- Humans are extraordinarily adaptable
Learning to move: the typical sequence
- Dramatic changes in posture
- Baby just sits there
o It then can start crawling around
o 5% of babies just go from sitting to walking
o This is not an absolute sequence that each stage must be visited
- How do infants learn to walk?
- Pinker says
o The way one walks is demanding and a recipe for disaster
o As we are walking, we are constantly throwing ourselves forwards and catches ourselves
back onto our two feet
- Walking requires sophisticated internal “control” program
o How does the program develop?
What goes on during Walking
- Highly coordinated series of alls
- Coordination of 200 skeletal muscles
- Back muscles prevent forward fall
- Abdominal muscles prevent backward fall
- 30 muscles to move one leg and move forward
Center of gravity goes up and down, and left and right
- Each leg alternates between taking full weight of body and moving freely
- Each hip sways backwards and forwards
o As change support leg, sway left and right
Our gait adapts rapidly to new situations
- We are able to use perceptual information to adapt our gait on-line
- As we walk, we must adapt to the changes in the environment
What happens during walking: Summary
- Multiple parts moving in sync
o Multiple limbs (eg. Arms & legs) o Joints & muscles within same limb (eg. 30 muscles in leg)
- Maintain balance while body changes constantly
o Supporting leg alternates between left and right
o Centre of gravity goes up and down and left and right
o Hips sway backwards and forwards
- Make on-line adjustments based on perceptual information
o Ice, sand, narrow surface, etc…
Why there must be a program that controls walking
- The program or “conductor”
o Coordinates all the parts in motion
o Keeps them balanced
o Continuously adjusts their motion and balance according to information about surfaces
(ice, sand, concrete, etc.) and changes in body shape (eg. Carrying boxes) coming from
- How does it develop?
o How do we acquire the ability to adapt to new situations?
To be able to walk, must wait until shape of body changes
- Newborns and young infants are “top heavy”
o Relative to size of their body, have very big heads
- If tried to walk, would always fall down because of that
o Think of how easy it would be to tip over tree with no roots. Baby is the same.
- There is a change in head size to body size ratio
o Difficult to stand up when young
How walking develops: Dynamic systems theory
- Walking demands orchestration of many skills
o Moving limbs to particular positions
o Maintaining balance
o Integrating perceptual information, etc.
- According to dynamic systems, each skill first redefined on its own, then, once each skill is
mastered, babies learn to coordinate them
- Do infants really need experience to develop each skill? A few test cases.
o Coordinating legs during walking
o Using information from senses to maintain balance
- Skills to develop so that you will not look silly when walking
Stepping: Must babies learn to alternating motion of legs required for walking? - Test: put 6 and 7 month olds who have never walked on a treadmill (babies generally start
walking when 12 months old)
o Will they just let their legs be dragged backwards?
o Or will they walk?
They simply walk like an adult
Shouldn’t be something that babies could imitate walking (visual
- If place each leg on separate treadmill moving at different speed, 6 and 7 month olds adapt leg
o One leg moves faster than other!
- Must use information about position of body in space
- Two main sources
o “Inner eye”: we can feel our body moving in space even with our eyes closed
Involves perceptual mechanism in inner ear
Semicircular canals: tiny tubes filled with fluid. When we move, fluid moves, and