PSYC 2450 Chapter 7: Chapter 7

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Developmental Psychology Textbook Notes Chapter 7
Early Controversies about Sensory and Perceptual Development
Nature vs. Nurture
Empiricist philosophers believed that an infant was a tabula rasa (blank slate)
who must learn to interpret sensations
William James argued that all senses are integrated at birth, so that sights,
sounds, and other sensory inputs combine to present the newborn with a
“blooming, bussing confusion”
Nativist philosophers such as Rene Descartes and Immanuel Kant took the
nature side and said that many basic perceptual abilities are innate
o Believed that we are born with an understanding of spatial relations
o Infants do not need to learn that receding objects appear smaller or that
approaching objects seem to increase in size; these were said to be
adaptive perceptual understandings that were built into the human
nervous system over evolution
Enrichment versus Differentiation
Second issue: is the coherent reality that we experience through the senses
simply “out there” or to be detected? Or rather do we construct our own
interpretations of that reality based on our experiences?
Both theories argue that there is an objective reality out there to which we
Enrichment theory: theory specifying that we must add to sensory stimulation
by drawing on stored knowledge in order to perceive a meaningful world
o Claims that sensory stimulation is often fragmented or confusing
o Use cognitive schemes to add or enrich
o Cognition enriches sensory experience; knowledge helps construct
meaning from the sensory stimulation we receive
Differentiation theory: argues that sensory stimulation provides all we need to
interpret our experiences
o Detect the differentiating information, or distinctive features that enable
us to discriminate one form of experience from another
o Once children master the perceptual learning, their continuing quest for
differentiating information may soon enable them to distinguish long-nosed
collies from pug-faced boxers or spotted Dalmatians, although they
understand that all these animals are properly labelled dogs
o Information needed to make these finer distinctions was always there in
the animals themselves, and that the children’s perceptual capabilities
blossom as they detect these distinctive features
Sensation: detection of stimuli by the sensory receptors and transmission of this
information to the brain
Perception: process by which we categorize and interpret sensory input
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Research Methods Used to Study the Infant’s Sensory and Perceptual
In the early 190s medical text claimed that human infants were functionally blind,
deaf, and impervious to pain for several days after birth
Were believed to be unprepared to extract any “meaning” from the world around
The Preference Method
A simple procedure in which at least two stimuli are presented simultaneously to
see whether infants will attend more to one of them than the other(s)
Robert Fantz used it to determine whether very young infants could discriminate
visual patterns
o Babies were shown two or more stimuli
o Observer located above the looking chamber recorded amount of time the
infant gazed at each of the visual patterns
o If the infant looked longer at one than the other, it was assumed they
preferred that pattern
Newborns could easily discriminate visual forms, and they preferred to look at
patterned stimulus such as faces rather than at unpatterned disks
Ability to detect and discriminate patterns is innate
Shortcoming: if an infant shows no preferences, it is not clear whether they failed
to discriminate them or simply found them equally interesting
The Habituation Method
Habituation is the process in which a repeated stimulus becomes so familiar that
responses initially associated with it no longer occur
Simple form of learning
As infants stop responding to familiar stimuli, they are telling us that they
recognize them as old hat something they have experienced before
Also referred to as “familiarization-novelty” procedure
To test an infant’s ability to discriminate two stimuli that differ in some way, the
investigator first presents one of the stimuli until the infant stops attending or
otherwise responding to it (habituates)
o Second stimulus is presented
o If infant discriminates this second stimulus from the first, they will
dishabituate attend closely to it while showing a change in respiration
or heart rate
o If they fail to react, it is assumed that the differences between the two
stimuli were too subtle for him or her to detect
Infants display preference when they are familiar but not too familiar with a
When they become very familiar with the original stimulus, they become ready to
move on and will spend less time looking at the familiar stimulus than the
unfamiliar one
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Dishabituation: an increase in responsiveness that occurs when stimulation
The Evoked Potentials Methods
Present the with a stimulus and record their brain waves
Responses to visual stimuli are recorded from the back of the head at a site
above the occipital lobe, and visual are recorded from the side of the head above
temporal lobe
Changes in the patterning of their brain waves, or evoked potential
This evoked potentials a change in patterning of the brain waves that
indicates that and individual detects a stimulus can even tell us whether infants
can discriminate various sights or sounds, because they produce different
patterns of electrical activity
The High-Amplitude Sucking Method
Provides infants with a special pacifier containing electrical circuitry that enables
them to exert some control over the sensory
Whenever the infant sucks faster or harder than he or she did during the baseline
observations, the infants trips the electrical circuit in the pacifier, thereby
activating a slide projector or tape recorder that introduces some kind of sensory
Infant Sensory Capabilities
Soft sounds that adults can hear must be made noticeably louder before a
neonate can detect them
In the first few hours, infants may hear about as well as and adult with a head
Insensitivity to softer sounds could be due to fluids that have seeped into the
inner ear
Neonates are capable of discriminating sounds that differ
At 4-6 months’ infants react to a rapidly approaching auditory stimulus I the same
way that they react to approaching visual stimuli
Reactions to Voices
Particularly attentive to voices, especially high-pitched feminine voices
Mother’s voice?
o Newborns suck faster on a nipple to hear a recording of their mother’s
voice than a recording of another woman
Infants may need to see facial expressions to help them distinguish adult
emotional states
Reactions to Language
Able to discriminate basic speech sounds called phonemes very early
o Smallest meaningful sound units that make up a spoken language
2-3 months old could distinguish consonant sounds that are very similar
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