Lecture 2: Motor Development Flashcards
reflexes
Innate, involuntary actions that occur in response to a particular stimulation
function of reflexes
adaptive, though the function of some is unclear
examples of reflexes
grasping, rooting, sucking, stepping
what reflex has an unclear function
tonic neck reflex
tonic neck reflex
when an infant’s head is turned to the side, the arm on that side extends and the arm and knee on the other side flex
when do reflexes disappear
Most reflexes disappear by 2 months. Some don’t like coughing, sneezing, blinking, withdrawing from pain
absent/persistent reflexes
Absent reflexes or reflexes that persist for too long can mean that the infant has neurological problems
major milestones
Major motor development tasks of a period
when do major milestones happen?
in sequence, rarely out of order
major milestones among infants
There is huge individual variation in the ages these milestones are achieved
when do babies begin crawling?
7-8 months
why isn’t crawling considered a major milestone?
Many healthy babies never crawl and skip right to walking
why do many healthy babies skip crawling?
- Upper body or core weakness
- Hypersensitive to the texture of the floor
- Tonic neck reflex persists
- Insufficient opportunity
what are average ages of milestones based on?
WEIRD samples
WEIRD samples
Western, Educated, Industrialized, Rich, and Democratic
what % of the world’s population is WEIRD?
15%
culture and major milestones
Cultural practices lead to individual differences in when motor milestones are achieved
three examples of cultural practices leading to differences in major milestones
- culture and sitting
- cuture and encouragement of motor skills
- cultures, diapers, and walking
culture and sitting
There are huge cross-cultural differences in how long 5-month-olds can sit independently
why is there so much variety in sitting across cultures?
- Related to where infants are placed to sit
- Earlier independent sitting in countries where infants spend more time in places with less postural support (ex. The ground)
- Later independent sitting in countries where infants spent more time in places with lots of postural support (ex. Child furniture or being held)
what factors affect when infants develop their motor milestones?
- how many opportunities infants have to practice
- how much motor development is actively encouraged
high encouragement for motor development
In some countries, infants are given motor exercises, so they develop motor skills more quickly
Ex. Sub-Saharan Africa
low encouragement for motor development
In some countries, infants are actively discouraged from crawling because of safety or hygiene concerns, so they crawl later or not at all
Ex. Urban China
culture, diapers, and walking
Infants show more mature walking when naked vs. when wearing a diaper. They also show more mature walking in a disposable diaper vs. a cloth diaper
implications of cultural differences
- Cultural practices in one domain can have unintended consequences in another domain
- Context plays an important role in motor development
early theories behind motor developent
motor development is governed by cortical maturation
current theories behind motor development
Motor development is governed by a complex interplay between numerous factors:
- Neural development
- Increases in physical strength
- Physical abilities, like posture control and balance
- Perceptual skills
- Change in body proportion and weight
- Motivation
stepping reflex
Infants are born with a stepping reflex that disappears at 2 months but then starts stepping again between 7-12 months of age when learning to walk
hypothesis for why the stepping reflex disappears
infants gain weight faster than they build leg muscles and thus have insufficient strength to lift heavier legs
evidence for the role of weight changes in eliminating the stepping reflex
- Young infants who still showed stepping reflex stopped stepping when weights were attached to their ankles
- Infants who no longer show stepping reflex resumed stepping when placed in a tank of water
motivation in infants
- Infants are highly, intrinsically motivated to explore and learn
- Persistence despite failing
- Continue to practice new skills even though they possess skills that are more efficient and could accomplish the same goal
- Look delighted when practicing new skills
individual differences in motivation and milestones
Individual differences in motivation predict when motor milestones are achieved
individual differences in motivation study design
compared low and high-motivation infants on when they achieved motor milestones
low-motivation infants
Movement occurs infrequently, prefer activities that require little energy, require lots of stimulation to change position
high-motivation infants
move often, prefer high-energy activity, change position often, do not need clear stimulation to move
individual differences in motivation study findings
Found that highly motivated infants achieved all motor milestones earlier than less motivated infants
why does motor development matter?
- Enables active learning and expands an infant’s world
- Allows children to learn by trial and error rather than just passively observing
- Increases opportunities for learning
- Facilitates the development of skills in other domains, especially vision and social behaviour
motor development and perceiving 3D objects
Reaching enables object exploration, which has consequences for visual development
motor development at 7 months
- Babies can sit independently and reach
- This allows kids to become more familiar with the properties of different objects, including 3D
motor development perceiving 3D objects study aim
Does independent sitting and reaching facilitate an understanding of 3D objects?
motor development and perceiving 3D objects method
habituation paradigm with 4-7.5 month-olds
motor development and perceiving 3D objects habituation paradigm
presented with a rotating object with only 2 sides visible
motor development and perceiving 3D objects study test
presented infants with a rotating complete shape beside a rotating hollow shape
motor development and perceiving 3D objects study hypothesis
If the infant saw the shape as a complete 3D object, they should look longer at the incomplete display because it’s novel
motor development and perceiving 3D objects study results
Infants that were more advanced in sitting and reaching were more likely to look at the incomplete display. Age was not related to where the infant looked
motor development and perceiving 3D objects study takeaway
motor development in sitting and reaching influences the development of 3D object perception
motor development and depth perception
Motor development impacts depth perception
motor development and depth perception study aim
Can babies tell the difference between slopes?
motor development and depth perception study method
Infants were placed in front of walkways with either shallow or steep slopes and encouraged to crawl across
motor development and depth perception study results
- Perception of sloped depended on crawling experience
- Beginner crawlers (about 8 months) confidently went down the shallow slope but also attempted slopes that were too steep
- Experienced crawlers avoided steep slopes
motor development and depth perception follow-up study results
- When these same babies started walking, they made the same mistake as with crawling
- They initially went down slopes that were too steep
They failed to transfer what they had learned about slopes through crawling to walking
motor development and depth perception studies takeaway
infants have to learn through experience how to integrate perceptual information with each new motor skill developed
scale errors
attempt to perform an action on a miniature object that is impossible due to the huge difference in size between the child and the object
when are scale errors present?
until about 2 years
what causes scale errors?
the failure to integrate visual information when action planning
understanding intentions in adults
Adults proactively shift their gaze to the goal of an action when observing somebody performing that action. This indicates that they understand the person’s intention
motor development and understanding intentions study aim
determine if infants can proactively shift their gaze
motor development and understanding intentions study method
used eye-tracking in adults, 12-month-olds, and 6-month-olds. Researchers showed participants a video of a person placing objects into a bucket
motor development and understanding intentions study results
- Adults and 12-month-olds showed a proactive gaze toward the bucket, but 6-month-olds did not
- 6 month-olds have not yet developed the ability to pick up, carry, and drop objects
motor development and understanding intentions study takeaway
infants’ ability to predict others’ actions relies on them being able to perform these same actions
what might contribute to cross-cultural differences in walking?
diapers
