why is human motor development so physically slow?
- As human evolved, cortex got bigger (greater cognitive abilities)
- Pelvis got smaller —> walking upright
- Baby’s head will literally not 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
- Humans offset development to experience-expectant plasticity
why is human motor development so culturally slow?
- VAST amounts of input go into making an adult human
- Coming underdeveloped means that subsequent development can be shaped by input to work best with environment you have
- Development optimized based on experience-dependent plasticity
physical growth in babies
- growth is NOT continuous
- Babies may not grow at all for days or weeks and then grown more than a cm overnight
- Nutrition (lack of malnutrition) critical for physical and cognitive growth
- Epigenetic effects of malnutrition during pregnancy
pros of breast feeding
you should breastfeed exclusively until 6 months
- Chest and ear infection, colds, obesity, asthma all reduced in breastfed infants
- Bonding experience
normal baby reflexes
- Patellar reflex (kicking of foot when knew is stimulated)
- Babinsky reflex
- if you touch the bottom of their toes, they’ll expand and contract their toes
- Rooting reflex
- if you touch the side of a newborns face, they’ll turn their head and open their mouth
- Sucking reflex
- Grasping reflex
- same as babinsky but in hand
strange baby reflexes
- Stepping reflex
- they’ll march when held up onto flat surface
- Diving reflex
- they’ll hold their breath if tossed in water
- Tonic neck reflex
- Grasping reflex
- Moro reflex
- when you feel you’re falling in bed and you reach out
why do baby have innate reflexes?
- Valuable to newborns themselves
- Crawling, rooting, sucking, swallowing —> food!
- Building blocks of later development
- Stepping, grasping, crawling
- Useless vestiges from primate ancestors?
- Absence or persistence can indicate developmental disorders
why do reflexes disappear after few months?
- Possibility 1:
- Reflexes reflect newborn infants’ immaturity; reliance on low-level brain systems
- Get replaced by high-level, cortically controlled abilities
- 2-systems view: at first you have a low level system, later you have a higher order system, and in the troph is where they compete and nothing happens
- Possibility 2:
- Reflexes remain, only seem to disappear
Dynamic systems theory (esther helen)
- Motor development not simply mutation of a single high level system, or of several high level system for walking, r teaching, etc.
- Any successful act requires interaction of many things coming together int eh right way
- Developmental changes may reflect change in any component
- Regressions as well as progressions
crawling
- babies differ in their preferred navigation techniques
- some never crawl at all (back sleeping)
- skill improves with tons of practice
reaching
- 4-6 months
- babies reach earlier when posture supported
- over time, they’ll adjust hand-shape for different-sized objects
reach adjustments
- 10 mo reach faster for an object to throw than for an object to be used precisely
- 14 mo + have trouble with reach inversion/ hand switching
tool use
- starts to develop around 9 mo, takes time to plan reaching action appropriately/flexibly
what kind of experience matters?
- must be active (not passive)
- no critical period for experience
- e.g., 6 week crawlers avoid the cliff, but 2 week crawlers cross
north america vs. kenya beliefs on motor development
NA: tend to think motor development progresses largely on its own/ happens when it happens
Kenya: if you don’t teach your children to walk, they won’t walk
effects of cradling
- much motor delay, no LONG term effects
how are motor and cognitive development skills related?
- babies with better motor skills do better at some cognitive tasks, like determining what sounds are made by which objects, perceiving objects as 3D
- relationship between motor and cognitive development persists long term
- those with more motor maturity at 5 months have greater academic achievement at age 14 years
developmental cascades
a unique longitudinal relation among interpersonal characteristics
- skill (or lack thereof) in one area can come to affect other areas
- motor competences introduces new ways of exploring and experiencing the social environment, too
- crawling/ walking= being told no!: exposure to increased negative emotionality
- walking infants have better joint attention (following parents’ gaze, pointing) and better language
