KNSS 307 Developmentof manipulate skills
what makes humans unique in performing manipuative?
opposable thumbs and being bipedal
Grasping
Prehension is the grasping of an object.
Halverson proposed 10 phases of development in
1931.
Transition from power to precision grips
Imposition of one task, one set of environmental conditions
Hohlstein (1982): Object size and shape influence
type of grasp (by 9 months, infants shape hand to
match object as they reach).
Body Scaling in grasping
Grip movements are body-scaled. (Newell, Scully,
Tenenbaum, & Hardiman, 1989)
Key is hand size relative to object size.
More research is needed in infancy.
Ratio of hand size to object size is consistent for
transitioning from using one hand to using two hands
to pick up object.
learning to reach
- Infants are good at reaching in the dark, so matching vision of the hand and arm with feel of the movement is likely not part of their learning.
-Infants are more likely to learn to control their arms by doing (i.e., repeated reaching for objects).
- Infants align their gaze to where they reach, so they map vision onto their arm movements.
Hand mouth movement
- At 3 to 4 months, infants become consistent in moving the hand to the mouth.
- By 5 months, they open the mouth in anticipation of the hand’s arrival.
bimanual reaching and manipulation
~2 months – infants show bilateral arm extension and reaching
~4-5 months – infants reach for objects with both arms (usually one hand reaches/grabs first)
~12 months – pulling apart and insertion actions (infants will alternate between unimanual and
bimanual reaching throughout year one)
~18 months – manipulate objects cooperatively with both hands
~ 2 years – infants use objects as tools
~2-3 years – complementary activities are observed
role of posture
- Reaching improves when infants can maintain postural control.
- By 4 months, infants can adjust their posture as they reach.
- What postural constraints could serve as limiters to the rate of development of reaching?
Manual Performance in Adulthood
Kauranen & Vanharanta (1996)
Manual performance declined after age 50.
Movements slowed; coordination scores declined.
Hughes et al. (1997)
Strength declined.
More individuals exceeded time thresholds.
Some loss in coordination of handwriting
Accuracy maintained, especially in well-practiced
tasks
Catching Anticipation
- Anticipation is involved in many manipulative tasks and interception skills.
- Studies often involve coincidence-anticipation tasks (anticipating completion of movement to coincide with arrival of moving object).
development of coincidenc-anticipation
- Interception success is often related to ball size, speed, trajectory, and other task and environmental constraints.
- Performance is well developed by the teens.
- Why might studies on coincidence-anticipation reflect
limits of perception more than real-world catching skill?
how do cjildren learn to arrive at the righ place?
- Perhaps children learn that the ratio is zero when they stand still and catch a ball.
- Eventually they learn to move to keep the ratio at zero.
- Experience is important in learning to move to catch.
- Parents, teachers, and coaches can manipulate information constraints during exploratory
practice.
- Identifying important sources of information might also help novice adults.
Catcjing older in Adulthood
- Little research is available.
- Catching might be influenced by factors affecting movement speed or ability to reach.
- Older adults are somewhat less accurate and more variable on coincidence-anticipation tasks.
- Older adults can improve with practice.