9/18 Notes Memory: Encoding, Storage, and Retrieval — Comprehensive Notes

Memory is multiple processes and multiple storage types

• Memory is not a single process (not just a filing cabinet). It involves multiple processes: encoding, storage, retrieval, and multiple storage types.
• Encoding: the process of paying attention, thinking about, rehearsing, or practicing information to enter memory. In last class we covered what gets encoded (organization, imagery) and factors affecting encoding (e.g., serial position effect). Rehearsal is part of encoding.
• Retrieval depends on how information is encoded and stored; organization and connections made during encoding affect how easily we can retrieve later.

Core processes in memory

• Three memory processes: encoding, storage, retrieval (not strictly linear, but they are functionally distinct).
• Today’s focus: storage (where memory is kept) and retrieval (how we get it back).
• Retrieval requires cues or prompts to access stored information; without effective retrieval cues, information can be effectively forgotten even if stored.

Three types of memory storage (within storage)

• There are three storage types distinguished by capacity and duration:
  • Sensory memory (short-lived, high capacity but extremely brief)
  • Short-term/Working memory (limited capacity, brief duration, active thinking)
  • Long-term memory (potentially unlimited capacity and duration)
• These three storage types are not causally linked boxes in a simple sequence; they’re distinct storage systems that information passes through on its way to long-term memory.

Sensory memory

• Definition: sensory memory holds all currently experienced sensory information for a fraction of a second; exists for each sense (visual, auditory, tactile, etc.).
• Duration and capacity:
  • Visual sensory memory (iconic): lasts about $50 \,\text{ms}$ (a fraction of a second).
  • Auditory sensory memory (echoic): lasts about $3\text{--}4\,\text{s}$.
  • Tactile sensory memory (haptic): lasts about $1\text{ s}$ (roughly one second).
• Function: captures everything you see/hear/feel at the moment; you decide what to pay attention to and rehearse to move it into short-term/working memory.
• Classic capacity finding (Spurling, 1960):
  • When shown a 3x3 grid of letters for about $50\,\text{ms}$, free recall yields about four letters (≈ 44%).
  • With a cue (tone) indicating which row to recall, recall rises to 100% for that row (example: top, middle, bottom).
  • This suggests sensory memory has large capacity, but information decays almost instantly unless attended to and transferred to short-term memory.
• Visual vs auditory cues and partial reporting illustrate that sensory memory can hold a large amount briefly, but decay is rapid without attention.
• Practical implication: you have a very brief window to decide what to attend to in the environment; attention is critical for preserving information into working memory.

Short-term memory (Working memory)

• Definition: the memory you are actively using right now; the information you are thinking about at the moment.
• Capacity: $7 \pm 2$ items (often cited as 5–9 items) making up a working set.
• Duration: about $20\text{ seconds}$ without rehearsal; unless you rehearse, it fades quickly.
• Chunking increases effective capacity: organizing items into meaningful chunks (e.g., digits, letters, acronyms, phrases) increases the number of items you can manage by grouping multiple elements into a single chunk.
• Examples:
  • Unrelated letters: you can hold about 5–9 letters.
  • Group into acronyms/words to hold more information as fewer chunks (e.g., abbreviation-based chunks).
• How information enters short-term memory: from sensory memory when attention is paid; rehearsal helps keep it active and facilitates transfer to long-term memory.
• Serial recall and interference: short-term memory can be disrupted by processing tasks (e.g., counting backwards) to prevent rehearsal of a string of items; recall declines as interference increases.
• Experimental illustration:
  • Present three consonants, e.g., $\text{X} \text{S} \text{T}$.
  • Immediately perform a distracting task (e.g., count backwards from 100 by threes) for a delay, then recall the consonants.
  • Data show recall drops rapidly with delay, illustrating the limited duration of short-term memory if not reinforced.
• Retrieval from short-term memory is used to respond (e.g., answer quiz questions, decide what to say in a conversation).

How information moves to long-term memory

• If information is encoded well and repeatedly rehearsed, it moves into long-term memory for later retrieval.
• Retrieval from long-term memory brings information back to short-term memory for use and response, after which it can be stored again in long-term memory.
• The long-term store can hold vast amounts of information for potentially a lifetime (barring disease or cognitive decline).

Long-term memory

• Capacity: effectively unlimited; information can be stored for a lifetime with proper encoding.
• Forgetting is possible; information can decay or become less accessible over time.
• Forgetting curve (Ebbinghaus):
  • Immediate recall is 100% (immediately after learning).
  • With time, recall drops quickly: after about $20\ \text{minutes}$, about a third of material is forgotten (≈ 66% retained).
  • After about an hour, around half is forgotten (≈ 50% retained).
  • After days to weeks, retention falls to around 20% (≈ 80% forgotten).
  • The forgetting curve is steep initially and flattens over time.
• Relearning and retention: relearning material after forgetting leads to faster reacquisition and better long-term retention; the more you relearn, the more you retain over time (spaced/repeated encoding).
  • Retention after successive relearning shows that after each relearning, the amount forgotten between relearnings decreases and final retention stabilizes around 90–95% with repeated practice.
• Implications for study: spacing and repeated retrieval are beneficial; restudy and spaced practice improve long-term retention.

Forgetting curves and strategies to combat forgetting

• Repetition and spacing counteract rapid initial forgetting by strengthening encoding and retrieval pathways.
• Interference is a major cause of forgetting in long-term memory; it can be proactive (old information interferes with new learning) or retroactive (new information interferes with old learning).
• Proactive interference example: learning French first makes it harder to learn Spanish later because French words intrude on recall of Spanish.
• Retroactive interference example: learning a new PIN or password can make it harder to recall the old one.
• Sleep vs wakefulness and interference (experimental finding): a nap can reduce interference; participants who slept between learning and recall retained more information than those who stayed awake and encountered more new information.

Retrieval and priming

• Retrieval starts with cues: cues help locate the target information in memory.
• Priming: exposure to one stimulus unconsciously facilitates recall of related information; it can trigger a web of related concepts connected in long-term memory.
• How priming works:
  • Example: hearing a cue word like “rabbit” can trigger related associations (white, fuzzy, springtime, petting zoo, etc.).
  • A rich network of associations makes it easier to retrieve related items when prompted by a cue.
• The role of encoding quality in retrieval: organization, imagery, and meaningful encoding create more robust associative networks, making retrieval easier.
• Applications to tests:
  • Priming in exam questions can guide recall; recognizing which primes (keywords) are present helps determine what can be retrieved.
  • Mnemonic techniques (imagery, acronyms, method of loci) aid retrieval by creating strong, organized memory hooks.
• Location and mood context effects (context-dependent memory):
  • Context similarity between learning and recall enhances retrieval (e.g., scuba divers learning words underwater vs on land showed context-dependent recall advantages).
  • Mood-congruent memory: recall is better when mood matches between encoding and retrieval; being in a similar mood can aid access to memories.
  • External context (location) and internal context (mood) influence how well information is retrieved; returning to a learning environment can trigger memory recall due to contextual cues.
• Location effects on memory recall: being in the same room can improve recall of what was learned there; changing rooms can impair recall due to loss of context cues.
• Mood and depression: negative mood or depression can bias recall toward memories that match the mood, potentially creating a vicious cycle; therapy can address this by redirecting thought patterns.

The brain and memory: where memory lives and how it’s supported

• Lashley (1950) classic thought: memories must be stored in a specific brain region; he trained rats to navigate a maze and then lesioned different brain areas to identify a memory store. He found no single brain region essential for maze memory, suggesting memory is distributed rather than localized.
• Contemporary view acknowledges distributed memory processes and multiple brain systems.
• Distinct memory systems and brain areas:
  • Cerebellum: involved in procedural or how-to memories (e.g., riding a bicycle, dancing, riding a bike); stores motor memory and skill-based learning.
  • Hippocampus: involved in the formation and processing of explicit memories (facts and events); not the final storage site for all explicit memories but crucial for binding and consolidating them; damage can disrupt formation of new explicit memories while leaving some procedural memory intact (as in patient studies with hippocampal lesions).
  • Hormones: arousing hormones can enhance memory formation, particularly in emotionally charged situations; stress or emotionally salient experiences can lead to stronger memories.
• A classic demonstration (hippocampus): a patient who had hippocampus removed could not recall having learned a task (e.g., the Tower of Hanoi-like puzzle) but could still perform the task, showing dissociation between explicit recall and procedural memory.
• The current understanding: memory involves networks across brain regions; encoding, consolidation, and retrieval recruit different circuits depending on the type of memory.

Practical implications for studying and memory optimization

• Emphasize deep encoding with imagery, organization, and meaningful connections to improve retrieval likelihood.
• Use retrieval-practice and spaced repetition to combat forgetting and strengthen long-term retention.
• Create strong retrieval cues during studying (primes, contextual cues, and consistent study contexts) to improve recall.
• Be mindful of mood and context; studying and testing in similar contexts and moods can facilitate retrieval (context/mood congruence effects).
• Use mnemonics and visual imagery to create dense associative networks.
• Consider sleep and rest as part of learning strategy; sleep helps consolidate memories and can reduce interference.
• When studying for exams, consider actively identifying primes in questions and explicitly linking them to encoded material to guide retrieval.

Summary of key numerical and conceptual references

• Memory storage types and capacities:
  • Sensory memory capacity: effectively all that is sensed for a moment, but duration is $ext{fraction of a second}$; specific experiments show iconic memory lasts around $50\,\text{ms}$ and echoic memory lasts $3\text{--}4\,\text{s}$.
  • Short-term/working memory capacity: $7 \pm 2$ items (often summarized as 5–9) and duration about $20\,\text{seconds}$ without rehearsal.
  • Long-term memory capacity: effectively unlimited, duration may be a lifetime, with some information decaying over time without rehearsal.
• Spurling (1960): iconic memory capacity about four letters; with cueing, row recall reaches $100\%$; with delays, recall drops rapidly, showing sensory memory decoding depends on attention and timing.
• Ebbinghaus forgetting curve: immediate recall 100%; after $20\ ext{minutes}$, about a third forgotten; after an hour, ~50% forgotten; after days to weeks, ~80% forgotten; relearning improves retention with each repetition, approaching about 90–95% after multiple relearnings.
• Proactive vs retroactive interference: old learning interferes with new (proactive) and new learning interferes with old (retroactive).
• Context and mood effects: context-dependent memory (location-based recall) and mood-congruent memory (recall better in the same mood as encoding).
• Sleep and interference: napping after learning reduces interference and improves retention compared to staying awake.

Key terms to study for exams

• Encoding, Storage, Retrieval
• Sensory memory (iconic, echoic, haptic)
• Short-term/Working memory
• Long-term memory
• Chunking
• Forgetting curve (Ebbinghaus) and relearning/retention curve
• Proactive and retroactive interference
• Priming and cues
• Context-dependent and mood-congruent memory
• Procedural vs explicit memory (cerebellum vs hippocampus)
• Neurotransmitter changes during learning; distributed memory networks
• Mnemonics and imagery techniques
• Sleep’s role in memory consolidation