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

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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

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

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 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