L6 (motor) Flashcards
Main difference between human development and other animals’
super slow
* born at an earlier stage of development
* have a longer period of dependence
suggests that humans are not precocious
Physical reason for slow human development
humans offset development to experience-expectant plasticity
* cortex gets bigger as we evolve (greater cognitive abilities)
* pelvis gets smaller as we evolve (to walk upright) so baby’s head won’t fit through mom’s pelvis after 38 weeks of development
so we have to be born earlier or brain development has to be delayed longer
Cultural reason for slow human development
development optimized based on experience-dependent plasticity
* coming underdeveloped means that subsequent development can be shaped by input to work best with your environment
i.e. cultural learning
What do growth charts show?
tells you where an infant lies (in terms of weight, height, and head size) relative to average peer of same gender and age
Secular trend in growth chart for weight in babies
i.e. likely to continue moving in same general direction
North American babies are getting even bigger
failure to thrive = below 3rd percentile
Is growth continuous?
No
* babies may not grow at all for days or weeks then grow more than a cm overnight
* nutrition is critical for physical and cognitive growth
e.g. epigenetic effects of malnutrition during pregnancy
Benefits of breastfeeding
- associated with various positive health outcomes in infant and mother (e.g. reduced chest and ear infection, colds, obesity, asthma)
- bonding experience
- free of charge
should breastfeed exclusively until 6 months
Disadvantages of breastfeeding
- hard (and pumping is harder)
- makes it difficult to share childcare labor
- though associated with positive health outcomes, correlation not equal to causation
Examples of newborns’ reflexes
stepping reflex, diving reflex, moro reflex, tonic neck reflex (i.e. superhero reflex), grasping reflex
- moro: reaching out when you feel like you’re falling during sleep
- grasping: can hold up their own weight
- others include patellar, rooting, sucking, babinsky reflexes
Why do reflexes develop in infants?
- allows them to get sustenance (e.g. crawling, rooting, sucking, swallowing reflexes)
- building blocks of later development (e.g. stepping, grasping, crawling)
- useless vestiges from primate ancestors (e.g. tonic neck reflex)
- indication for developmental disorders (e.g. absence or persistence of reflexes)
rooting: baby orients themself in the direction of the touch, which helps them find bottle or breast
2 possible reasons why development of most reflexes follow u-shaped curves
- 2-systems view: reflexes reflect immaturity and reliance on low-level brain systems then get replaced by high-level cortically-controlled abilities
- reflexes remain and only seem to disappear
Why does the stepping reflex disappear at ~2 months?
- negative association between motor development and body size
- babies get fat and their muscles lack strength to move their limbs
Study: can induce stepping reflex in non-newborns by submerging them in water (weight is lighter)
Dynamic systems theory
Esther Thelen
- motor development involves the interaction of many things coming together in the right way
- not just the maturation of a single high-level system or several high-level systems for walking, reaching, etc.
will encounter both regressions and progressions, and tons of practice is required
Gesell’s maturational account
- large longitudinal study that noted when middle class, White American babies tended to reach milestones
- believed that milestones are universally achieved due to maturation of CNS
- developmental variation is genetic
2 problems with the motor milestones approach
- wide cross-cultural variation
- motor development far more continous within kid and far more variable between kids
What is the best predictor of crawling/walking skill?
experience (number of weeks crawling/walking) is a better predictor of crawling/walking skill than age or limb size (important to get you to start)
e.g. infants who belly crawl are better hands-and-knees crawlers at first than those who never belly crawl
Factors that influence walking skill
age, body size, muscle tone, practice, characteristics of the ground, what you’re wearing (e.g. naked babies are more effective walkers than those wearing diapers)
makes walking seem less like a milestone
How does reaching ability develop (at 4-6 months)?
- initially appears completely random with lots of arm flapping (pre-reaching)
- able to reach in the right direction with guidance and when their posture is supported (body directed toward object)
- reaches improve over time
e.g. can anticipate trajectories of moving objects; don’t reach for out-of-reach objects; adjust hand shape for different-sized objects
Development of reach adjustments (at 10-14 months)
- 10-month-olds reach faster for an object to throw than for an object to be used precisely
- 14-month-olds and older have trouble with reach inversions and hand-switching
limited at first and slow to adjust based on what they plan to do with an object
What’s important for tool use?
starts developing at ~9 months
means-ends actions: incorporating multiple steps into achieving a goal
e.g. using a spoon for feeding or a rake for drawing objects closer
Visual or optic flow
- the visual experience of moving through space specifies the direction and speed of movement
- necessary for integrating perception and action
e.g. blind children are delayed in walking (but not crawling) presumably because they don’t get vision + motor experience
The moving room
- tests proprioception (sense of movement and location) and the use of optic flow
- early walkers fall while adults sway and correct their posture
the more experience, the more behavioral flexibility
What kind of experience matters for locomotion?
active feedback but there’s no critical period (can resolve problems with experience)
e.g. passive kittens who are carried around a carousel in a box are unable to link depth perception with motor activity so they wander off visual cliff and don’t blink when objects fly at them
Difference that experience makes in infants on the visual cliff
- infants with only 2 weeks of crawling experience cross while those with 6 weeks of experience avoid the cliff
- 1-month-olds perceive the cliff (heart rate slows) but issue lies in failure to integrate perception and action, particularly perception of affordances
affordances: the relation between their abilities and the environment
Main finding from the veritable cliff
Karen Adolph
experience integrating perception and action is required in every new posture
e.g. scale errors in toddlers like attempting to sit on a tiny chair
Relationship between motor and cognitive development
babies with better motor skills do better at some cognitive tasks
e.g. determining what sounds made by which objects, perceiving objects as 3D
Example of long-term persistence of the relationship between motor and cognitive development
those with more motor maturity at 5 months have greater academic achievement at 14 years
- motor maturity assessed via how they behave while lying on stomach and back, and extent or efficiency of object exploration
- controls for many things
What causes the relationship between motor and cognitive development?
giving babies motor experiences facilitates learning
e.g. giving pre-reaching babies reaching practice with sticky mittens for 10 mins/day for 2 weeks
Outcomes of sticky mittens study
evidence for the importance of motor experiences in cognitive development
- more looking, mouthing, reaching
- alternation between oral and visual exploration
- ability to recognize objects from different viewpoints
Developmental cascade
a unique longitudinal relation among interpersonal characteristics
skill (or lack thereof) in one area can come to affect other areas
Developmental cascade in motor skills
motor competence facilitates social learning in other domains and introduces new ways to experience the environment
- being told “no” when crawling or walking leads to increased negative emotionality
- walking allows carrying objects to others to engage with and speak about
- walking infants have better joint attention and language
