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