Memory
Definition: retention of information over time
Different abilities: reflects different abilities, memory is not one thing
Memory reconstruction, not reproduction: memory is actively reconstructed, not passively reproduced
Three system:
- sensory memory
- short-term memory
- long-term memory
Memory system overview
Sensory memory
- holds sensory information
- each sense has its own system
- iconic (vision, 1/2 a second)
- echoic (hearing, 2-4 seconds)
- large capacity
- allows more elaborate perceptual processing
- duration is short, capacity is large
Short-term memory
Definition: hold information temporarily in your mind for analysis, also known as working memory
Span: limited to 5-9 items
Duration: 20-30 seconds without rehearsal
Decay:
Long-term memory
Definition: information acquired across lifespan
Explicit (declarative) definition: consciously recalled
Episodic: events in our lives
Semantic: facts of the world (knowledge and concepts)
Implicit (non-declarative) definition: does not require conscious thought
Procedural: habits and how to do things (skills and actions)
Priming: exposure to stimulus influences future response
Primacy: remembering things at the start of a list well
Recency: remembering things at the end of a list well
Three memory processes
Encoding: process of getting information into our memory
Storage: maintaining information over time
Retrieval: accessing information when you need it
Encoding
Importance of attention: unless you pay attention, it won’t be encoded
Mnemonics: learning aids or strategies that enhance later recall (e.g. PEMDAS)
Storage
Engrams: physical basis of memory, structural + functional changes in our CNS as a result of experience
Consolidation: stabilizes memory traces in CNS
Schemas
Definition: mental models or knowledge structures, gained through experience
Purpose in future situations:
Retrieval
- reactivation or reconstruction of memories from storage
Recall: generating remembered information on your own
Recognition: selecting previously remembered information from several options
Retrieval cue: hints that make it easier for us to recall information
Encoding and Retrieval
Encoding specificity:
Context-dependent memory: best when physical or external context between encoding and retrieval are similar
State-dependent memory: match in internal/mental context between encoding and retrieval
Mood-dependent memory: match in mood between encoding and retrieval
Karl Lashley
Study lesioning rat brains: tried to find where engrams are stored, trained rates to run mazes to create lesions in the brain
What it says about memory: no one area when lesioned created memory problems, engrams are not stored in a single place, are distributed in the brain
Donald Hebb
LTP: long term potential; strengthening connections between two neuron’s after they are both activated
LTD: long-term depression; weakening of connections between two neutrons after low or no activation between them
How LTP and LTD affect the synapse: neurone that fire together lead to an increase in vesicles containing neurotransmitter, and more receptors on the post-synaptic dendrite
Hippocampus:
Where and what it is:
Its role in memory: hippocampus as “memory index” in temporal lobe, memories stored across brain
Synaptic theory of memory
What it is and how it works: memories as relative weights (connection strength) between neurons
Brain regions and types of memory
Hippocampus: codes explicit memories, forming new memories
Cerebellum: related to implicit memories
Prefrontal cortex: semantic memory, working/short-term memory
H.M. and Amnesia
Story of H.M.: bilateral temporal lobe removal due to seizures, Brenda Milner (student of Hebb) discovered H.M. and anterograde amnesia
Amnesia: loss or disorder of memory
Anterograde amnesia: can’t form new memories
Retrograde amnesia: can’t access old memories
H.M.’s learning task:
H.M. went to a lobotomist looking to cure his severe seizures. The lobotomist removed most of his medial temporal lobe, including the hippocampus, amygdala, and entorhinal cortex. This cured his seizures but left him with anterograde amnesia (can’t form new memories). Scientists studied him, soon discovering that the medial temporal lobe played a large part memory creation, but they get stored in other places. His other attributes were left unaffected by the surgery.
Elizabeth Loftus
Misinformation effect:
Stop/yield sign example: If it was suggested in the question that there was a yield sign, the person answering was more likely to mention there being a yield sign even if there was a stop sign.
Car collision and verb choice example: When asking about the speed the car was going at, if the word “smashed” was used over a word like “hit” or “bumped,” the person answering was more likely to report faster speeds and include details that were not there like smashed glass.
Lost in the mall example: Loftus was able to implant memories that didn’t happen, like getting lost in a mall, and 6 out of 24 thought the memory was real.
Factors that affect eyewitness testimony
Confidence: testimonies are better at the time of the alleged crime, and get worse as time goes on
Race: testimonies are worse when the person is of a different race
Fixation on weapons: witnesses tend to fixate on weapons, not the person appearance
Flashbulb Memories: vivid and detailed emotional memories
Neisser & Harsch 1992 study: showed that 75% of memories 2 years later didn’t match original memory.