Cognitive Processes PSY 334 Chapter 6 – Human Memory: Encoding and Storage

Ebbinghaus  First rigorous investigation of human memory –  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.

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.

The Three-Stage Model Environment Sensory store Short-term (working) memory Long-term memory Responses Executive control processes Sensation/perception Attention encoding retrieval

Retention Times Environment Sensory store Short-term (working) memory Long-term memory encoding retrieval 1-3 seconds15-25 seconds1 sec to a lifetime

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.

Sperling’s Partial Report A medium tone signals the subject to report the letters in this row

Sperling’s Results Delay

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.

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)

Shepard’s Results Number of intervening items Probability of recalling the target item

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 may go directly to LTM.

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.

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. Visuopatial sketchpad – rehearses images. Central executive – controls other systems.

Word-Lenth Determines Forgetting

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.

Delayed Matching to Sample

Importance of Frontal Cortex  In primates, working memory is localized to the frontal cortex.  Delayed matching to sample task: Monkeys are shown food that is then hidden. Later they are given a chance to locate it.  Monkeys with frontal lobe lesions cannot do this task.

Activation  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.

Anderson’s ACT Model  ACT – Adaptive Control of Thought  Moses Effect -- subjects shown the words Bible, animal and flood should recall Noah but recall Moses instead. 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.

The ACT Model

Factors Affecting Activation  How recently we have used the memory: Loftus – manipulated amount of delay 1.53 sec first time, then 1.21, 1.28, and 1.33 with 3 items intervening.  How much we have practiced the memory – how frequently it is used. Anderson’s study (sailor is in the park)

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.

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.

Meyer and Schvaneveldt

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.

Power Function  Each time we use a memory trace, it gradually becomes a little stronger.  Power law of learning: T = 1.40 P T is recognition time, P is days of practice. Linear when plotted on log-log scale.

Learning Curves

Practicing Addition Problems

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.

Neural Changes Mirror Behavioral Changes

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.

Activation in Prefrontal Cortex Words activate left prefrontal cortex Pictures activate right prefrontal cortex Hemodynamic = blow flow during brain activity

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.

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.

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.

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).

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.

Slamecka & Graf’s Results

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).

“This Old Man” Song  

Pegword System 1 – bun 2 – shoe 3 – tree 4 – door 5 – hive 6 – sticks 7 – heaven 8 – gate 9 – wine hen

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 work 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.

Awareness of Learning

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.  Thatcher’s resignation: 60% memory for UK subjects, 20% non- UK

Self-Reference Effect  Two explanations: People have special mechanisms for encoding info relevant to themselves. Info relevant to the self is rehearsed more often.  High arousal may enhance memory.  Memory is better for words related to the self – perhaps due to better elaboration.