Difficulty: Intermediate | Prerequisites: Chapter 4 (hippocampus, frontal lobes, amygdala).
This chapter covers how memories are formed, stored, and retrieved, and why we forget. It builds directly on the brain anatomy from Chapter 4, particularly the hippocampus, frontal lobes, and amygdala. Memory is not a single system but a set of interacting processes, and understanding them is essential for later topics on cognition (Ch. 8), emotions (Ch. 10), and mental disorders (Ch. 13). The case of patient HM, who lost the ability to form new long-term memories after hippocampus removal, is the thread running through the chapter.
Memory involves three stages: encoding (translating experience into neural codes), storage (retaining those codes), and retrieval (accessing them later). Short-term/working memory holds a small amount of information briefly; long-term memory is nearly limitless. Memories can be explicit (conscious recall) or implicit (unconscious, like motor skills). The hippocampus is critical for forming new declarative memories, the frontal lobes coordinate encoding and retrieval, and the amygdala strengthens emotionally charged memories. Forgetting happens mainly through interference, not decay.
Sensory memory
A brief trace left on the nervous system by lights, smells, and sounds, lasting a split second. Unless attention is directed to it, the information vanishes.
Iconic memory
Visual sensory memory; lasts about one-third of a second.
Echoic memory
Auditory sensory memory. Together with iconic memory, these allow us to perceive the world as continuous rather than as discrete bits.
Short-term memory (STM) / immediate memory
Holds a small amount of information (about 7 items, plus or minus 2) for roughly 20 seconds before it is displaced. Think of it as the brain's RAM.
Memory span
The number of items (roughly 7 plus or minus 2) that can be held in STM. Sometimes used as a proxy for IQ.
Chunking
Breaking material into meaningful units to make it easier to remember. The more familiar you are with a subject, the larger your chunks.
Working memory
An active processing system (replacing the older passive STM model) that keeps information available for problem-solving and other tasks. Has three components: the central executive, the phonological loop, and the visuospatial sketchpad.
Central executive
The "boss" of working memory. Encodes information from sensory systems and filters what is important enough to store in long-term memory.
Phonological loop
Encodes auditory information; involved in speaking or reading to yourself. People confuse consonants that sound alike rather than look alike, because words are processed by sound in working memory.
Visuospatial sketchpad
Handles spatial layouts and visual information. Patients with damage to the phonological loop can still have intact visuospatial memory.
Long-term memory (LTM)
Nearly limitless storage, similar to a hard drive.
Primacy effect
Better memory for items presented first in a list.
Recency effect
Better memory for items presented most recently.
Serial position effect
The combined tendency to recall the beginning and end of a list better than the middle.
Explicit memory / declarative memory
Conscious processes used to remember specific information that can be "declared" or brought to mind.
Episodic memory
Memories of personal past experiences (a subcategory of explicit memory).
Semantic memory
Knowledge of facts, concepts, and general information (a subcategory of explicit memory). "Three strikes and you're out."
Implicit memory
Remembering without deliberate effort or awareness. Brushing your teeth, remembering how to get to class.
Procedural memory / motor memory
Involves motor skills, habits, and behaviours. Unconscious and automatic.
Repetition priming
Improved identification or processing of a stimulus that has been previously experienced.
Encoding
Translating perceptual experiences into representations or codes for storage.
Levels of processing
The deeper an item is encoded (semantic processing is deepest), the more meaning it has and the better it is remembered. Semantic > acoustic > visual.
Maintenance rehearsal
Simply repeating an item over and over.
Elaborative rehearsal
Encoding information in meaningful ways; produces stronger memory than maintenance rehearsal.
Schemas
Cognitive structures that help us perceive, organise, process, and use information based on past experience. People fill in holes and overlook inconsistencies.
Spreading activation
In a network of associations, activating one node increases the likelihood that closely associated nodes will also be activated.
Retrieval cues
Anything that helps access information from LTM. Explains why recognition is easier than recall.
Context-dependent memory
Enhanced recall when in the same setting as original learning.
Encoding specificity principle
Any stimulus encoded with an experience can later trigger the memory of that experience.
State-dependent memory
Better recall when in the same physiological state (drunk, sober, high) as during encoding. Best recall is always sober.
Consolidation
Transfer of immediate memory to long-term memory.
Reconsolidation
The theory that once memories are reactivated, they must be re-stored, and can change in the process.
Memory modulators
Neurotransmitters that can weaken or enhance memory storage (e.g. epinephrine, norepinephrine).
Anterograde amnesia
Inability to store new explicit memories (as seen in patient HM).
Retrograde amnesia
Loss of past memories for events, facts, people, or personal information.
Korsakoff's syndrome
A severe memory disturbance linked to chronic alcoholism.
Flashbulb memories
Vivid memories of the circumstances surrounding a shocking or emotionally charged event. More accurate than random memories but still sometimes inaccurate.
Proactive interference
Old information inhibits the ability to learn new information (old locker combo blocking the new one).
Retroactive interference
New information inhibits the ability to recall old information (new combo blocking the old one).
Hemispheric Encoding Retrieval Asymmetry (HERA)
The left frontal lobe is more active during encoding of verbal stimuli; the right frontal lobe is more active during episodic retrieval.
Von Restorff effect
Distinctive events are better remembered than trivial ones.
Cryptomnesia
When a person believes they have come up with a new idea, but they have actually retrieved an old one from memory without attributing it to its source.
Source amnesia
Memory for an event without remembering where or how the information was encountered.
Confabulation
False stories produced by a person who genuinely believes them, often to fill gaps in memory.
Patient HM had his hippocampus removed to treat epilepsy
He could no longer form new long-term memories (anterograde amnesia)
He could still remember mechanical motor skills (procedural memory intact)
Demonstrates that the hippocampus is critical for forming new declarative memories but not for procedural memory
Atkinson's modal memory model: sensory memory, short-term memory, long-term memory (standard but inaccurate and incomplete)
Sensory memory: brief trace; iconic (visual, ~1/3 second) and echoic (auditory); together they create fluid perception
STM: ~7 items (plus or minus 2), ~20 seconds; displaced by new information; chunking increases capacity
Working memory replaced the passive STM model: central executive (boss), phonological loop (auditory/verbal), visuospatial sketchpad (spatial/visual)
LTM: nearly limitless; primacy effect (first items remembered better), recency effect (last items remembered better); serial position effect combines both
Encoding: translating experiences into codes; deeper processing = better memory; levels of processing: semantic (deepest) > acoustic > visual
Maintenance rehearsal (rote repetition) vs. elaborative rehearsal (encoding meaningfully); elaborative is far superior
Distributed practice is better than massed/crammed practice; overlearning helps recall
We remember what helps us adapt to the environment or is personally meaningful
Schemas: cognitive structures that shape incoming information; people fill in gaps and interpret based on past experience; can cause distortions (repeating a Native American story filtered through one's own culture)
Spreading activation: activating one node in a network of associations activates related nodes
Retrieval cues: anything that helps access LTM; recognition is easier than recall because cues are provided
Context-dependent memory: enhanced recall in the same physical setting
State-dependent memory: enhanced recall in the same physiological state (but best recall is always sober)
Encoding specificity principle: any stimulus encoded with an experience can later trigger the memory
Explicit/declarative memory: conscious recall; subdivided into episodic (personal experiences) and semantic (facts/knowledge)
Implicit memory: unconscious; includes procedural memory (motor skills, habits) and repetition priming
The false fame effect: names encountered the day before are later mistakenly judged as famous
Advertisers exploit implicit memory to associate celebrities with brands
Hippocampus and rhinal cortex: most important for declarative memory; Mishkin's animal model demonstrated this; hippocampus also critical for spatial memory (Morris maze test, place cells)
Frontal lobes: important for episodic memory, working memory, time sequences, encoding and retrieval; deeper encoding activates the frontal lobe more; frontal lobe injury impairs time-sequence memory
HERA: left frontal lobe encodes verbal stimuli; right frontal lobe retrieves episodic memories; nonverbal material activates the right side
Amygdala: controls modulating effects of neurotransmitters on memory; emotional events are "burned in"; arousing events cause greater norepinephrine activity, strengthening memory; emotional memory activates the right amygdala in men, the left in women
Memory modulators: epinephrine releases glucose, influencing memory storage; norepinephrine in the amygdala enhances memory; NMDA affects long-term learning (helped people overcome phobias); beta blockers reduced emotional memories after trauma
Consolidation: transfer from working memory to LTM; reconsolidation theory: reactivated memories must be re-stored and can change
Forgetting is necessary (minds would become cluttered); occurs rapidly at first, then levels off
Most forgetting is caused by interference, not decay
Proactive interference: old info blocks new learning
Retroactive interference: new info blocks recall of old info
Blocking: temporary inability to recall (tip-of-the-tongue phenomenon)
The seven sins of memory:
Transience: reduced memory over time
Absentmindedness: failure to pay attention (losing keys)
Blocking: inability to retrieve needed info (someone's name)
Misattribution: assigning a memory to the wrong source (misquoting)
Suggestibility: altering memory because of misleading info ("smashed" vs. "hit" in car crash studies)
Bias: current knowledge distorting memory of past events
Persistence: unwanted memories resurfacing (PTSD)
Retrograde amnesia: loss of past memories
Anterograde amnesia: inability to form new memories (HM, Korsakoff's syndrome)
Flashbulb memories: vivid memories of shocking events; more accurate than random memories due to stress hormones, but not perfect
Von Restorff effect: distinctive events remembered better
Eyewitness testimony: often unreliable; juries are heavily influenced by it; eyewitnesses are equally confident whether right or wrong; the fusiform face area shows more activity for in-group faces
Suggestibility: word choice in questions alters memories ("smashed" vs. "hit"); false memories can be implanted
Source amnesia: remembering an event but not where you learned it
Childhood amnesia: inability to remember events before age three (likely due to immature frontal lobes or lack of linguistic development)
Confabulation: false stories created to fill memory gaps
Change blindness: failing to notice a person has been swapped during a brief interruption
Repressed memories: controversial; may be influenced by therapists; police can induce false confessions, especially under high stress
Distributed practice (spaced repetition) is the evidence-based way to study for exams. Elaborative rehearsal, putting material in your own words, is why study groups and teaching others works. Understanding suggestibility in eyewitness testimony has led to reforms in police interview procedures and lineup construction.
Students think forgetting is caused by memories "decaying." Most forgetting is caused by interference from other information.
Students confuse retrograde and anterograde amnesia. Retrograde = loss of old memories. Anterograde = inability to form new ones.
Students believe flashbulb memories are perfectly accurate. They are more accurate than ordinary memories, but still prone to error.
Students assume all memory is conscious. Implicit memory (procedural skills, priming) operates without awareness.
⚠️ Know the three components of working memory (central executive, phonological loop, visuospatial sketchpad).
⚠️ The distinction between episodic and semantic memory (Tulving) is frequently tested.
⚠️ HM's case: what it demonstrates about the hippocampus, anterograde amnesia, and the dissociation between declarative and procedural memory.
⚠️ The seven sins of memory: be able to name, define, and give an example of each.
⚠️ Proactive vs. retroactive interference: know which direction the interference runs.
⚠️ HERA: left frontal = encoding verbal; right frontal = episodic retrieval.
Fill in the blank: The capacity of short-term memory is roughly __________ items. (7, plus or minus 2)
True or False: Elaborative rehearsal is less effective than maintenance rehearsal. (False. Elaborative is more effective.)
Fill in the blank: The inability to form new long-term memories is called __________ amnesia. (Anterograde)
True or False: The hippocampus is important for procedural memory. (False. It is important for declarative memory. Procedural memory is intact even with hippocampal damage, as shown by HM.)
Fill in the blank: When old information interferes with learning new information, it is called __________ interference. (Proactive)
Q: Explain the difference between explicit and implicit memory, and give an example of each.
A: Explicit (declarative) memory involves conscious recall of information and can be subdivided into episodic (personal experiences) and semantic (facts). An example is remembering your last birthday party. Implicit memory operates without deliberate effort; procedural memory (knowing how to ride a bike) and repetition priming (faster recognition of previously seen words) are both examples.
Q: Describe the serial position effect and explain how it relates to the distinction between STM and LTM.
A: The serial position effect is the tendency to recall items at the beginning (primacy effect) and end (recency effect) of a list better than items in the middle. The primacy effect is thought to occur because early items receive more rehearsal and are transferred to LTM. The recency effect is thought to occur because the last items are still in STM when recall is tested.
Q: What are the seven sins of memory? Name each and provide a brief example.
A: Transience (forgetting a plot over time), absentmindedness (losing keys due to inattention), blocking (failing to recall someone's name), misattribution (misquoting a source), suggestibility (developing false memories from leading questions), bias (recalling past attitudes as similar to current ones), and persistence (unwanted traumatic memories recurring, as in PTSD).
Q: How does the amygdala influence memory, and what role do memory modulators play?
A: The amygdala modulates the strength of emotional memories. Arousing events cause greater norepinephrine activity, which strengthens memory storage. Epinephrine releases glucose that enters the brain and influences storage. This is why emotional events are remembered more vividly. Beta blockers can reduce the formation of emotional memories after trauma, and NMDA has been shown to help people overcome phobias by enhancing long-term learning.
This chapter builds on the brain anatomy in Chapter 4 (hippocampus, frontal lobes, amygdala). Memory processes connect to learning mechanisms in Chapter 6 (classical conditioning, reinforcement). The role of emotion in memory connects directly to Chapter 10 (emotions and health, PTSD, stress). Schemas and cognitive distortions connect forward to Chapter 8 (cognition, reasoning biases) and Chapter 13 (cognitive models of depression).
memory, sensory memory, iconic memory, echoic memory, short-term memory, STM, working memory, central executive, phonological loop, visuospatial sketchpad, long-term memory, LTM, primacy effect, recency effect, serial position effect, chunking, memory span, explicit memory, declarative memory, episodic memory, semantic memory, implicit memory, procedural memory, motor memory, repetition priming, encoding, storage, retrieval, levels of processing, maintenance rehearsal, elaborative rehearsal, schemas, spreading activation, retrieval cues, context-dependent memory, state-dependent memory, encoding specificity principle, consolidation, reconsolidation, memory modulators, epinephrine, norepinephrine, amygdala, hippocampus, frontal lobes, HERA, anterograde amnesia, retrograde amnesia, Korsakoff's syndrome, HM, flashbulb memories, seven sins of memory, transience, absentmindedness, blocking, misattribution, suggestibility, bias, persistence, proactive interference, retroactive interference, Von Restorff effect, cryptomnesia, source amnesia, confabulation, change blindness, eyewitness testimony, false memories, childhood amnesia, tip of the tongue, PSY 320, health psychology