1. Short-Term Memory & Working Memory
Psychology 355: Cognitive Psychology Instructor: John Miyamoto 04/18/2018: Lecture 04-3
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2. Lecture probably ends here
Outline
Finish sensory memory topic.
How much information can be retained in Short-Term Memory (STM)?
How long does information last in STM?
Brown-Peterson task
Retroactive and proactive interference
Proactive interference and the Brown-Peterson paradigm
Lecture probably ends here
Psych 355,, Miyamoto, Spr '18
Finish Discussion of Duration of Information in Sensory Memory

3. Summary of Results for Duration of Sensory Memory
Amount of information in sensory memory decreases over time.
By a little more than 1.0 seconds it is gone.
(How do we know that the capacity of sensory memory is very large? With 0 delay, you can cue any position in the array and get accurate memory of what is at that position.)
Psych 355,, Miyamoto, Spr '18
Diagram of Standard Model: Conclusion re Capacity of Sensory Memory

4. Conclusion of Partial Report Experiment
Very large, possibly unlimited capacity.
Information decays to 0 in about 1 second.
Control Processes
Input
Sensory Memory
Short-Term Memory
Long-Term Memory
Output: Speech/Actions
UW Psych 355, Miyamoto, Spr '18
What Is Meant By Capacity Limits on Memory?

5. What Is Meant by Limits on Memory Capacity?
Limit on memory capacity refers to a limit on the amount of information that can be held in memory.
Not the amount of information that can be input to memory (encoding), and not the amount of information that can be retrieved from memory (retrieval).
Sensory memory – very large, approximately unlimited Short-Term memory – ? Long-Term memory – very large, approximately unlimited
Next: Introduction to Short-Term Memory & Working Memory
UW Psych 355, Miyamoto, Spr '18
Overview of Short-Term Memory & Working Memory

6. Overview of Short-Term Memory (STM) & Working Memory (WM)
Intermediate processing stage between sensory memory & long-term memory
Emphasis on quantitative aspects:
Limited in amount of information storage.
Limited duration of storage.
Working Memory (WM) – evolved out of the concept of STM
Same as above plus some additional ideas
Multicomponent system – verbal, visual-spatial, episodic components
Emphasis on manipulation of information & control of information flow.
UW Psych 355, Miyamoto, Spr '18
Three Important Aspects of STM

7. Three Important Characteristics of STM
Short-Term Memory = STM
STM has limited capacity
Active maintenance is needed to retain information in STM.
Without active maintenance information is quickly lost from STM.
Information in STM is high accessible.
Psych 355, Miyamoto, Spr '18
Capacity Limits on STM - Magical Number Seven Plus or Minus Two

8. What Are the Limits on STM Capacity?
George Miller, "The Magic Number Seven, Plus or Minus Two." What is this about?
Two Aspects of STM Capacity: Quantity & Duration
Quantity: How many separate pieces of information can be held in STM?
Duration: How long does information last in STM if we don't actively process it?
Psych 355, Miyamoto, Spr '18
Demo re Measurement of Memory Span

9. Demo: Memory Span for Digits
On each trial, you will see a sequence of numbers (digits) presented one after the other.
Your Task: Write down all of the digits in the order in which they were presented.
For example, if you see    Write down:
Psych 355, Miyamoto, Spr '18
Demo with 4 Digits – Fixation Point

10. Digit Span Trial with 4 Digits*
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Display Digits – Automatic Timer, 1 Sec. per Slide

11. Digit 7
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12. Digit 3
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13. Digit 2
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14. Digit 5
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15. What Were the Digits? Correct Answer 7 3 2 5
Demo with 10 Digits – Fixation Point
Psych 355, Miyamoto, Spr '18

16. Digit Span Trial with 10 Digits*
Display Digits – Automatic Timer, 1 Second per Slide
Psych 355, Miyamoto, Spr '18

17. Digit 9
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18. Digit 6
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19. Digit 2
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20. Digit 1
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21. Digit 6
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22. Digit 8
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23. Digit 1
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24. Digit 2
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25. Digit 5
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26. Digit 7
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27. What Were the Digits?
Correct Answer
Obviously, 10 digits are much harder to retain than 4 digits digits would be impossible to retain
Except possibly if you had special training to do this task.
Psych 355, Miyamoto, Spr '18
Memory Span for Digits: About 7  2

28. Memory Span for Digits: About 7  2
Clearly retaining 3 or 4 digits is easy. Retaining 15 or more digits is impossible.
Typical limit is around 7  2 is the memory span for digits
Psych 355, Miyamoto, Spr '18
Luck & Vogel (1997): Memory Span for Colors & Positions

29. Memory Span for Color & Location
Luck & Vogel (1997) is described in Figure 5.8 and Figure 5.9.
Subject’s Task:
Subject sees some colored squares on one slide followed by another slide with colored squares.
Subject’s task is to say whether the two slides are identical or different.
Result: Performance drops off radically after presentation contains more than 3 squares.
Psych 355, Miyamoto, Spr '18
Typical Results for Memory Span with Different Contents

30. Typical Results for Memory Span with Different Contents
We can repeat this experiment with different types of items.
Auditory digits
Nonsense syllables – E.g., "KOR", "PAV", "FUP", .....
Short words chosen at random – "BAT", "TOW", "EAT", .....
Long words chosen at random – "PERISCOPE", "BILATERAL", ....
George Miller's "Magic Number Seven Plus or Minus Two".
Measured memory span is somewhat different for different types of items.
More complex items  smaller memory span
But memory span is always limited, possibly
Conclusion: There is a strong capacity limit on STM, i.e., there is a limit on the total number of items that can be retained in STM.
Psych 355, Miyamoto, Spr '18
Return to "Magical Number 7 +/- 2: Raise Issue of Chunking

31. Magical Number Seven Plus or Minus Two
Miller, G. A. (1956) The magical number seven, plus or minus two: Some limits on our capacity for processing information. Psychological Review, 63, 81–97.
There is a strong limit on the quantity of information stored in STM.
Roughly the same limit applies to many different contents, e.g., digits, nonsense syllables, short words, long words, colors in different positions on a screen, tones of different loudness or of different pitch, etc.
Limitation on STM capacity only applies if there are no meaningful relationships between separate items When meaningful relationships exist among the items, many more items can be held in STM.
Psych 355, Miyamoto, Spr '18
Some Issues re Measures of Memory Span

32. Some Issues Regarding Measures of STM Capacity Limits
The preceding examples use low-meaning stimuli. Would the results differ if we used stimuli with more meaning?
Example: Waiter or waitress taking a dinner order:
I'll have the mushroom soup, the filet of sole with green beans, and rice. (14 words)
I'll have a ceasar salad, the flank steak medium rare, carrots and peas, and mashed potatoes. (16 words)
I'll have .....
Answer: Yes, the results are different when the stimuli are meaningful. How should we interpret this? (See next slide).
Psych 355, Miyamoto, Spr '18
Chunking & Recoding

33. STM Capacity Limits Apply When Stimuli Are Unrelated
The capacity limit, 7 ± 2, applies to sequences of stimuli ....
that do not have an internal organization.
Example (no internal organization):
EGG, PEN, FOG, CAR, BELT, FLY, ....
Example (has internal organization):
YESTERDAY I WENT SHOPPING FOR A NEW COAT I WANTED A WARM COAT THAT HAS A HOOD, ....
"Chunk" – a larger unit of information built out of related smaller units.
"Recoding" – the cognitive process of combining basic pieces of information into larger chunks. Sometimes recoding involves a change in representational format (change in code).
Psych 355, Miyamoto, Spr '18
Example of Chunking – Animals List

34. south north right father mother son left west east back front daughter
Example of Chunking
Your Task: Remember the following 12 words:
Can you remember the words in the list?
south
north
right
father
mother
son
left
west
east
back
front
daughter
Psych 355, Miyamoto, Spr '18
Display the Array of Words: Comment re Chunking

35. Example of Chunking Can you remember the words in the list?
Reciprocal relations:  directions of a compass  orientations relative to one's body  roles in a nuclear family
The 12 words can be grouped into 3 chunks.
north
front
father
south
back
mother
east
left
brother
west
right
sister
Psych 355, Miyamoto, Spr '18
Chunking in Everyday Experience - END

36. Chunking in Everyday Experience
Typically everyday experience is meaningful. Not like trying to remember a series of unrelated digits in the lab!
In everyday experience, people constantly reorganize the current information in terms of related general knowledge.
In a very unfamiliar situation, you may feel overwhelmed with information overload – you aren’t able to chunk effectively in the unfamiliar situation.
Psych 355, Miyamoto, Spr '18
Recoding

37. Recoding
"Recoding" – Changing the representational format (change in code)
Recoding of information in STM can affect ability to retain information in STM.
Psych 355, Miyamoto, Spr '18
Example of Recoding: Story --> Image

38. Example of Recoding
"It is a cold but sunny winter day. You are looking across Drumheller Fountain. Mt. Rainier is visible in the distance. Two children are playing with a ball next to the fountain. They accidentally throw the ball into the water."
If you formed a mental image of the situation, then this is an example of recoding (changing from the verbal format to an image format).
Recoding involves changing the cognitive “code."
Recoding can increase the amount of information that one can retain in STM by putting it into a form that is more easily retained, e.g., changing verbal information into a mental image.
Psych 355, Miyamoto, Spr '18
Codes in STM & LTM: Phonological, Visual, Semantic Codes

39. Codes in Short-Term & Long-Term Memory
A "code" is a format in which information is represented in the cognitive system. (Not the same as the "neural code")
Phonological codes – words represented as sequences of sounds.
Visual codes – mental imagery, diagrams, perceptual memories
Semantic codes – meanings.
Short-term memory (STM) and long-term memory (LTM) use all of these codes plus possibly others that are not listed here.
Particular tasks may be biased towards one kind of coding.
Next: Evidence for different types of mental codes. This evidence presented here is just a taste – later lectures will present much more evidence.
Psych 355, Miyamoto, Spr '18
Evidence for Phonological Codes

40. Evidence for Phonological Codes
Phonological codes (representing words in terms of the sound of the words)
Conrad (1964): People who are asked to remember visually presented letters, make mistakes that confuse a correct letter with similar sounding letters.
Example: Suppose you are asked to remember AFTR. (The letters are presented visually one after the another a screen.)
Common mistake: ASTR or AFPR
Notice "S" sounds like "F" and "P" sounds like "T".
The letters were presented visually, so the effect of sound similarity is due to the way the subject represents the stimulus, and not the stimulus alone.
Psych 355, Miyamoto, Spr '18
Evidence for Visual Codes – Mental Rotation Studies

41. Evidence for Visual Codes: Shepard's Mental Rotation Experiments
TASK: As quickly as possible, decide whether the two figures shown to the right have the same or different shapes.
Response time for "identical" figures is a linear (straight-line) function of the angle of rotation between the figures.
Easy to explain if subjects are rotating a mental image.
Hard to explain if mental representation is exclusively propositional.
The mental rotation experiment which is used as an example in this lecture is described in Goldstein pp. 134 – The main point of this example is that the most plausible explanation for the result is that subjects create a mental image of the geometric figure which they manipulate (rotate) in working memory in order to determine whether the figures are congruent or incongruent. This is evidence for image-like representations in STM.
Response Time
Angle of Rotation
Psych 355, Miyamoto, Spr '18
Mental Rotation Experiment - Interpretation

42. Evidence for Visual Codes: Shepard's Mental Rotation Experiments
Result is easy to explain if we assume that subjects are rotating a mental image.
Results are hard to explain if mental representation is exclusively propositional.
“Propositional representation” = Symbolic code like human language or a computer language.
Easy to explain if subjects are rotating a mental image.
Hard to explain if mental representation is exclusively propositional.
Response Time
Angle of Rotation
Psych 355, Miyamoto, Spr '18
Semantic Codes

43. Semantic Codes
Confusions between long-term memories are usually based on similarity of meaning rather than on similarity of sound or appearance.
Example: Suppose you must remember the following words DOG, PONY, WOLF, ELEPHANT, PENCIL, WHALE
Recognition memory test: Did the list contain "PONY"? Did the list contain "EAGLE"?
Later you are more likely to say "Yes" to "HORSE" than to "LOG." (Intrusion Error: False recognition due to similarity of meaning)
Later you are more likely to say "No" to "PENCIL" than to "WOLF." (Omission Error: False rejection due to dissimilarity of meaning)
Semantic codes also play a role in STM but these examples are more complicated.
* Proactive interference is an example of an effect of semantic coding on STM.
Psych 355, Miyamoto, Spr '18
Summary re Codes

44. Wednesday, 18 April, 2018: The Lecture Ended Here
Psych 355,, Miyamoto, Spr '18

45. Summary re Memory Codes
Recoding: Changing the code in which information is represented, e.g., changing from a phonological code to a visual code.
The phonological code is the primary code for STM.
The semantic code is the primary code for LTM.
Other codes are also used in STM and LTM, e.g., visual code.
Some tasks are easier to perform by using one type of code or another.
Recoding can sometimes help to overcome capacity limits of STM.
Psych 355, Miyamoto, Spr '18
Chess Masters: Example of Chunking & Recoding