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Cognitive Processes PSY 334 Chapter 6 – Human Memory: Encoding and Storage
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Ebbinghaus First rigorous investigation of human memory – 1885. Taught himself nonsense syllables DAX, BUP, LOC Savings – the amount of time needed to relearn a list after it has already been learned and forgotten. Forgetting function – most forgetting takes place right away.
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Memory Models Atkinson & Shiffrin – proposed a three- stage model including: Sensory store – if attended goes to STM Short-term memory (STM) – if rehearsed goes to LTM Long-term memory (LTM) No longer the current view of memory. Still presented in some books.
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The Three-Stage Model Environment Sensory store Short-term (working) memory Long-term memory Responses Executive control processes Sensation/perception Attention encoding retrieval
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Retention Times Environment Sensory store Short-term (working) memory Long-term memory encoding retrieval 1-3 seconds15-25 seconds1 sec to a lifetime
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Sensory Memory Holds info when it first comes in. Allows a person to extract meaning from an image or series of sounds. Sperling’s partial report procedure: A display of three rows of letters is presented. After it is taken away, a tone signals which row to report. Subjects were able to report most letters.
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Sperling’s Partial Report A medium tone signals the subject to report the letters in this row
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Sperling’s Results Delay
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Kinds of Sensory Stores Iconic memory – visual Bright postexposure field wipes out memory after 1 sec, dark after 5 sec. Echoic memory – auditory Lasts up to 10 sec (measured by ERP) Located in the sensory cortexes.
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Short Term Memory The original idea is that when info in sensory memory is paid attention to, it moves into short term memory. With rehearsal, it then moves into long term memory. STM has limited capacity, called memory span. Miller’s magic number (7 ± 2) New info pushes out older info (Shepard)
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Shepard & Teghtsoonian’s Results Number of intervening items Probability of recalling the target item
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Criticisms of STM Rate of forgetting seemed to be quicker than Ebbinghaus’s data, but is not really. Amount of rehearsal appeared to be related to transfer to long-term memory. Later it was found that the kind of rehearsal matters, not the amount. Passive rehearsal does little to achieve long-term memory. Information can go directly to LTM.
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Depth of Processing Craik & Lockhart – proposed that it is not how long material is rehearsed but the depth of processing that matters. Levels of processing demo.
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Working Memory Baddeley – in working memory speed of rehearsal determines memory span. Articulatory loop – stores whatever can be processed in a given amount of time. Word length effect: 4.5 one-syllable words remembered compared to 2.6 long ones. 1.5 to 2 seconds material can be kept. Visuospatial sketchpad – rehearses images Central executive – controls other systems.
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Word-Length Determines Forgetting
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Delayed Matching Task Delayed Matching to Sample – monkey must recall where food was placed. Monkeys with lesion to frontal cortex cannot remember food location. Human infants can’t do it until 1 year old. Regions of frontal cortex fire only during the delay – keeping location in mind. Different prefrontal regions are used to remember different kinds of information.
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Delayed Matching to Sample
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Activation and Long-Term Memory Activation – how available information is to memory: Probability of access – how likely you are to remember something. Rate of access – how fast something can be remembered. From moment to moment, items differ in their degree of activation in memory.
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Anderson’s ACT Model ACT – Adaptive Control of Thought Subjects shown the word “flood” should recall Noah but do not without “Bible,” “animal” and “flood” together. When given the word flood they think of Mississippi or Johnstown but not Noah. Why? Recall is based on both baseline and activation from associated concepts. Moses and Jesus have higher baselines.
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Moses Illusion How many animals of each species did Moses bring onto the ark? People respond 2 rather than none. This occurs because people do not focus attention on who did it, and because Moses and Noah are both Biblical characters. This is a semantic illusion.
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The ACT Model
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Spreading Activation Activation spreads along the paths of a propositional network. Related items are faster to recall. Associative priming – involuntary spread of activation to associated items in memory. Kaplan’s dissertation – cues to solving riddles hidden in the environment led to faster solutions.
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Associative Priming Meyer & Schvaneveldt – spreading activation affects how quickly words are read. Subjects judged whether pairs of related & unrelated items were words. Judgments about related words were faster.
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Meyer and Schvaneveldt
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Practice and Strength The amount of spreading activation depends on the strength of a memory. Memory strength increases with practice. Greater memory strength increases the likelihood of recall.
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Power Function Each time we use a memory trace, it gradually becomes a little stronger. Power law of learning: T = 1.40 P -0.24 T is recognition time, P is days of practice. Linear when plotted on log-log scale.
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Learning Curves
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Practicing Addition Problems
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Long Term Potentiation (LTP) Neural changes may occur with practice: Long-term potentiation (LTP) in hippocampus. Repeated electrical stimulation of neurons leads to increased sensitivity. LTP changes are a power function.
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Neural Changes Mirror Behavioral Changes
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Neural Correlates of Encoding Better memory occurs for items with stronger brain processing at the time of study: Words evoking higher ERP signals are better remembered later. Greater frontal activation with deeper processing of verbal information. Greater activation of hippocampus with better long-term memory.
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Activation in Prefrontal Cortex Words activate left prefrontal cortex Pictures activate right prefrontal cortex Hemodynamic = blow flow during brain activity
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Factors Influencing Memory Study alone does not improve memory – what matters is how studying is done. Shallow study results in little improvement. Semantic associates (tulip-flower) better remembered than rhymes (tower-flower), 81% vs 70%. Better retention occurs for more meaningful elaboration.
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Elaborative Processing Elaboration – embellishing an item with additional information. Anderson & Bower – subjects added details to simple sentences: 57% recall without elaboration 72% recall with made-up details added Self-generated elaborations are better than experimenter-generated ones.
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Self-Generated Elaborations Stein & Bransford – subjects were given 10 sentences. Four conditions: Just the sentences alone – 4.2 adjectives Subject generates an elaboration – 5.8 Experimenter-generated imprecise elaboration – 2.2 Experimenter-generated precise elaboration – 7.8 Precision of detail (constraint) matters, not who generates the elaboration.
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Advance Organizers PQ4R method – use questions to guide reading. 64% correct, compared to 57% (controls) 76% of relevant questions correct, 52% of non-relevant. These study techniques work because they encourage elaboration. Question making and question answering both improve memory for text (reviewing is better than seeing the questions first).
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Meaningful Elaboration Elaboration need not be meaningful – other sorts of elaboration also work. Kolers compared memory for right-side- up sentences with upside-down. Extra processing needed to read upside down may enhance memory. Slamecka & Graf – compared generation of synonyms and rhymes. Both improved memory, but synonyms did more.
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Slamecka & Graf’s Results
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Mnemonics Method of Loci – place items in a location, then take a mental walk. Peg-word System – use peg words as a structure and associate a list of items with them using visualization. Create acronyms for lists of items. Convert nonsense syllables (DAX, GIB) into meaningful items by associating them with real words (e.g., DAD).
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“This Old Man” Song http://www.youtube.com/watch?v=3cYf9vkW_xU http://www.youtube.com/watch?v=3cYf9vkW_xU http://www.totlol.com/watch/5d-6Q5V79CM/This-Old-Man/0/ http://www.totlol.com/watch/5d-6Q5V79CM/This-Old-Man/0/
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Pegword System 1 – bun 2 – shoe 3 – tree 4 – door 5 – hive 6 – sticks 7 – heaven 8 – gate 9 – wine 10 -- hen
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Incidental Learning It does not matter whether people intend to learn something or not. What matters is how material is processed. Orienting tasks: Count whether word has e or g. Rate the pleasantness of words. Half of subjects told they would be asked to remember words later, half not told. No advantage to knowing ahead of time.
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Awareness of Learning
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Flashbulb Memories Self-reference effect -- people have better memory for events that are important to them and close friends. Flashbulb memories – recall of traumatic events long after the fact. Seem vivid but can be very inaccurate, just like everyday memories. Thatcher’s resignation: 60% memory for UK subjects, 20% non- UK
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9/11 Memories Talairco & Rubin (2003) found that 9/11 story-consistent details decreased and inconsistent details increased with time. Rate and amount of both kinds of details were closely similar for flashbulb & everyday memories. Sharot et al. (2007) reported greater activity in the amygdala for people closer to ground zero, when recalling 3 yrs later
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Arousal & the Self-Reference Effect Two explanations: Activation of the amygdala involves a biological mechanism reinforcing memory for events important to us. Info relevant and important to the self is rehearsed more often – resulting in better elaboration. High arousal may enhance memory above and beyond rehearsal.
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