Lecture 2: Motor Development Flashcards
Reflexes
- One of the very first things babies can do (innate)
- Innate, involuntary actions that occur in response to a particular stimulation
- Reflexes are adaptive
Reflexes function
*Function of some is unclear
*E.g. tonic neck reflex: when an infant’s head is turned to the side, their arm on that side extends and the arm and knee on the other side flex (looks like they are fencing).
These reflexes are an indication of proper neurological functionning in babies. but if they stay too long until adulthood = something is wrong.
How long to reflexes last?
- Most reflexes disappear by 2 months of age
- Some don’t like coughing, sneezing, blinking, withdrawing from pain
- Absent reflexes or reflexes that persist for too long can mean the infant has neurological problems
Motor Milestones in Infancy
- Major motor developmental tasks of a period.
- Happen in sequence, rarely out of order.
- Huge individual variation in the ages these milestones are achieved.
What about crawling?
- 7 – 8 months of age: babies begin crawling
- Crawling is not considered a motor milestone (must be achieved or else indicates there is a motor issue).
- Crawling looks very different from kid to kid.
- Many healthy babies never crawl and skip right to walking
- Why do some babies skip crawling?
- Upper body or core weakness
- Hypersensitive to the texture of the floor
- Insufficient opportunity (if the child is not given the oppurtunity to lie on the floor and try it then they wont be able to learn it.
Cultural Differences in Motor Development
*Average ages of milestones are based on WEIRD samples, but most infants in the world are not
* Only 15% of the world’s population is WEIRD (western educated industrialized rich democratic - US, CAN and a bit of europe)
*Cultural practices lead to individual differences in when motor milestones are achieved
Example 1: Culture and Sitting
- Huge cross-cultural differences in how long 5-month-olds can sit independently
- Why?
- Related to where infants’ are placed to sit.
- Earlier independent sitting in countries where infants spent more time in places with less postural support (e.g., ground)
- Later independent sitting in countries where infants spent more time in places with lots of postural support (e.g., child furniture or being held)
- Related to where infants’ are placed to sit.
- How much time an infant spends in places with less postural supports impacts when they’ll be able to sit independentlt
Example 2: Culture and Encouragement of Motor Skills
*Motor milestones are affected by how many opportunities infants have to practice and how much motor development is actively encouraged
* E.g., in some countries, some infants are actively discouraged from crawling because of safety or hygiene concerns so crawl later or never crawl (not spending lots of time on ground)
*e.g., urban China
- E.g., motor exercises in sub-Saharan Africa
*Infants are more advanced in motor skill development than kids in North America
Motor Exercises
When baby is born they are experiencing stretching movements and exercises, africa
- leads to kids achieving their motor milestone earlier.
Example 3: Culture, Diapers and Walking
- Diapers affect infant walking
*Infants show more mature walking when naked vs. when wearing a diaper (more mature walking = narrower and close together steps). - All infants were used to wearing a diaper
*Diapers may contribute to cross-cultural differences in walking
Implications of Cultural Difference
*Context plays an important role in motor development
* Differences in the course of motor development reflect the contexts in which infants are developing
Mechanisms Behind Motor Development
*Motor development is governed by complex interplay between numerous factors:
* Brain maturation (used to think it was purely about this)
* Increases in physical strength
* Physical abilities, like posture control and balance
* Perceptual skills
* Change in body proportions and weight
* Motivation
*All these factors contribute to individual differences in motor development
The Role of Weight Changes
- Infants are born with stepping reflex that disappears at 2 months but then start stepping again between 7-12 months of age when learning to walk
*Why does stepping reflex disappear? (used to think it was about brain maturity). - Hypothesis: Infants gain weight faster than they build leg muscles and thus have insufficient strength to lift heavier legs.
- gaining weight faster than building muscles…not enough muscle to lift their weight.
The role of weight changes (evidence)
***Evidence: **
* Infants who no longer show stepping reflex resumed stepping when placed in a tank of water
* buoyancy of water supported weight.
- Shows that disappearance of stepping reflex is due to weight change and not just cortical maturation
The Role of Motivation
*Infants are highly, intrinsically motivated to explore and learn:
* Persistence despite failing (get back up and go again)
* Continue to practice new skills even though they possess skills that are more efficient that could accomplish the same goal
- e.g., practice walking even though they know how to crawl
* Look delighted when practicing new skill
* Most learning happens in the first year of life
The role of motivation (study)
*Individual differences in motivation predict when motor milestones are achieved
*Study: Compared low and high motivation infants on when they achieved motor milestones
* Low motivation infants: movements occur 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.
*Highly motivated infants achieved all motor milestones earlier than less motivated infants.
Summary of Motor Development so far
*Infants are born with reflexes, many of which disappear by 2 months
*Motor milestones are achieved in a predictable sequence
*Lots of individual differences due to numerous complex factors
* E.g., culture, weight gain, motivation, et
Implications of Motor Individual Differences
*Level of motor skills at 5 months predicted:
* Intelligence at 4 and 10 years old
* Academic achievement at 14 years old (beginning of HS)
*Findings controlled for parent’s intelligence, supportive caregiving, and quality of home environment
*Suggests that motor development influences cognitive development
Motor Development is Critical for Learning
*Enables active learning about the world (rather than be more passive).
* Allows children to learn by trial and error
- can walk around and explore
- can sit and grab objects to learn about it
*Facilitates development of skills in other domain
Reaching
- 7 months: able to sit independently and to reach for objects
- Has consequences for visual and social development.
Reaching and 3D Object Perception
- Reaching enables object exploration which in turn fosters an understanding that objects are 3D
- when we look at an object, we observe it as a 3D object
- children learn this ability of how 3D objects work by reaching and grabbing a thing to explore it.
Reaching and 3D Object Perception (study)
*Study: Habituation paradigm with 4-7.5 month olds
* Assessed sitting and reaching ability
* Habituation: Presented with rotating object with only 2 sides visible
* Does the infant perceive this shape as a complete 3D object?
- Test: Presented with rotating complete shape beside a rotating hollow shape
Reaching and 3D Object Perception
- If infant saw shape as a complete 3D object, should look longer at incomplete display because novel
-
Results:
- Infants that were more advanced in sitting and reaching were more likely to look at the incomplete display
- Suggests that motor skills development in sitting and reaching fosters 3D object perception.
- Infants that were more advanced in sitting and reaching were more likely to look at the incomplete display
Reaching is helping and fostering 3D object perception.
Reaching and Social Development (study)
*Study: When watching a video of a person placing objects in a bucket, adults and 12-month-olds showed proactive gaze towards the bucket
* Indicates that they understand the person’s intention
6-month olds did not
* Have not yet developed the skilled object reaching and manipulation
* Shows that they did not understand the person’s intention
*Shows that infants’ ability to predict others’ actions relies on them being able to perform these same action (need enough practice of themselves doing it)
