Chapter 6 Perception

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Chapter 6Perception
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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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Methods of Studying Infant Perception

• Habituation Discrimination learning
• learning to be bored
• Preferential looking
• Study of visual acuity
• Evoked potentials recorded as child looks
• Operant conditioning
• R of one stimulus in a pair

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Figure 6.1
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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
• Prefer human face overall

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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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Hearing and Speech

• Humans can hear well before birth
• Newborns discriminate sounds that differ in
  loudness, duration, direction, and pitch
• Two-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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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
• To achieve goals solve problems

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The Adult

• Sensory and perceptual capacities decline
• May begin in early adulthood
• Noticeable in the 40s
• Typical by age 65
• Gradual and minor in the normal person
• 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

• 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 of the lens
• Peripheral vision declines

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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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Other Senses in Older Adults

• Over 70 taste and smell thresholds increase
• Many are not affected at all mostly men
• Also 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

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