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COGNITIVE PSYCHOLOGY (CONTINUED):Hubel & Wiesel, Sensory Memory

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Cognitive Psychology ­ PSY 504
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Lesson 05
COGNITIVE PSYCHOLOGY (CONTINUED)
Information Processing in Visual Cells
Information processing (of visual information) is done in our visual cortex. Different classical
experiments were conducted to understand how do sensation transform into perception? One
experiment was conducted by Kuffler in 1953. Kuffler studied ganglion cells in order to
understand how sensation transforms into perception and he discovered on-off and off-on
cells. These cells define visual information processing. If the light fell on the centre of retina,
on-off cells were activated, if the light fell on the periphery, off-on cells start firing. In figure of
Ganglion cells there are on-off cells on the left side. On right side there are off-on cells. Lines
indicate the activation of neuron and it also indicating the generation of electrical impulses.
When light fells on centre of retina the on-off cells start firing. When light fells on peripheral
on-off cells are not firing. At this point off-on cells activate. When light is on centre on-off cells
work and off-on cells do not work. When there is illumination on surrounding point on-off cells
become silent and off-cells start work. When there is diffuse illumination both cells firing
slowly. This all is happening at ganglion cells level. Before going visual cortex, the visual
system has started processing. The ganglion cells processing is given in following figure.
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Cognitive Psychology ­ PSY 504
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Hubel & Wiesel
Another important experiment was conducted by Hubel & Wiesel in 1962. They started their
experiment with cats. They used visual cortex of the cat. They showed different stimuli, lights
and shapes to cats and then they viewed cortical cells are more complex. They found that
visual cortical cells responded in a more complex manner than lower cells. They named those
cells bar detectors and edge detectors.
Edge detectors help us to understand where an object ends and other starts. Edge detectors
respond positively to light on one side of line and negatively to light on the other side. And Bar
detectors respond positively to light in the center and negatively to light at the periphery, or
vice versa. Both bars and edges detectors are specific with respect to position, orientation,
and width. That is, they respond only to stimulation in a small area of visual field. Bar and
Edge detectors combine to see a lot of objects as shown in the figure.
David Marr's Work
The David Marr developed a computer model of how information from the on and off cells
could be used to yield a useful analysis of the visual image. He developed a model in which
computer like human beings assimilate on-off cells.
Marr and Hildreth (1980) combined the output of off-on detectors to calculate bars and edges of
various widths and orientations.
In computer system symbolic descriptions were created. Boundaries of objects in the real images
pose a difficult problem in computer vision. This system combines the symbolic description to
identify the contour of an object.
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The following picture is showing different things grass, colorful clouds etc. Human mind detect
different things. Like human mind this computer is made to understand different boundaries of
image.
Sensory Memory
When information first enters the human system, it is registered in sensory memories.
Sensory memory allows us to take a snapshot of our environment, and to store this information
for a short period. Only information that is transferred to the other level of memory will be
preserved no more than for a two seconds. Sensory memory holds a short impression of sensory
information even then the sensory system does not send any information anymore. There are 5
basic senses. These are:
1. Vision
2. Hearing
Most of the work has focused on vision and hearing. This is because technology is also
quite advance in hearing and vision like camera, microphone and computers etc.
Computer can receive voice command and also can produce speech.
The others are:
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3. Smell
4. Taste
5. Touch
Visual Sensory Memory
Iconic Memory
It can store a great deal of memory only for a very brief period of time. In human experimentation,
the subject is made to sit and is asked to look at a screen, a computer screen normally. A dot is
shown on the screen with blank white screen (do is located in the center) and the subject is asked
to focus on the dot. Instead of dot, a set of letter is presented at that fixed point, where the subject
is focusing. After a very brief period letters (stimuli) are removed.
Subjects are asked to report items. Subjects normally reported only 4-5 items out of 12 letters.
The set of stimuli is following
Sperling's partial report procedure
An experiment was conducted by Sperling in the field of visual sensory memory. In that
experiment the same array of letter was presented to the subjects but the subjects were
asked to report the letters according to the cue (a beep in this case an auditory cue). After
the array was turned off, a tune was sounded high, medium or low.
High tone cue for reporting the top row
Medium tone cue for middle row
Low tone cue for Bottom row
Better performance
High tone ­ HBST (subject to report the first row)
Medium tone ­ AHMG (subject to report the second row)
Low tone ­ ELWJ (subject to report the third row)
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Subjects reported at least 3 out of 4 letters, no matter whether it was on top row or middle row or
bottom row. It was very significant. Because the subject did not know beforehand which row will
be cued, they had to have three letters from each row available to them. So they had at least 9
out of 12 letters available in their visual memory
Sperling's method was called the partial-report procedure.
The decay in visual memory
Sperling also varied the length of the delay between the offset of the display and the tone. As the
delay increases to 1 second, subjects' performance decays back to the original whole-report level
of 4 or 5 items. As the graph is showing. It indicates our visual memory lose most of the
information in one second.
The decay in visual memory
.
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The criticism on this experiment was that it is an artificial or laboratory phenomenon. It is not
related to real life vision.
Sperling's experiments indicate the existence of a brief visual sensory store- a memory that can
effectively hold all the information in the visual display. We receive a lot of visual information from
our surrounding but this all store in our visual sensory memory for a very brief period. That
information receives attention, stored in our memory other is lost.
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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