Pattern Recognition cont.

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Pattern Recognition (cont.)
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Auditory pattern recognition

• Stimuli for audition is alternating patterns of
  high and low air pressure called sound waves
• The bigger the difference between high and low
  pressure the louder the sound is perceived to be
• The number of cycles per second determines tone
• Humans can hear sounds as low as 20 cycles/sec
  and as high as 20,00o cycles/sec
• Other animals have a greater range of hearing,
  but humans discriminate between sounds and
  interpret sound better and more quickly
• Speakers produce a continuous string of speech
  sounds that listeners easily break into separate
  words

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Echoic or auditory sensory memory

• Similar to visual sensory memory in many ways
• Definition brief memory system that receives
  auditory stimuli and preserves them for some
  amount of time
• Since hearing is temporal event, you would not be
  able to understand auditory information if it
  disappeared immediately

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Experiments demonstrating echoic memory

• 3 eared man study
• 3 auditory stimuli (letters or numbers) presented
  to the left ear, 3 stimuli to the right ear, and
  3 stimuli to both ears
• Subjects immediatelyasked to report all the
  stimuli they could remember hearing
• Reported about 4 of the 9
• Presented with stimuli again and asked either
  what were the 1st, 2nd or 3rd stimuli you heard
  partial report
• Subjects more accurate, over 5 recalled, but not
  as accurate as Sperlings measure of visual
  sensory memory covered last week though echoic
  memory seemed to last longer

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Does echoic memory fade?

• Subjects presented with a list of 9 numbers, 2
  numbers per second
• Silent vocalization group read the numbers a
  purely visual presentation
• Active vocalization group read the numbers out
  loud as they were presented
• Passive vocalization group- read the numbers and
  listened to a tape recording of someone reading
  the numbers

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Results

• Subjects in all groups remembered about 20 of
  numbers in the beginning of the list and about
  50 in the middle of the list
• The passive and active vocalization groups
  remembered 90 of the last item while the
  nonvocalization group remembered 50
• Suggests that the vocalization groups recall was
  assisted by a still present memory trace in
  echoic memory
• Echoic memory traces do persist over time, but as
  indicated by decreased memory for early items,
  the memory trace fades over extended time

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Does erasure occur in echoic memory?

• Backward masking seemed to erase meory in
  visual sensory memory
• Previous experiment run again. This time after
  hearing the list, vocalization groups heard eith
  a tone or the word zero
• Told this was a cue to begin recall, actually
  used to see if hearing another word would erase
  the memory of the last item
• Group that heard the tone performed the same as
  before. Group that heard zero decreased accuracy
  to 50 same as nonvocaliztion group
• Conclusion memory of last item was erased.
• Overall conclusion echoic memory similar to
  visual sensory memory, but has a samller capacity
  and a longer duration

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Theories of Auditory pattern recognition

• Largely studied in speech, but some work has been
  done with music
• Template theory we store models or templates of
  sounds, an then compare sounds we hear to sounds
  we have stored in memory.
• Doesnt work any better than it did in visual
  sensory memory.
• Speech sounds do not always sound the same though
  we perceive them as being the same

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Feature detection theory

• We detect basic features of the sound and use
  memory to identify them much more successful
• Clearly shows the importance of context
• Phonetic restoration effect when a speech sound
  is missing or covered with white noise, we fill
  it in and dont notice it missing
• Words are more easily recognized when parts are
  missing if they are in sentences than as isolated
  words

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Haptic pattern recognition

• Use of somatosensory system
• When blindfolded, most people can identify
  objects quickly and accurately using haptic
  (active touch) information
• Exploration of an object with hands does not
  involve random movements

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Object recognition using haptic information

• Begins with enclosing smal object n fingers and
  palm
• Then different kinds of stereotypical hand
  movements called exploratory procedures

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Exploratory procedures

• A lateral motion to determine texture.
• Enclosure to determine global shape and size
• Unsupported holding to determine weight
• Conture following tto determine exact shape
• Applying pressure to determine hardness
• Static contact to determine temperature and
  others

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Examples

• People reported that shape was most important in
  identifying a pencil
• Shape and texture important in identifying a
  crayon
• Shape and size important in identifying a used
  pencil

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Visual and haptic information

• Vision not necessary for these exploratory
  procedures to develop.
• Visual and haptic objective recognition processes
  need to work together
• Using haptic information to identify objects of
  different shapes that are the same texture is
  slow and difficult
• Visually sorting objects that identical in shape
  but differ in temperature or hardness is
  difficult if not impossible