Understanding Human Memory Encoding & Storage

1. Cognitive ProcessesPSY 334 Chapter 6 – Human Memory: Encoding and Storage

2. 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.

3. 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.

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

5. Retention Times Long-term memory retrieval Short-term (working) memory Sensory store Environment encoding 1-3 seconds 15-25 seconds 1 sec to a lifetime

6. 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.

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

8. Sperling’s Results Delay

9. 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.

10. 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)

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

12. 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.

13. 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.

14. 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.

15. Word-Lenth Determines Forgetting

16. 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.

17. Delayed Matching to Sample

18. 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.

19. 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.

20. 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.

21. The ACT Model

22. 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)

23. 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.

24. 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.

25. Meyer and Schvaneveldt

26. 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.

27. 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.

28. Learning Curves

29. Practicing Addition Problems

30. 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.

31. Neural Changes Mirror Behavioral Changes

32. 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.

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

34. 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.

35. 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.

36. 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.

37. 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).

38. 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.

39. Slamecka & Graf’s Results

40. 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).

41. “This Old Man” Song • http://www.youtube.com/watch?v=3cYf9vkW_xU • http://www.totlol.com/watch/5d-6Q5V79CM/This-Old-Man/0/

42. Pegword System 1 – bun 2 – shoe 3 – tree 4 – door 5 – hive 6 – sticks 7 – heaven 8 – gate 9 – wine 10 -- hen

43. 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.

44. Awareness of Learning

45. 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

46. 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.