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MEMORY:Rate of forgetting, Size of memory set

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Cognitive Psychology ­ PSY 504
VU
Lesson 24
MEMORY
Short Term working memory (continued)
Short term working memory is a kind of memory that we use for functioning, for all our conscious
awareness functioning. It is distinct from long term memory because it is not a store house of
information. It keeps things for a very short time. An important model of short term working
memory was given by Atkinson and Shiffrin.
Rate of forgetting
Information in Short Term Memory is lost rapidly unless it is preserved through rehearsal.
Perhaps the most characteristic feature about information in working memory is that if we do not
do something special to keep it active, its activation will rapidly decay away and we will lose
access to the information.
Peterson & Peterson (1959) conducted an experiment to illustrate the transient character of short
term memory at Indiana University. They had subjects study three consonants (KCB) and then
asked for recall of the letters after various
intervals of time up to 18 seconds. And then had subjects count backward by three during the
retention interval. Thus, following presentation of the letters, subjects might be asked to count
backward by threes as fast as possible from 506, 509, 512 and so on. They asked subjects count
backward until the signal (light).
This diagram is showing the
results.  There  is  retention
interval on X-axis and there is
percent correct on y-axis.
Implications
Peterson
and
Peterson
concluded. Information in STM
decays very quickly. In 18
seconds
subjects
are
performing at less than 20%
accuracy level. But is it decay
or interference?
For giving this answer of this
question Waugh & Norman
(1965)  conducted  a  clever
experiment. They said decay is
due to interference. In their
experiment they presented list of16 single digits. The last digit (probe) had occurred only once
before in the list. The task was to report the letter after the probe. For example the list is ...1,
2,7,6,8, 2 the correct answer = 7. Subject had to listen list and then reported what is the last
number of last word. They varied the number of interfering items. They varied the rate as 1 digit or
4 digits per second. The purpose of varying the rate of presentation was that they thought when
we vary the presentation then we can capture time factor.
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Cognitive Psychology ­ PSY 504
VU
This diagram is showing the results. There is number of items on X-axis and there is Rate on y-
axis. Blank circles show the rate of presentation. One digit per second is showed by empty
circles. Four digits per second are showed by black circle. The difference between black and
white circles is not significant. But when we increase number of interfering items the decay is
increasing. Because of interfering items the short term memory is becoming impaired. They
concluded that loss of memory is due to interference of other task.
A practical experiment for student
Read digits 0-9 in a random order such as 7 3 4 9 6 8 2 to a friend.
Try reading lists ranging from five digits to 10 digits.
And then make a note of how many digits your friend can recall correctly.
Implications
Waugh & Norman (1965) concluded that it is difficult to maintain information in working memory.
It has a limited capacity. Information decays quickly in working memory. If unattended the items in
working memory will rapidly decay away in their level of activation.
Some people gave the idea that there are some slots in working memory. Working memories
have a fixed number of slots?
What is the problem?
We are aware of many things in our environment at the same time. Fixed number of slots is not
the issue. The problem is how to keep things that have disappeared active in the working
memory. The problem is that information rapidly decays in its level of activation.
There are limitations on how many items one can maintain in working memory. Theses limitations
are determined by how many items one can rehearse before they decay away.
Size of memory set
An experiment was conducted by Sternberg in 1969.
In his experiment he presented subjects with a memory set of digits ( 3, 4, 8, 1) to hold in short
term memory. He then presented a test digit, and subjects were required to determine whether it
was in the memory set. He varied the size of memory set from 1 digit to 6.
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Cognitive Psychology ­ PSY 504
VU
This figure is showing the result. There is a nearly linear relationship between memory-set size
and judgment time. The size of memory set slows down judgment time whether the items are
letters, words, colors, and so on, with all kinds of subject populations, and in all kinds of mental
states.
Implications
Sternberg argues that subjects compare target letter with each letter in the set. The time taken by
each comparison is 38ms.
His model was called Serial processing model.
Anderson proposes that target letter is compared with all the letters at the same time; the duration
increases because the activation is spread across letters.
Working Memory: an activation model
The items in working memory are defined by a high level of activation, which enables reliable and
rapid access to them. If unattended the items in working memory will rapidly decay away in their
level of activation. One can maintain items in working memory by rehearsing them and keeping
them in a highly active state. There are limitations on how many items one can rehearse before
they decay.
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Table of Contents:
  1. INTRODUCTION:Historical Background
  2. THE INFORMATION PROCESSING APPROACH
  3. COGNITIVE NEUROPSYCHOLOGY:Brains of Dead People, The Neuron
  4. COGNITIVE NEUROPSYCHOLOGY (CONTINUED):The Eye, The visual pathway
  5. COGNITIVE PSYCHOLOGY (CONTINUED):Hubel & Wiesel, Sensory Memory
  6. VISUAL SENSORY MEMORY EXPERIMENTS (CONTINUED):Psychological Time
  7. ATTENTION:Single-mindedness, In Shadowing Paradigm, Attention and meaning
  8. ATTENTION (continued):Implications, Treisman’s Model, Norman’s Model
  9. ATTENTION (continued):Capacity Models, Arousal, Multimode Theory
  10. ATTENTION:Subsidiary Task, Capacity Theory, Reaction Time & Accuracy, Implications
  11. RECAP OF LAST LESSONS:AUTOMATICITY, Automatic Processing
  12. AUTOMATICITY (continued):Experiment, Implications, Task interference
  13. AUTOMATICITY (continued):Predicting flight performance, Thought suppression
  14. PATTERN RECOGNITION:Template Matching Models, Human flexibility
  15. PATTERN RECOGNITION:Implications, Phonemes, Voicing, Place of articulation
  16. PATTERN RECOGNITION (continued):Adaptation paradigm
  17. PATTERN RECOGNITION (continued):Gestalt Theory of Perception
  18. PATTERN RECOGNITION (continued):Queen Elizabeth’s vase, Palmer (1977)
  19. OBJECT PERCEPTION (continued):Segmentation, Recognition of object
  20. ATTENTION & PATTERN RECOGNITION:Word Superiority Effect
  21. PATTERN RECOGNITION (CONTINUED):Neural Networks, Patterns of connections
  22. PATTERN RECOGNITION (CONTINUED):Effects of Sentence Context
  23. MEMORY:Short Term Working Memory, Atkinson & Shiffrin Model
  24. MEMORY:Rate of forgetting, Size of memory set
  25. Memory:Activation in a network, Magic number 7, Chunking
  26. Memory:Chunking, Individual differences in chunking
  27. MEMORY:THE NATURE OF FORGETTING, Release from PI, Central Executive
  28. Memory:Atkinson & Shiffrin Model, Long Term Memory, Different kinds of LTM
  29. Memory:Spread of Activation, Associative Priming, Implications, More Priming
  30. Memory:Interference, The Critical Assumption, Limited capacity
  31. Memory:Interference, Historical Memories, Recall versus Recognition
  32. Memory:Are forgotten memories lost forever?
  33. Memory:Recognition of lost memories, Representation of knowledge
  34. Memory:Benefits of Categorization, Levels of Categories
  35. Memory:Prototype, Rosch and Colleagues, Experiments of Stephen Read
  36. Memory:Schema Theory, A European Solution, Generalization hierarchies
  37. Memory:Superset Schemas, Part hierarchy, Slots Have More Schemas
  38. MEMORY:Representation of knowledge (continued), Memory for stories
  39. Memory:Representation of knowledge, PQ4R Method, Elaboration
  40. Memory:Study Methods, Analyze Story Structure, Use Multiple Modalities
  41. Memory:Mental Imagery, More evidence, Kosslyn yet again, Image Comparison
  42. Mental Imagery:Eidetic Imagery, Eidetic Psychotherapy, Hot and cold imagery
  43. Language and thought:Productivity & Regularity, Linguistic Intuition
  44. Cognitive development:Assimilation, Accommodation, Stage Theory
  45. Cognitive Development:Gender Identity, Learning Mathematics, Sensory Memory