6. Perceptual Development Flashcards
During the early weeks, what are infants’ perceptual abilities?
1) Can distinguish visual forms and sounds. Pefers to follow faces with gaze, than other visual stimuli. Prefers hearing mother’s voice than stranger
2) Poor visual acuity - eye movements are jerky and reactive. Cannot smoothly track moving stimuli or anticipate visual events
At 2 months, what are the infants’ perceptual abilities?
1) Smooth visual tracking develops
- Infants begins to anticipate visual events
2) Occasionally demonstrate ‘sticky fixation’
- Cannot divert their attention away from object
At 4 months, what are infants’ perceptual abilities?
1) Can distinguish a range of colours, shapes, sizes
2) Can discriminate between different faces (both humans and monkeys)
3) Distinguish speech sounds (phonemes) differentiated in both native and non-native languages
4) Sticky fixation disappears
At 6 months, what are infants’ perceptual abilities?
Visual acuity approximates adult vision
At 8 months, what are infants’ perceptual abilities?
1) Shows more interest in distance objects
2) Becomes quiet when others talk
3) Distinguish between questions and declarative statements
4) More visually aware of tiny objects
At 10 months, what are infants’ perceptual abilities?
1) Visually group similar objects
2) Discriminates an object within another
Eg. cookie inside a jar
3) Investigates textures, designs or parts of toys
At 12 months, what do infants no longer discriminate between?
1) monkey faces
2) non-native speech sounds
Which 3 visual abilities are newborns born with?
1) Detect changes in brightness
2) Distinguish movement in the visual field
3) Track faces and objects with their eyes
How do visual abilities support the maturational theory?
Vision is the most deprived sensory modality prior to birth. Newborns’ visual abilities have not been acquired through exposure to the prenatal environment. Yet vision provides the most detailed information about our perceptual environment.
What is visual acuity?
sharpness or clarity in detecting visual details
What is a key physiological limitation of infant vision?
Impaired visual acuity at birth.
Eg. they can’t distinguish between parallel black and gray lines (grating stimulus). Infants see them blur together into a uniform grey.
Why is visual acuity measured in terms of visual angle and not the size of the stimuli?
Presenting stimuli closer to infants helps them as the patterns become larger on the retina.
lower acuity –> Nearer to eye –> larger visual angle
higher accuity –> Further from eye –> smaller visual angle
Visual angle newborns can resolve is about ___ times what adults can perceive.
- Preference for grating patterns as opposed to uniform grey disappears when the visual angle of grating is reduced to 30 times the size adults can resolve
What is the visual preference method? What is it used for?
“If infant spends more time looking at a particular object, shows they can tell that they are different.” Used to determine whether newborn sees and discriminates visual patterns or merely unrelated lines, angles, and edges.
Briefly describe the visual habituation technique.
Habituate the infant to one shape (eg. circle) and then subsequently show the infant new shapes (eg. triangle, star etc.) The infant will show a novelty preference for the new stimuli. Shown that newborn infants can make perceptual discriminations between different visual stimuli.
What is an advantage of the visual habituation technique over the visual preference method?
Can investigate more perceptual discriminations - less subject to intrinsic preferences of infants
What is a key limitation of the visual habituation technique?
Cannot be sure that newborns discriminate between stimuli in the same way as adults. (ie. by comparing configural shape, could be just comparing orientation of lines)
What has eye-tracking studies shown about infants’ ability to differentiate shapes?
Showed that newborn’s gaze was not distributed over the whole triangle as an adult would be. They centred attention on one of the triangle’s angles but sometimes scanned part of an edge in a limited way. Suggests that while certain elements of a complex pattern attract a newborn’s attention, babies do not necessarily perceive the whole form.
What is the practical value of depth perception?
Distinguishing objects from backgrounds
Making accurate reaches towards objects
Which tool was used to investigate if young infants can perceive depth?
“visual cliff” - consisting of an elevated glass platform with the same pattern on the ‘shallow’ side and ‘deep’ side.
What did the visual cliff experiment find out about babies who could crawl? (6-14 months)
They would not cross from shallow to deep side to get to their mothers, even when the mother encouraged the child to do so. Fearing height suggests their innate ability to perceive depth.
What was a way to investigate if younger infants (can’t crawl) could perceive depth?
Placed 1.5 month olds on shallow side of visual cliff and then the deep side, then measured their heart rates.
Their heart rates decreased, indicating interest rather than fear. Difference in heart rate in young infants showed that they could distinguish depth.
What experience was required for infants to develop a fear of heights?
Experience with locomotion. When younger infants who are unable to crawl are provided 30-40 hours of experience in wheeled walkers, they begin to show fear of heights.
What are the 2 different types of depth cues?
Monocular cues
Binocular cues
What are monocular cues? List the 3 types of monocular cues.
Depth cues available even if viewing with one eye
1) Motion parallax
2) Interposition
3) Linear perspective
What are binocular cues? What is a type of binocular cue?
Depth cues available only when viewing with 2 eyes
- Binocular disparity
What is motion parallax?
When seated in moving vehicle, objects close to us move faster across our visual field than objects further away. Helps us judge distance of objects from us
What is interposition?
When one object is closer to us, it covers those that are further away. Tells us which object is closer.
What is linear perspective?
Relative size of position is determined by drawn/imaginary lines
Painters used linear perspective to simulate a sense of depth in their paintings
The manner in which patterns of light fall on the eye from objects that recede in depth
What is binocular disparity?
Arises because of distance between our eyes.
The sense of a 3rd spatial dimension, produced by the brain’s fusion of the separate images contributed by each eye, each of which reflects the stimulus from a slightly different angle
These slight spatial disparities between objects allow us to perceive depth.
Why is it difficult for newborns to rely on binocular depth cues?
Eyes of newborns move in the same direction only about half the time
When do infants start to coordinate both eyes?
3-5 months. Allows them to make more accurate judgments of depth
What are the 2 categories of monocular cues? which one develops first?
dynamic - motion parallax (rely on movement) develops earlier
static - interposition and linear perspective
Which one develops first? Monocular or binocular cues?
binocular cues
What is size consistency? Is this an innate ability?
The tendency to perceive an object as constant in size regardless of changes in its distance from the viewer and the image it casts on the retinas of the eyes. Yes, either innate or acquired very quickly.
What is shape consistency?
The ability to perceive an object’s shape as constant despite changes in its orientation and angle.
Both size and shape consistency may be innate. How do infants achieve this?
Possibly from other monocular cues in the environment
Eg. Size-ratio relations
Scaling objects with respect to their background texture. Can do this even without binocular cues to depth.
How does an early preference for faces show about maturational theory?
Could represent an innate ability to perceive complex patterns like faces
What evidence suggests that face tracking preference is like a motor reflex and governed by subcortical brain areas?
Neural correlates of face recognition in cortical areas of the brain (the N170 event-related potential measured with an EEG net) develop significantly over the first year of life.
What are limitations of newborns’ hearing?
Adults can detect sounds about 10-15 decibels quieter than newborns. Babies are also less sensitive to low pitched sounds relative to higher frequencies
What 2 characteristics of human voice do newborns prefer hearing?
high in pitch with exaggerated pitch contours (ie. motherese/infant-directed speech)
What is the significance for newborns’ preference for human voice?
Plays an important role in language development and development of social relationships
briefly describe development of music perception in infants.
2 months: can distinguish types of musical sounds (eg. piano vs drum)
4-6 months: prefer music composed of common chords
6 months: Can distinguish changes in melodies
Auditory localization in infants take on a ___ shaped development.
u-shaped. Ability seems to wane during 2-3 months because as cortical regions involved in auditory localization develop, initially inhibit the function of subcortical regions.
Briefly describe development of auditory localisation in infants.
1st month - subcortical region
2-3rd month - cortical regions develop, inhibit subcortical regions
4 months - cortical regions take control
6-12 months - Eg. improve ability to determine a sound’s distance, especially when a sound is getting closer
What are the 4 different receptor channels of ‘touch’?
Pressure, temperature, pain, limb position
Which of our body parts have the most receptors?
lips and hands
Classify infants’ responses to different types of touch into positive and negative reactions.
Positive reactions - gentle stroking
Negative reactions
- Sudden changes in temperature/texture
- Uncomfortable pressure on the body
How do newborns discriminate amongst odors?
Show ‘appropriate’ facial expressions in response to whether it is pleasant or aversive.
Eg. Infants less than 12 hours old reacted to odours of strawberry and banana with look of satisfaction, and reacted to odours of fish or rotten eggs with rejection
Are taste and smell preferences innate or learned?
Just because taste and smell preference is evident at birth, doesn’t mean that it is innate. (ie. could still be learned) foetus can learn to like or avoid certain tastes in prenatal environment or immediately after birth.
What is crossmodal perception?
the process of integrating sensory information across more than one modality.
What was Eleanor Gibson’s alternative view on crossmodal perception?
Suggested that newborns can perceive commonalities among the senses from birth. Infant must learn to differentiate between the unimodal aspects of sensory stimulation.
Which infant activity is structured through predictable temporally regulated patterns of activity, and not environmental situation?
Patterns of sleep and wakefulness/sleeping behaviour.
Internal forces regulate our behavior and explain changes in our activity levels
What is infant state?
Recurring pattern of arousal that ranges from alert, vigorous, wakeful activity, to quiet, regular sleep.
Eyes closed, body completely still
Respiration slow and regular
Face is relaxed (no grimacing), eyelids still
What infant state is this?
Regular sleep
Eyes closed
Engages in gentle limb movements and general stirring
Grimaces and makes other facial expressions
What infant state is this?
Irregular sleep
Eyes open and close intermittently Display recurrent rapid eye movements Relatively inactive Respiration regular, but faster than regular sleep What infant state is this?
Drowsiness
Eyes open, can pursue moving objects
Relatively inactive
Face relaxed and does not grimace
What infant state is this?
Alert inactivity.
Eyes open but not alert
Respiration irregular
Frequently engages in diffuse motor activity involving the whole body
What infant state is this?
waking activity.
Makes crying vocalizations
Engages in diffuse motor activity
What infant state is this?
Crying
What is 3 main types of waking infant states?
Quiet
Active
Distressed - fussing and crying
What are the 2 main types of sleeping infant states?
REM sleep
NREM sleep
Describe the changes in amount of sleep of a developing infant.
Newborn sleeps about 13 hours a day (55% of the time)
Sleeping period decrease dramatically over the first year of life
By the end of the first year, it decreases to around 10 hours per day
By 4 weeks, newborns move towards a ‘monophasic’ sleep pattern. What does this mean?
periods of sleep tend to be fewer but longer
By 8 weeks, newborns start sleeping more during the night and less during the day. What is this sleep called?
diurnal sleep
What is REM sleep characterised by?
Eyes darting around in rapid, jerky movements under closed eyelids.
Associated with dreaming in adults
Fluctuating heart rate and blood pressure
What is the possible functional value of REM sleep for adults?
makes you less irritable and more organised during later waking hours.
What is a functional value of REM sleep for infants.
early brain development in infants. Suggested to be self-stimulating, stimulating the infant’s brain and contributing to development of CNS (develop neural connections)
substitute for environmental stimulation immediately after birth when the sensory systems do not receive much external stimulation since infant is less alert
REM sleep in infants decrease with age. The rate of this decrease is dependent on ______.
amount of external stimulation. (contributes to maturation of the CNS)
What are the 3 factors affecting individual differences in sleep patterns during early life?
1) infants’ intrinsic behaviour
2) parental behaviour - less parental intervention, faster development of diurnal sleep
3) role of culture - Western cultures foster diurnal behavior by keeping infants awake during the day and putting them to bed at night.
What are reflexes?
involuntary responses to external stimuli.
What are the 3 possible developmental course of reflexes?
1) remain permanent
2) disappear after first year
3) replaced by voluntary behaviors that baby learns early in life
What is the function of reflexes in infants?
ensure their survival. May also be building blocks for later behaviour.
Eg. eye-blink helps to shield the eyes from strong light
Eg. rooting and sucking reflexes help the newborn to locate and obtain food
What does abnormalities in infant reflexes indicate?
may indicate visual or hearing problems.
May predict abnormal functions later in life
Reflexes that are weak, absent, unusually strong, or fail to disappear when expected to may signal neurological problems
What can reflexes tell us about the newborn?
health, maturity, and capabilities of the newborn
Which scale can be used to assess overall development of the child?
Brazelton Neonatal Assessment Scale
What does the Brazelton Neonatal Assessment Scale assess?
- Sensory and perceptual abilities (eg. orientation to sights & sounds)
- Early learning capabilities (eg. habituation to sensory stimuli)
- Motor development (eg. muscle tone)
- Infant states and ability to regulate them (eg. soothability)
- Signs that brain is properly controlling involuntary responses (eg. startle reflex)
Sudden Infant Death Syndrome (SIDS) aka ‘cot death’ is most common when?
2-4 months
Describe development of hand skills and locomotion skills
Reaching, grasping, and picking up objects
Balancing, crawling, and walking
What do maturation theorists argue about development of sensorimotor behaviours?
Argue that development of higher cortical areas inhibit functioning of subcortical reflex systems. Replaces subcortical reflexes with voluntary and controlled behaviors. Maturationists argue that these invariant sequences of development are due to the unfolding maturational timetable
What are the 2 development trajectories of sensorimotor behaviours?
Cephalo-causal development (head to toe)
- Balancing head on neck
- Sit up straight
- Move legs in crawling, then walking
Promo-distal development (core outwards)
- Torso → arms → elbow → wrist → fingers
Give an example of how environmental factors can affect development of sensorimotor behaviours.
Gusii community of West Africa - infants have superior motor performance on the brazelton scale. Related to the more vigorous handling by caregivers (carrying baby on mother’s body in a sling), strengthening various muscles of infants
What does reaching allow infants to do?
Enables infants to inspect objects, and manipulate them. Influences the way they perceive objects
Describe the development of ‘reaching’ in infants.
3-4 months: Reaches become more ‘goal directed’
5 months: Grasps that anticipate orientation of an object, with changes in the orientation of hand
Describe the development of ‘gripping’ in infants.
months: 4, 8, 12, 18, age 2, age 3
4 months: rely on touch to determine their grip
8 months: rely on vision to preshape their hand
1 years:
Skilled reachers and graspers
Learn to use objects as tools (eg. spoon)
18 months:
Can effectively use objects as tools
Learn to use hand and finger gestures in social communication (eg. pointing)
Age 2: can use their hands skillfully in play (eg. building a tower of blocks)
Age 3: use their hands to scribble with crayons or copy vertical lines on a page
Development of locomotion follows a ______ pattern. Why? (a few reasons)
U-shaped.
Maturation of motor cortex
Emergence of ability to plan sequences of movement
Consequence of watching people walk.
How does the dynamic systems theory explain the u-shaped pattern of locomotion?
Suggests that walking skills are determined by interaction of multiple factors – genetic, environmental, physical (eg. changing shape of the body)
Stepping reflex disappears for 10 months due to physical factors – baby’s legs become too heavy. Size & weight of legs become too heavy for the emerging motor system.
Theory was tested by putting infants on a motorized treadmill with support in an upright position. They immediately performed alternating stepping movements that looked similar to mature walking.
