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
