1. Chapter 6 Perception

2. 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

3. Vision
Present at birth
Detect changes in brightness
Visually track moving objects
By 4 months can discriminate colors
Visual acuity at about 8 inches
Prefer contour, contrast, & movement
Prefer complex over simple patterns
Prefer human face over all

4. Figure 6.1 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.
Figure 6.1

5. 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

6. 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

7. 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

8. 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

9. Integrating Sensory Information
Vision & touch, vision & hearing are interrelated within the first month
Cross-modal perception: previously seen objects hidden a bag are identified by touch
Very early perceptual abilities are evidence for “Nature”
Sensory system requires stimulation to develop normally
First 3-4 months considered critical

10. 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

11. 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

12. 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

13. 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

14. 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 sever pain