world studies have:
Tested and refined theories
Shaped practical tools (e.g., memory rehabilitation, clinical assessments)
Informed about episodic memory’s role in daily life (e.g., amnesia research)
🌍 5. Real-World Drivers of Theory
Semantic Memory: Sparked by AI and language processing needs.
Eyewitness Testimony: Highlighted memory limits in legal settings (Loftus, 1979).
Prospective Memory: Remembering to do things—crucial yet understudied due to its complexity.
✅ 6. Key Takeaway
Theoretical and practical approaches complement each other.
Real-world studies enrich theory, and theory guides practical solutions to memory-related problems
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the contribution of neuroscience
Both the Ebbinghaus and Bartlett approaches to the study of memory were based on the psychological study of memory performance in normal individuals. In recent years, however, this approach has increasingly been enriched by data from neuroscience, looking at the contribution of the brain to our capacity to learn and remember. Throughout this book, you will come across cases in which the study of memory disorders in patients has thrown light on the normal functioning of human memory. In particular, the problems faced by patients with memory problems can often tell us about the function that our memories serve, and how they can be further investigated. Recent years have seen a rapid development of methods that allow the neuroscientist to observe and record the operation of the brain in healthy people both at rest and while performing complex activities, including those involved in learning and remembering.
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neuropsychological approaches
🧠 Neuropsychological Studies of Memory – Study Summary
⚙️ 1. Brain Damage and Memory
Memory issues often follow brain damage, with the location and cause influencing the type of impairment.
Understanding these patterns helps in both treatment and theory development.
👥 2. Group Studies
Involves patients with shared causes (e.g., traumatic brain injury).
Useful for clinical insight but theoretically unclear due to mixed deficits (e.g., memory and attention problems).
🍷 3. Selective Disorders – Korsakoff’s Syndrome
Caused by alcohol abuse + poor nutrition.
Memory deficits are strong but not always isolated, making theoretical conclusions still somewhat unclear.
🔍 4. Single Case Studies – e.g., HM
Most valuable when damage affects only one function, such as episodic memory, while other functions remain intact.
HM (Henry Molaison) showed preserved STM but impaired LTM, proving episodic memory can be isolated — a dissociation.
🔁 5. Double Dissociations
Even more powerful: one patient has intact STM + impaired LTM, another the opposite.
E.g., Shallice & Warrington (1970) found patients with normal LTM but severely impaired STM — supports idea of separate systems.
Double dissociations are rare but highly compelling for theory.
🔗 6. Limits of Dissociation
As memory models get more complex (3+ components), triple or quadruple dissociations become impractical.
Instead, researchers use converging operations:
Multiple methods and participant types focused on the same question to find the most consistent explanation.
🧪 7. Practical Limits in Neuropsychology
Rare to find “pure” patients.
Requires skilled neuropsychologists and hard-to-access patient populations.
Growth in memory research is now driven more by studies of healthy brains using modern tools (e.g., fMRI, EEG).
✅ Key Takeaway
Case studies of brain damage (especially dissociations) have shaped memory theory,
but due to limits, researchers now rely on multiple methods (converging operations) to test complex models
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observing the brain - structural imaging
For many years, what we knew about the brain’s structure came only from examining brains after death. This changed dramatically with the development of CT scans (Computerised Tomography). CT uses X-rays taken from multiple angles around the head to generate a 3D image of the brain. While this method is still useful in clinical settings (like hospitals), it has largely been replaced in research by a more advanced and safer technique: MRI (Magnetic Resonance Imaging).
MRI works very differently from CT. It doesn’t use radiation; instead, it places the person’s head inside a strong magnetic field. Short pulses of radio waves are sent into the brain, and when the field is turned off, the brain releases energy it had absorbed. This released energy varies depending on the type of brain tissue, allowing the scanner to produce a detailed three-dimensional image. MRI can distinguish between gray matter (which contains neuron cell bodies), white matter (the axons that link different brain regions), and cerebrospinal fluid (which cushions the brain and carries waste).
The clarity of MRI images depends on the strength of the magnetic field—most clinical MRI machines have a strength of 3 Tesla, but even higher-powered machines (like 7 Tesla) are now used in research, offering extremely fine spatial detail.
A major advantage of MRI over CT is that it provides much more detailed images and does not expose patients to any radiation. It’s also highly adaptable. By changing the frequency of the radio pulses, MRI can highlight different parts of brain structure—for example, making gray matter more visible in one scan and white matter in another.
A newer and increasingly important development in MRI technology is Diffusion Tensor Imaging (DTI). This method allows scientists to visualize the pathways of white matter in the brain. White matter fibers are wrapped in a fatty substance called myelin, which causes water inside them to flow in a particular direction. DTI tracks this movement, letting researchers map the fiber bundles that carry information between brain regions—a technique also known as tractography. This has been particularly useful in understanding how different parts of the brain communicate and coordinate during memory processing
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functional imaging - observing the working brain
While imaging the structure of the brain is obviously important and helpful, from the viewpoint of a psychologist it is much more valuable to be able to observe the brain in action and to relate this to the ongoing mental activity of the participant. Some of the earlier developments here resulted from implanting electrodes in the brains of animals, a method that is clearly of limited application to humans. Exceptions do occur, however; for example, when patients are undergoing brain surgery to treat intractable epilepsy. The brain itself does not contain pain receptors, and so the patient can remain conscious and report their experiences when different areas are stimulated. Of particular relevance to memory are studies involving the hippocampus. Early reports that this occasionally evoked specific and verifiable episodic memories have proved difficult to replicate; however, recent work suggests that such stimulation may evoke a feeling of déjà vu, a sense of familiarity when confronted with a quite novel complex stimulus event such as hearing someone playing a trumpet. Such an experience could have been interpreted by the patient as a genuine memory (Gloor, 1990; Vignal, Maillard, McGonigal, & Chauvel, 2007).
In addition to stimulation, implanted electrodes can be used to record from single cells, a procedure that is proving promising (Rutishauser, Schuman, & Mamelak, 2008). Although recording from implanted electrodes is giving exciting new data, its use is, of course, limited by the fact that it can only ethically be used in a very limited number of patients and is confined to brain areas that are directly relevant to treatment
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transcranial magnetic stimulation TMS
A rather less invasive method of influencing the brain is offered by this method, in which a current is passed through a set of coils held close to the participant’s head. This results in a magnetic field which can polarize or depolarize the underlying brain tissue, causing a temporary, hence reversible “lesion” that can then provide evidence for the importance of that area of the brain in the observed cognitive activities. Transcranial magnetic stimulation (TMS) can be delivered either as a single pulse at precise point in processing, for example before stimulus presentation, or used repeatedly, leading to a disruption of that brain area that can last for many minutes. It has the advantage that it allows the experimenter to control the situation, comparing performance with and without stimulation, in contrast to the brain observation studies we will discuss next. In such cases, unlike TMS, the investigator may observe that a particular area of the brain is activated during a specific task, but that does mean that it is essential for that task. TMS, like neuropsychological lesion studies, is able to go beyond this basic correlation between area and task and demonstrate that without this brain area, the task cannot be performed.
Limitations of TMS are that currently it tends to affect a relatively large area with its influence typically limited to areas near the surface of the brain. Furthermore, while in general safe, it can result in discomfort, and occasionally even seizure in susceptible patients. Nevertheless, as methods develop it is likely to continue to play an important role in cognitive neuroscience (see Widhalm & Rose, 2019 for a recent overview)
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transcranial direct current stimulation tDCS
Transcranial direct current stimulation (tDCS) is a procedure whereby a low direct current is delivered via electrodes on the skull to selected areas, resulting in a flow of current through the selected area of the brain which may increase or decrease the neuronal excitability of the area stimulated. Anodal stimulation with a positive voltage increases neuronal excitability, cathodal stimulation with a negative voltage reduces neuronal excitability, while sham stimulation which emits a brief initial current that remains off for the remainder of the stimulation time may be used as a control condition. There is some evidence that it may reduce depression (Mutz et al., 2019), and a number of studies have claimed that it may be used for cognitive enhancement (Chill, Fitzgerald, & Hoy, 2016), although the evidence from this has been questioned (Horvath, Forte, & Carter, 2015). This approach has not currently had a major effect on our understanding of human memory.
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Electro-encephalography (EEG)
Electroencephalography (EEG) is a noninvasive technique used to measure the brain’s electrical activity. It involves placing electrodes on the scalp to detect the brain's fluctuating electrical signals, which can vary from a few to over 70 cycles per second. EEG is widely used in clinical settings, especially to detect epileptic seizures and to monitor sleep stages, each of which has distinct electrical frequency patterns.
In cognitive research, EEG is valuable for studying memory and thought processes. For example, it can distinguish between brain patterns when someone is recollecting an experience versus just finding something familiar. However, EEG captures the overall activity of the brain, making it difficult to pinpoint exactly which brain region is responsible for a specific task.
The main strength of EEG is its temporal resolution—it can detect changes in brain activity within milliseconds. This is especially useful when studying the brain's real-time response to a stimulus using Event-Related Potentials (ERPs). ERPs are extracted by aligning EEG signals to specific events (like the appearance of a word or sound) and averaging the responses over many repetitions to reveal the brain's reaction to that event.
Although ERPs are weak signals buried within the broader EEG, averaging helps isolate them. While ERPs don’t offer high precision in localizing brain areas, they can identify broad regions involved and how their activity changes over time, helping to map out the stages of cognitive processing during tasks.
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Magneto-encephalography (MEG)
While EEG and ERP signals reflect the variation in electrical voltage on the surface of the brain, such activity can also be detected by associated changes in magnetic activity using a technique known as magneto-encephalography (MEG). This also uses a range of detectors around the head. It differs from ERP in being most sensitive to activity in the sulci, the valleys within the folds of the brain, whereas ERP is more sensitive to the peaks or gyri. MEG signals are less subject to distortion from passing through the skull and the electrodes than is the case with ERP. It gives a less complex pattern than ERP, and potentially offers a more precise localisation of its origin within the brain. Although substantially more expensive than ERP, these advantages are resulting in the increasingly wide use of MEG
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blood flow based measures
Both ERP and MEG measures have good temporal resolution; they allow the tracking of brain activity over periods ranging from milliseconds to seconds, but have poor spatial resolution; it is unclear where the activity originates within the brain. Much more precise localization is possible by using methods that rely on the assumption that when a particular area of the brain is active, this is reflected in its metabolism, usually measured in terms of the amount of oxygen being used by that area
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Positron emission tomography (PET)
PET involves injecting a radioactive tracer into the bloodstream, which accumulates in areas of the brain with more activity. Detectors around the head pick up radiation to locate these active areas. Although PET was a significant tool in early functional imaging, it has poor temporal resolution, is invasive due to the use of radioactive substances, and is costly since it requires a cyclotron. As a result, it has been largely replaced by fMRI.
fMRI, on the other hand, measures changes in blood oxygen levels as an indicator of brain activity. Areas of the brain that are more active consume more oxygen, which alters the magnetic resonance signal of the hemoglobin carrying the oxygen. fMRI provides better spatial resolution than PET and is non-invasive, but it has poor temporal resolution (responses are delayed by several seconds). It is also expensive and time-consuming, making replication of studies difficult. The analysis of fMRI data involves comparing task conditions (e.g., remembering digits vs. seeing digits) to identify brain areas activated during specific cognitive tasks. This comparison relies on choosing a proper baseline and statistical methods to interpret activation patterns, which can be challenging and may vary between researchers.
In summary, while both methods have their advantages and drawbacks, fMRI has become the preferred tool for functional imaging, especially in the study of human memory, despite its limitations in terms of cost, time, and analysis complexity
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Multi-voxel pattern analysis (MVPA
multi-voxel pattern analysis (MVPA), an advanced technique developed to address limitations in traditional fMRI analysis. In standard fMRI, brain scans are divided into small areas called voxels, which are analyzed independently, potentially overlooking patterns of brain activity across multiple regions. MVPA, however, uses machine learning to detect patterns of activity that occur across multiple voxels when the same event is repeated. This method can reduce experimenter bias, set significance levels in advance, and classify brain responses to specific stimuli, like faces or houses.
MVPA has been dubbed "mind reading" due to its ability to predict what a person is thinking based on brain patterns. Some commercial companies even claim to use this for lie detection. However, it is crucial to understand that the technique doesn't detect lying directly, but rather the cognitive and emotional processes tied to it. In a real-world court case, the method's validity and accuracy were questioned, and it was not accepted as reliable evidence due to a lack of scientific consensus and real-world testing
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the cellular basis of memory
This is a huge and highly active field, but one that has so far had relatively little impact on the analysis of memory at a cognitive level. Classic work by the Nobel Prize Laureate Eric Kandel used a very simple animal Aplysia, a sea slug, to analyze two basic types of learning, habituation and sensitization. Habituation was studied by repeatedly touching the animal’s syphon; this resulted in withdrawal of its gill, a response that decreased systematically over repeated stimulation. The opposite effect, sensitization, occurred when touch was linked to the delivery of shock to the animal’s tail, a basic form of classical conditioning as originally demonstrated by Pavlov with dogs. Repeated presentation of the touch-shock pairing can be shown to lead to gene expression, new protein synthesis, and the development of new synaptic connections, all of which are associated with the long-term retention of the enhanced response to touch.
Further research in this area has identified two potential mechanisms of learning, long-term potentiation (LTP) and long-term depression (LTD), and whose mechanisms have been extensively studied at the molecular level, implicating neurotransmitter systems and genes. While this level of biological analysis is likely in the future to have clear implications for the understanding of memory at the cognitive level, and vice versa
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genetic approaches
the development of behavioral genetics, a field first focused on by Sir Francis Galton, who noticed that talents often ran in families, such as in the Bach family with music. While he acknowledged that family environment and social status also played a role, he pointed out that twins provided a unique opportunity to separate genetic influences from environmental ones. Twin studies compare identical twins (who share 100% of their genes) with fraternal twins (who share 50%), with the goal of understanding how much behavior is influenced by genetics versus the environment. Studies of separated twins are especially valuable for this.
The field has been complicated by associations with eugenics, particularly the Victorian fear of intelligent decline due to larger families among the less educated. This concern has been debunked by the Flynn effect, which shows that intelligence has been steadily increasing across generations. The Nazis misused eugenics to promote a false racial ideal, leading to horrific consequences. In the U.S., similar concerns have been raised about racial differences in intelligence, though such differences are largely due to varying environments.
Since the discovery of the human genome by Crick and Watson, interest in genetics has grown, particularly in the genetic basis of behavior. Some diseases, like Huntington's Disease and Down syndrome, have clear genetic links, but many diseases, like Alzheimer's, are less directly tied to genes. Research into gene-environment interactions (epigenetics) has become a major focus, but it’s clear that most complex behaviors depend on multiple genes and their interaction with the environment. This area is still developing and holds significant promise for future research
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summary of chapter 1
Although we complain about our memories, they are remarkably efficient and flexible in storing the information we need and discarding what is less important.
* Many of our memory lapses result from this important need to forget nonessentials, if we are to remember efficiently.
* The study of memory began with Ebbinghaus, who greatly simplified the experimental situation, creating a carefully constrained approach that continued in North America into the 20th century.
* Alternative traditions developed in Germany, where the study of perception influenced the way in which Gestalt psychologists thought about memory, and in Britain, where Bartlett used a richer and more open approach to memory.
* During the 1950s and 1960s, these ideas, influenced further by the development of the computer, resulted in an approach that became known as cognitive psychology.
* In the case of memory, this emphasized the need to distinguish between encoding or input into memory, memory storage, and memory retrieval, and to the proposal to divide memory into three broad types, sensory memory, short-term memory, and long-term memory.
* The information-processing model is very well illustrated in Sperling’s model of visual sensory memory, in which the various stages were ingeniously separated and analyzed.
* These were assumed to lead into a temporary short-term or working memory. This was initially thought to be largely verbal in nature but other modalities were subsequently shown to be capable of temporary storage.
* The short-term memory system was assumed to feed information into and out of long-term memory.
* Long-term memory was further subdivided into explicit or declarative memory, and implicit or nondeclarative memory.
* Explicit memory was further divided into two types: The capacity to recollect individual experiences, allowing “mental time travel,” became known as episodic memory, whereas our stored knowledge of the world was termed semantic memory.
* A range of implicit or nondeclarative learning and memory systems were identified, including classical conditioning, the acquisition of motor skills, and various types of priming.
* An important development in recent years has been the increased interest in extending theory beyond the laboratory.
* However, this has led to controversy—it is clear that we need the laboratory to refine and develop our theories, but that we also need to move outside the laboratory to investigate their generality and practical importance
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summary of chapter 2
A range of methods are increasingly able to link the psychological study of memory with the brain systems that underpin it (see Table 2.1).
* Among the earliest approaches are those based on the study of patients with memory deficits resulting from brain damage.
* Rare single cases with a very specific deficit are particularly informative theoretically, but group studies are of considerable practical importance.
* Patient-based approaches are supplemented by a range of methods of observing the structure of the healthy brain.
* Approaches began with computerized tomography (CT) relying on X-rays.
* This was followed by magnetic resonance imaging (MRI) which relies on the fact that different structures within the brain differ in their response to the energy produced by a surrounding magnetic field.
* In an extension of MRI, diffusion tensor imaging (DTI) is able to image the white matter tracts that connect different areas of the brain.
* A range of methods allow us to observe the working brain in real time. They include:
* Stimulation by implanted electrodes, and transcranial magnetic stimulation (TMS). Both allow specific brain functions to be experimentally and temporarily disrupted.
* Electro-encephalography (EEG) reflects the ongoing electrical activity of the brain and its response to specific stimuli, through event-related potentials (ERPs).
* A more recent electrophysiological development is that of magneto-encephalography (MEG) which relies on the magnetic activity of the brain.
* A number of measures have developed for studying the activity of the brain through blood flow. These include:
* Positron emission tomography (PET) which depends on injecting and then detecting a radioactive tracer within the blood. The need for radio activity is a problem, resulting in the development of noninvasive research methods.
* Functional magnetic resonance imaging (fMRI) also depends on imaging blood flow in areas of the brain assumed to be activated by psychological processes, but is noninvasive, relying on picking up the tiny magnetic forces generated in the brain.
* Multi-voxel pattern analysis (MVPA) uses a powerful statistical technique to identify patterns of activity associated with specific cognitive activities.
* Studies at the cellular level although of crucial basic importance have so far not connected strongly with the psychology of memory.
* Genetic studies are also promising but not yet influential in the memory field
