Chapter 6 Perception

1. Chapter 6Perception

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

5. Figure 6.1

6. 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

7. 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

8. 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 • 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

13. 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

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. 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

17. 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