Transcript Chapter 6 Perception

Chapter 6
Perception
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
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
Figure 6.1
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
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
• An infant on the edge of a visual cliff, being lured to cross the “deep”
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/mother’s voice
• Lose sensitivity to sounds not needed for
home language
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 mother’s smell
• Mothers can identify their newborns by smell
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
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 months=Critical/Sensitive period
• Infant cataracts result in blindness
• Delayed understanding after cochlear
implants
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
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
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
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
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