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Chapter 5: Perceptual & Motor Development
BASIC SENSORY & PERCEPTUAL PROCESSES
• Sensory and perceptual processes are the means by which people receive, select, modify, and
organize stimulation from the world. Each sense organ translates physical stimulation into nerve
• Perceptual processes are closely linked to motor skills with coordinated movements of the muscles and
limbs. Perception often guides a child’s movement, and movement provides variety in perceptual
• Researchers determine that a baby can distinguish between two stimuli by seeing if their responses are
consistently different to the two, with heart rate, facial expression, head movement, etc.
• Habituation is paying more attention to novel stimuli than familiar stimuli. By presenting the same
stimulus repeatedly and then a novel stimulus, researchers see if the infant responds with habituation or
with new behaviour that demonstrates ability to distinguish the two.
• Faster habituation predicts later intelligence scores
Smell, Taste, and Touch
• Infants have a keen sense of smell, responding with the appropriate facial expressions to pleasant and
unpleasant smells. They can also recognize familiar odours, such as their own amniotic fluid, or their
• Infants differentiate readily between tastes, particularly reacting to sweet substances favourably. They
are sensitive to changes in breast milk that reflect a mother’s diet.
• Pain is subjective, with individuals differing in response to the same stimulus. The infant has developed
pain receptors and nerves capable of transmitting pain. Their behaviour to pain-provoking stimuli, such
as the pain cry (sudden, high-pitched, not easily soothed), increased heart rate, and facial expressions
strongly suggest babies experience pain.
• Contact and sweet tastes with giving sucrose during the painful procedure both sooth and reduce pain
• A fetus can hear at 7-8 months; however, infants do not hear as well as adults. The auditory threshold
is the quietest sound a person can hear, measured in infants by presenting a tone and looking at
reactions such as turning the head or changing facial expressions or activity level.
• Infants hear best in pitches the range of human speech. They can differentiate vowels from
consonants, and recognize their own names by 4.5 months.
• Infants can also distinguish musical sounds and different melodies and rhythms. They can differentiate
from a sequence of notes that they have heard before, from a new one.
• Infants use sound to locating objects in terms of direction and distance. Infants hearing the sound of a
rattle in the dark at 15cm away will reach for it, but not at 60cm away. Using sound to estimate distance,
they change their behaviour.
• Heredity is the leading cause of hearing impairments in newborns; after birth, meningitis, the
inflammation of membranes around the CNS, is. Startle responses to sudden, loud sounds, turning the
head to follow sounds, and imitation of sounds and simple words by 12 months are items to check on if
concerned about hearing problems.
• Children may benefit from mechanical devices such as cochlear implants, lip-reading, and learning sign
Seeing Page 156-180, 25 pages Page 2 of7
• Newborns scan their environment by 2-3 months, though not coordinated since eye muscles not fully
developed for synchronous movement. Newborns only catch 2% of light striking fovea due to shape of
eyes, vs. adult 65%
• Visual acuity is the smallest pattern that can be distinguished dependably, as tested by reading rows
of progressively smaller letters. Infants prefer patterned stimuli over plain stimuli, and with progressively
narrow lines at a certain point they will blend together to appear grey like the plain stimuli.
• To estimate an infant’s acuity, a grey square is paired with a square with different stripe widths. When
infants look at the two equally, it indicates they can no longer distinguish the stripes and have reached
the limit of their visual acuity.
• Newborns and 1-month-olds see at 6m what adults see at 60-120m, but improve to achieve equal
acuity at 8mo. Newborns good at seeing 8-10 inches, optimal distance from mother’s face during feeding
• Contrast sensitivity measures responses to stimuli which vary both in size and contrast. It may be a
better measure of the development of the visual system. Development in this area is more gradual,
equalizing with adults at age 9.
• Colour is detected with cones in the retina, which have varying sensitivities to short-wavelength light
(blue, violet), medium-wavelength light (green, yellow), and long-wavelength light (red, orange).
• Neural circuits for colour perception come online after birth, able to see full range of colours by 3
months. This includes perceiving colours as categories.
Integrating Sensory Information
• Most infant experiences are multimedia events, with much stimulation spanning multiple senses. Infants
can visually recognized an object that they only touched previously, detecting relations between
information presented visually and tactily.
• Infants look longer at novel experiences of video not synchronized with own movements, speech not
synchronized with facial movements, or speech facial movements not synchronized with gender
• It was originally thought that infants must first master perceptual processes in each sense separately
before coordinating and integrating across senses.
• Bahrick & Lickliter: Intensensory Redundancy Theory where infant’s perceptual system is particularly
attuned to amodal information (duration, rate, intensity) present in multiple sensory modes. Perception is
best when information is presented redundantly to multiple senses.
• When infant sees and hears mother clapping, he focuses on information conveyed to both senses over
information only available in one sense.
• Tested with hypothesis that infants will notice changes in amodal information more often when it is
presented in multiple than a single sense. They should detect change more readily from clapping slowly
to quickly if they both see and hear it, than if they only see it or only hear it.
o Only infants who had information in both senses detected the change
COMPLEX PERCEPTUAL & ATTENTIONAL
• By 4 months, infants use cues to determine which elements go
together to form objects. One important cue is motion: elements
that move together are usually part of the same object. One would be surprised if elements moving
together are revealed to be separate objects behind a mask.
• Infants demonstrate this surprise: if revealed to be two pencils, they will look much longer as if trying to
figure out what happened. If one pencil, they look briefly having expected it. Page 156-180, 25 pages Page 3 of 7
• Infants group features together as one object if they have the same colour, texture, and aligned edges.
• Infants master size constancy by 4-5 months, realizing that an object’s actual size remains the same
despite changes in the size of its retinal image as a function of distance
• Infants recognize a bear as familiar when it is seen as smaller at a farther distance, and a larger replica
of the bear that casts the same retinal image size as novel – they respond more to the novel bear.
• Brightness, colour, and shape constancy also exist. They are also achieved in rudimentary form by
• Infants also need to know where objects are; left/right and up/down are easily represented on the
retinal surface, but distance is not.
• Visual Cliff: A glass-covered platform, with pattern appearing directly under the glass on one side, but
several feet below glass on the other. Thus one side looks shallow, and the other has a steep drop-off.
• Infants are placed on the platform, and their mother coaxes the
infant to crawl towards her across the deep side; virtually all
refuse to cross the deep side – this demonstrates depth
• Babies as young as 1.5 months who cannot crawl experience
decrease in heartrate when placed on the deep side, a sign of
interest in a novel stimulus; this demonstrates their ability to
discriminate between the shallow and deep sides.
• At 7 months, the infant’s heartrate would accelerate, as a sign
of fear. This is informed by experience with crawling.
• Kinetic cues is using motion to estimate depth. Visual
expansion is when an object moves closer, it fills a greater proportion of the retina.
• Motion parallax is that nearby moving objects move across the visual field faster than those at a
distance – trees next to the road move rapidly, while mountains in the distance move slowly.
• Retinal disparity from fact that left and right eyes often see slightly different versions of the same
thing. When objects are distant, images appear similar for both eyes; when objects are close, there is
• Pictorial cues include use of linear perspective (lines converge to appoint in the distance, can use
distance between lines as cue), texture gradient (from coarse to finer/less distinct in the distance),
interposition (nearby objects obscure distant objects), and
• 1 month olds look at the outer edges of the face with
highest contrast (chin, top of hair), but 3 month olds focus
on the eyes and lips, which are essential for facial
• Newborns tend to prefer face-like stimuli (arrangement of
two eyes and a mouth) over non-face-like stimuli, and faces
over face-like stimuli. However, preference for tracking a
moving face changes at 4 weeks, when infants start tracking all moving stimuli. Face-tracking may thus
be a reflex for newborns, adaptive to enhance social connection, but taken over by the cortex after 4
weeks. Page 156-180, 25 pages Page 4 of7
• Newborns also prefer attractive over unattractive faces, e