CHAPTER 6 PERCEPTION

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CHAPTER 6PERCEPTION
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Learning Objectives

• What are the views of constructivists and
  nativists on the nature/nurture issue as it
  relates to sensation and perception?

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Nature and Nurture

• Constructivists (Nurture)
• Perception is constructed through learning
• Declines due to environmental influences
• E.g., disease, loud noise etc.
• Nativists (Nature)
• Perception does not require interpretation
• Declines are universal, due to aging

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Learning Objectives

• How are perceptual abilities of infants assessed?
  
• What are infants visual capabilities?
• What sorts of things do infants prefer to look
  at?

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Methods of Studying Infant Perception

• Habituation Discrimination Learning
• Learning to be bored
• Preferential looking
• Duration of looking at one of a pair
• Evoked Potentials recorded as child looks
• Operant Conditioning
• R of one stimulus in a pair

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Vision

• Present at birth
• Detect changes in brightness
• Visually track moving objects
• By 4 months can discriminate colors
• Visual acuity at about 8 inches
• Visual accommodation 6 to 12 mo
• Color vision mature at 2 to 3 mo
• Prefer contour, contrast, and movement
• Prefer complex over simple patterns

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• Researchers must devise special ways to assess
  infants perceptual abilities. Here, an
  experimenter and camera record how much time the
  infant looks at each stimulus. The visual
  preference test was pioneered by Robert Fantz in
  the early 1960s.

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• In a series of studies, Cassia, Turati, and
  Simion (2004) showed that newborns prefer an
  upright face over an upside-down one (A) and
  prefer a top-heavy configuration over a
  bottom-heavy one (B), but do not show a
  preference for an upright face when paired with a
  top-heavy configuration.

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Vision 2

• Depth perception
• Newborns appear to have size constancy
• The visual cliff Gibson Walk (1960)
• A crawler (7 mo) will not cross the cliff
• Can perceive the cliff by 2 months
• Fear of drop-off requires crawling
• Infants as Intuitive Theorists able to make
  sense of the world

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• An infant on the edge of a visual cliff, being
  lured to cross the deep side.

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Video Vision
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Learning Objectives

• What are the auditory capabilities of infants?
• What do researchers know about infants abilities
  to perceive speech?
• What are the taste and smell capabilities of
  infants?
• To what extent are infants sensitive to touch,
  temperature, and pain?

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Hearing and Speech

• Humans can hear well before birth
• Newborns discriminate sounds that differ in
  loudness, duration, direction, and pitch
• Two- to 3-month olds distinguish phonemes
• Eimas (1985) Ba Pa studies
• Newborns prefer female/mothers voice
• Lose sensitivity to sounds not needed for home
  language

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Taste and Smell

• Newborns can distinguish between sweet, bitter,
  and sour tastes
• Show a clear preference for sweet
• Facial expressions reflect taste
• Cry and turn away from unpleasant smells
• Breast-fed babies recognize mothers smell
• Mothers can identify their newborns by smell

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Touch, Temperature, and Pain

• Sense of touch ( motion) before birth
• Useful for soothing a fussy baby
• At birth sensitivity to warm and cold
• Clearly sensitive to painful stimuli
• Do babies require anesthesia for surgery?
• More harm from stress of pain
• Recommended for circumcisions

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Learning Objectives

• To what extent can infants integrate their
  sensory experiences?
• What is an example of cross-modal perception?
• What role do early experiences play in
  development of perceptions?
• What factors contribute to normal visual
  perception?
• What changes occur in attention throughout
  childhood?

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Integrating Sensory Information

• Senses interrelated within the first month
• Cross-modal perception previously seen objects
  identified by touch alone
• Nature Very early perceptual abilities
• Nurture Sensory system requires stimulation to
  develop normally
• First 3-4 monthsCritical/Sensitive period
• Infant cataracts result in blindness
• Delayed understanding after cochlear implants

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The Development of Attention

• From infancy on
• Attention span increases
• More able to concentrate on a task
• Attention becomes more selective
• Able to ignore distractions
• More systematic perceptual searches in order to
  achieve goals solve problems

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Learning Objectives

• How can hearing loss be minimized across the
  lifespan, beginning with adolescence?
• What changes occur in visual capabilities and
  visual perception during adulthood?
• What changes occur in auditory capabilities and
  speech perception occur during adulthood?
• What changes occur in taste and smell, and in
  sensitivity to touch, temperature, and pain
  during adulthood?

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The Adult

• Sensory and perceptual capacities decline
• May begin in early adulthood
• Noticeable in 40s Typical by age 65
• Gradual and minor in normal adults
• Compensation gradually increases
• Sensory threshold point at which the least
  amount of a stimulus can be detected
• Increases with age

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Sensory/Perceptual Problems

• Sensory thresholds rise with age
• Vision
• By age 70 9/10 wear corrective lenses
• 1 in 4 will have cataracts
• Pupil less responsive to light
• Dim lighting is problematic
• Dark and glare adaptation difficult
• Presbyopia Middle age glasses
• Thickening lens poor near vision

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Other Visual Problems

• Retinal Changes cells die, no longer function
• Age-Related Macular Degeneration
• Loss of center visual field, blurry vision
• Loss of Peripheral Vision (Tunnel Vision)
• Retinitis Pigmentosa (RP)
• Deterioration of light-sensitive cells
• Glaucoma increased eye-fluid pressure
• Damages optic nerve

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Attention and Visual Search

• Selective attention declines
• More easily distracted from task
• Attend to irrelevant cues
• Novel, complex tasks more difficult
• Familiar and well-practiced skills remain

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Hearing/Speech in Older Adults

• Most have at least mild hearing loss
• Presbycusis loss of high-pitched sounds
• More common and earlier in men
• Some difficulty with speech perception
• May be cognitive or sensory
• Background noise a problem
• Novel and complex tasks problematic

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Speech Perception

• Dependent on hearing abilities
• Also cognitive processes
• Attention, memory
• Listening conditions important
• Background noise problematic
• Novel and complex tasks problematic
• Familiar conditions allow use of contextual cues

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Other Senses in Older Adults

• Over 70 Taste and smell thresholds increase
• Many are not affected at all Mostly men
• Affected by disease and medications
• Loss of enjoyment of food may cause malnutrition
  in older adults
• Less sensitive to touch and temperature
• Less sensitive to mild but not severe pain