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 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