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Perceptual and Motor Development

34 important questions on Perceptual and Motor Development

What invention demonstrates how difficult our perceptual system is?

i-Cub: a robotic simulation of human perception and action

Compared to this, the human brain solves perceptual problems much faster and much more reliably than the best robotic systems

How does perception develop post-natal? What do these changes depend on?

- minor changes in the structure and function of sensory organs e.g. eyes and ears
- major changes in the structure and function of sensory brain areas

= these changes depend on sensory experience

What are the 5 major post-natal developments that infants go through?

1. Newborn abilities and subsequent development
2. Vision: basic properties
3. Vision: faces and objects
4. Perceptual narrowing
5. Perception and action

p. 125 developmental textbook - the major changes that infants undergo in the first year of life are (1) the ways they are able to act on personal stimuli (2) reducing the number of perceptual discriminations they make (e.g. tuning into their first language rather than discriminating between phonemes in different languages)

Different parts of vision develop at different times. Rank the visual perceptual modalities from early to later development.

*From more basic earlier developing to more complex, later-developing*

1. visual acuity, contrast sensitivity, colour perception
2. perception of global form and motion
3. object and face recognition
4. vision for action

How can we study perceptual abilities in infants? (2 methods)

1. Behaviour - the Teller Acquity Chart = shows that visual acquity develops in the 1st year of life.

2. Brain activity e.g. EEG

What are 3 methods of assessing newborn abilities and subsequent development?

Patterns of looking
Physiological responses
Brain activity

What are 3 basic properties of vision?

1. eye movements
2. visual acuity and contrast sensitivity
3. development of orientation processing, motion processing, and binocularity (behaviour and EEG + neuronal mechanisms)

Why do eye movements take time to mature?

Development of eye movements depend on brain development guided by visual experience (more info last slide on p. 2 of notes)

In what 2 ways can eye movements fail to develop normally?

1. failure for eye movements to develop proper vergence (both eyes converging on the same target) and nystagmus (unsteady fixation)

2. can result from poor visual experience (e.g. blurred vision in one eye)

What is meant by visual acuity and how is it measure in adults?

The finest pattern he/she can see
Often measured by optician's letter chart in adults

How can development of acuity and contrast sensitivity be explained?

- not well explained by physical changes in the eye
- explained by experience-dependant changes in neural connectivity i.e. LGN to V1 (lateral geniculate nucleus to primary visual cortex)

In what way can their be a permanent loss of acuity and contrast sensitivity?

When there is a visual deprivation in infancy - because neurons in V1 do not acquire connections to inputs from the affected eye

What experiment demonstrates the development of visual acuity in newborns?

Maurer & Maurer, 1988

- at 1 week can only discriminate black stripes from a grey background when they are a foot away. Any further than this = they only see a uniform grey
= this is only one-thirtieth as fine a discrimination as an adult can make.

(p.127 social psychology textbook)

How can the development of orientation processing, motion processing, and binocularity be measured through behaviour and EEG?

VEP = visual evoked potential
- this is an EEG method to assess whether neurons are firing in response to a specific visual change e.g. a change of orientation

(more info 3rd slide 4th page)

What are the neuronal mechanisms regarding development of orientation processing, motion processing and binocularity, and how do they work?

1. Cortical cells - orientation selectivity in cortical cells via experience-dependent development of connections from LGN (Hubel & Wiesel, 1960s)

2. Binocularity (input to cortical cells from both eyes) via experience dependent changes in connectivity

Regarding newborn face perception, what type of faces do they prefer? What experiment is this based on?

Johnson et al, Cognition 1991

Newborns prefer standard faces over scrambled

What is newborn face perception likely driven by? Why is this? How does this differ from adults?

Because the newborn visual cortex is so immature, newborn face perception is driven by more basic and early developing sub-cortical mechanisms

Adults = face processing include cortical and sub-cortical mechanisms working in parallel

(Johnson et al, Nature Reviews Neuroscience 2005)

What experience demonstrates which aspects of face organisation newborns respond to?

Johnson et al, Nature Reviews Neuroscience, 2005

What changes happen from birth to 12 weeks? What experiment is this based on?

There is a transition from sub-cortical to cortical mechanisms regarding face perception (Mondloch et al. Psych Science 1999)

Are the neural mechanisms underlying perception in infants the same as those of older children/adults? What experiment is this based on?

De Haan et al. 2002

Using EEG, why did they use the comparison between upright & inverted faces?
- all the visual information is the same, so a differential response indicates activity specific to facial processing
- contrast with another upright vs inverted object for further evidence that the activity is specific to face processing

Results:
= specific cortical response in adults which isn't seen in 6month old infants

Conclusion = cortical processing develops with age

Facial preference experiment -p. 134 & 136 - with good discussion

What aspects of object processing develops with age?

- recognising objects (from different viewpoints)
- size and shape constancy (taking into account that the same 3D object has a different 2D projection depending on viewing angle and distance) exps p.132 & 133 developmental textbook
- understanding physical relationships e.g. occlusion
- assumptions about objects e.g. unity/ coherence

What experiment demonstrates the dishabituation method?

Kellman & Spelke, 1983

Infants who habituate to the broken rod display will prefer to look at the broken rod rather than a complete rod
= they know that an object can exist even if they can't see it (therefore if they find that the rod is broken, they will look longer at it because they didn't expect it to be broken

4 months old = perceive the rod as a whole object
newborns = perceive as 2 separate objects

Supporting studies: Slater et al, 1990, 1994, 1996

What is perceptual development and perceptual narrowing?

Perceptual development includes becoming an expert in making subtle discriminations e.g. telling tow faces apart; telling apart phonemes

Perceptual narrowing - while becoming experts in making these important distinctions, infants also lose the ability to make other distinctions e.g. distinguishing phonemes between a variety of languages

What 2 experiments show perceptual narrowing?

Language
Werker & Tees
Results: young infants can distinguish phonemes from different languages; however they lose this ability by 6-12 months and tune into their own language.
Supporting evidence: Eimas et al, 1971

Faces
Pascalis et al. Science 2002
Results: young infants can discriminate both human and monkey faces equally, but by 9 months they respond more to a novel human face than a novel monkey face

Why does perceptual narrowing occur in terms of the brain's resources?

The brain's resources are limited - it will learn distinctions which are important and not those that are not

How flexible and general are infants' learning mechanisms?

Saffran, Aslin, Fisher, 1996
Task: measured statistical learning in infants
Results: infants' ability to rapidly learn the co-occurrence statistics (which items tend to go together) even in completely artificial stimuli

Describe the motor development of a newborn, an infant at 3 months, 6-12 months and 12-24 months.

At birth
- Neonatal reflexes e.g. eye blink, withdrawal reflex, moro reflex, rooting response (some of these disappear in the 1st year of life)

3 months
- holds head steady
- starts to reach for objects (i.e. reaching is more goal directed (Spencer & Thelen, 2000 - p. 152 developmental textbook)

6-12 months
- sitting, crawling, cruising, walking

12-24 months
- walking up steps, running, jumping, throwing a ball

(more info & experiments p. 152 & 153 developmental textbook)

What is a reflex?

Involuntary responses to external stimuli
(examples of permanent and temporary reflexes on p. 147 & 148 developmental textbook)

Describe the development of manual control.

- start of reaching (3 months)
- ballistic reaching with corrections (5-6 months)
- accurate pincer grasp (9 months)

What experiment shows improvements in control of reaching with age?

Matthew & Cook, Child Dev, 1990

Measured the number of velocity peaks in a 6 month old and an adult
Results = more efficient reaching + better control in adults
Conclusion = reaching control develops with age

What underlies the development of reaching?

1. maturation of the motor system allowing for better muscle control
2. development of binocular vision at around 3-4 months for improved perception of where the target and hand are in space
3. development of attention allowing the infant to develop an action goal and disengage from other irrelevant stimuli

When do infants develop locomotion? Why is good locomotion skills needed?

Around 10-16 months, development through childhood

Needed to accurately perceive depths, surface slants and obstacles

How does environmental factors affect sensorimotor development?

Cross-cultural research = a baby's behaviour during the Brazelton scale differ across cultures due to parent-child interaction

Results - superior motor performance by infants in the Gusii community of West Africa in comparison to American babies (Nugent et al., 1991) = this is because of more vigorous handling by caregivers early in the child's life e.g. carrying the child on the mother's sling which strengthens various muscles (Keefer et al., 1991) - p.151 developmental textbook

How can practice affect sensorimotor development?

= improves it

Zelazo and colleagues (1972)
Task: mothers of newborns gave their infants practice in the stepping reflex a few minutes a day
Result: these infants made more walking responses at 2-8 weeks of age + they also walked earlier than a control group of babies who were given no practice

Supporting evidence:
- Zelazo et al., 1988 - babies who were given more practice in sitting for 3 minutes a day were able to sit upright longer than infants in a no-practice control group.
(p. 151 developmental textbook)

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Developmental Psychology

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