1. Chapter 6 Perception

2. 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

3. 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

4. Figure 6.1

5. 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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7. 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

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

9. 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

10. 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

11. 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

12. 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

14. 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

15. 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

16. 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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18. 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

19. 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

20. 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