PSYC 2450- CH 7: Sensation, Perception & Learning
Sensation- detection of stimuli by the sensory receptors and the transmission of this
information to the brain.
Perception- process by which we categorize and interpret sensory stimuli
Early Controversies About Sensory & Perceptual Development
• Empiricists believes children are born as blank slates and we have to learn to
interpret everything through experiences- including our senses. (William James)
• Nativists say that newborns are born with many abilities already there (Emmanuel
Kant, Rene Descartes)
Enrichment Theory- (Piaget) theory specifying that we must add to sensory stimulation
by drawing on stored knowledge in order to perceive a meaningful world.
Differentiation Theory- (Eleanor Gibson) theory specifying that perception involves
detecting distinctive features or cues that are contained in the sensory stimulation we
Distinctive Features- characteristics of a stimulus that remain constant; dimensions on
which two or more objects differ can be discriminated (sometimes called invariances or
Research Methods Used to Study the Infant’s Sensory and Perceptual Experiences
• Researchers have devised methods for understanding what infants might be
sensing & perceiving:
The Preference Method-method used to gain info about infants’perceptual abilities by
presenting two (or more) stimuli and observing which stimulus the infant prefers.
• Used to see if infants could discriminate visual patterns- learned that infants
prefer patterned stimuli
• Shortcoming- if infant shows no preferences, it’s not clear if they failed to
discriminate between them or if they found them equally interesting.
Habituation- decrease in response to a stimulus that has become familiar through
• If infants stop responding to stimuli it tells us that they recognize them
• One stimuli is presented until the infant stops responding to it (habituates) & then
a second stimulus is presented and if the infant differentiates between the two
stimuli he will attend closely to it & show a change in respiration or heart rate:
Dishabituation- an increase in responsiveness that occurs when stimulation changes.
• Researchers must pay careful attention to the familiarization timeline being
The Evoked Potentials Method- an evoked potential is a change in patterning of the
brain waves that indicates that an individual detects (senses) a stimulus The High Amplitude Sucking Method- a method of assessing infants’perceptual
capabilities that capitalizes on the ability of infants to make interesting events last by
varying the rate at which they suck on a special pacifier.
• The pacifier enables the infants to exert some control over the stimulus- infant can
make the stimulus last by producing higher amplitude sucking (based on baseline
Infant Sensory Capabilities
• Young infants can hear well- even newborns can discriminate sounds that differ in
loudness, direction, duration & frequency
• Infants prefer their mother’s voice to others
• Sensitive to phonetic contrasts in speech
Phonemes- smallest meaningful sound units that make up a spoken language.
• Infants less than a week old can detect differences between the vowel sounds i
• 3-6 month old infants are better than adults at perceiving certain phonemes not a
part of their language- allows them to learnANY language they are exposed to.
• They soon learn to recognize words they hear often
• Even mild hearing losses may have adverse developmental effects
• Otitis Media- common bacterial infection of the middle ear that produced mild to
moderate hearing loss.
Taste, Smell & Touch-
• Babies are born with taste preferences- prefer sweet
• They avoid unpleasant smells
• Soon come to recognize mother’s odour if they are breastfed
• They’re also sensitive to touch, temperature & pain
• Least mature of newborn’s capabilities
• Changes in brightness will elicit a subcortical pupillary reflex which shows they
are sensitive to light
• Can discriminate some colours
• Tracks moving targets
VisualAcuity- a person’s ability to see small objects & fine detail
• Don’t see fine detail well- distance vision is about 20/600
• Objects all seem blurry to them because they have trouble accommodating
(changing the shape of the lens to bring things into focus)
• Improves rapidly over first 6 months
Visual Contrast- amount of light/dark transition in a visual stimulus
• Infants require more of this to see
• Develops quickly in the first year • For the first two months babies are “stimulus seekers” who prefer moderately
complex, high contrast targets- preferably ones that move
• Between 2-6 months of age they begin to explore visual targets systematically,
become increasingly sensitive to movement, and begin to perceive visual forms &
• By 9-12 months infants can construct forms from small cues.
o display some size constancy
o they lack ste