Development of Manipulative Skills

1
chapter 8

• Development of Manipulative Skills

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Manipulative Skills and the Model of Constraints

• Individual structural constraints are involved,
  and these change with age.
• Environmental and task constraints are also
  involved.

3
Reaching and Grasping

• The proficient execute the reach and the grasp as
  a single skill.
• Study here is of grasping first, then reaching.

4
Grasping

• Prehension is the grasping of an object, usually
  with the hand or hands.
• Halverson proposed 10 phases of development in
  1931.
• Transition from power to precision grips
• One task and one set of environmental conditions
  imposed
• Hohlstein (1982) demonstrated that shape and size
  of an object influence the specific type of grasp.

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Halversons Phases of Grasping Development

• See figure 8.1 on page 137 in the textbook.

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More on Grasping

• Vision is important for grasping.
• Adults use visual information to configure the
  hand before the grasp.
• Children might be more dependent on visual
  feedback to configure the hand than adults are.
• Grasping is stable over the life span.
• Disabling conditions, such as arthritis, can
  influence configuration.

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Body Scaling in Grasping

• Newell, Scully, Tenenbaum, Hardiman (1989)
  suggested grip movements are body scaled.
• Hand size relative to object size is key.
• More research is needed in infancy.
• Research on children and adults demonstrates that
  the ratio of hand size to object is consistent
  for transitioning between using one hand to two
  hands to pick up an object.

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Reaching

• Many researchers propose that infants demonstrate
  prereaching.
• Prereaching is an extension movement elicited by
  an object, not necessarily resulting in contact.
• Moving objects in particular elicit prereaching.
• (continued)

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Reaching (continued)

• Facilitative postures might be required for
  prereaching.
• Prereaching does not involve configuration of the
  hands, and newborns do not use visual feedback to
  guide prereaches.

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Visually Guided Reaching

• It predominates between 4 and 7 months.
• Corrections are made during reach based on vision
  of object and hand.
• Evidence has been obtained by observing reaches
  with prisms that displace the apparent position
  of the object and hand.

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Visually Elicited Reaching

• Dominant by age 12 months
• A more thrusting, ballistic movement
• Accurate few corrections needed

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HandMouth Movements

• 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 hands arrival.

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Bimanual Reaching and Manipulation

• At 2 months, infants show bilateral arm extension
  and reaching.
• Around 4.5 months, infants reach for objects with
  both arms.
• Usually one hand reaches and grasps object first.
• For a time, bimanual reaching actually declines.
• At 7 months, infants show evidence of reaching
  with one arm or two as appropriate for the
  object.
• (continued)

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Bimanual Reaching and Manipulation (continued)

• By 12 months, pulling apart and insertion actions
  are seen.
• After 18 months, infants manipulate objects
  cooperatively with both hands.
• By the end of the second year, complementary
  activities are seen.

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Role of Posture

• We adjust posture to reach.
• Before infants can sit, they must be supported in
  order to reach.
• Reaching improves when infants can maintain
  postural control.

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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

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Rapid Aiming Movements

• These movements have an initiation and
  acceleration phase to peak velocity, then a
  deceleration and termination phase.
• Young adults tend to make symmetrical movements,
  whereas older adults have a longer deceleration
  phase in order to make adjustments in the final
  phase.

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Fundamental Manipulative Skills

• Performer gains possession or control of an
  object.
• Catching is the most common.

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Catching

• Ideally, objects are caught in the hands so they
  can be manipulated.
• Children initially position the arms and hands
  rigidly and sometimes trap the ball against their
  chests.
• Children sometimes turn their heads away or close
  their eyes.

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Beginning Catching
Drawn from film tracings available from the
Motor Development Film Collection, Bowling Green
State University
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Proficient Catching

• Hands give with the ball to gradually absorb
  force.
• Catcher moves side to side or forward and back to
  intercept the ball.
• Fingers are pointed up for high balls and down
  for low balls.
• (continued)

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Proficient Catching (continued)
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Developmental Changes in Catching

• Task constraints greatly affect the difficulty of
  catching.
• Arm action
• Little response
• Hugging
• Scooping
• Arms give
• (continued)

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Developmental Changes in Catching (continued)

• Hand action
• Palms up
• Palms in
• Palms adjusted
• Body action
• No adjustment
• Awkward adjustment
• Proper adjustment

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Anticipation

• Many manipulative tasks and interception skills
  involve anticipation.
• Anticipatory aspects of skills are often studied
  with coincidence-anticipation tasks in which one
  anticipates the completion of a movement to
  coincide with the arrival of a moving object.

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Development of Coincidence Anticipation

• Childrens accuracy is not as good if the
  response is complex or the interception point is
  farther away.
• Young children are more successful with large
  balls and flatter trajectories.
• Ball colors and backgrounds have less effect with
  advancing age.
• Speed influences accuracy, but the pattern is
  complex.

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PerceptionAction Perspective

• Two important characteristics of the
  personenvironment system for catching involve
  constant patterns of change.
• Invariants stable patterns
• Expanding optical array visual pattern that
  expands or constricts on the retina
• Invariance in moving sideways was investigated
  through the constant bearing angle strategy.
• (continued)

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PerceptionAction Perspective (continued)

• McLeod and Dienes (1993, 1996) investigated
  whether catchers intercept a moving ball by
  keeping a ratio, based on an angle of gaze, at or
  near zero.
• Oudejans et al. (Michaels Oudejans, 1992
  Oudejans et al., 1996) investigated whether
  catchers keep the vertical optical acceleration
  of the ball close to zero.

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How Do Children Arrive at the Right 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.
• Parents, teachers, and coaches can manipulate
  information constraints during exploratory
  practice.
• Identifying important sources of information
  might also help novice adults.

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Catching in Older Adulthood

• Little catching research is available.
• Factors that would affect movement speed or
  ability to reach might affect catching.
• Older adults are somewhat less accurate and more
  variable on coincidence-anticipation tasks.
• Older adults can improve with practice.

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Driving and Piloting

• Older adults have more difficulty dividing
  attention, are slower in moving, and take longer
  to plan movements.
• Expertise on familiar tasks and highly practiced
  skills can be well maintained.
• Driving and piloting are affected by changing
  individual constraints in older adulthood,
  especially under certain environmental and task
  constraints.

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Manipulative Skills Summary

• Manipulative skills set humans apart.
• Infants become skilled at reaching and grasping.
• Children are accomplished catchers by age 11 to
  12 years, but catching tasks requiring movement
  are difficult.
• Aging probably affects getting to a ball more
  than it affects the manipulative aspects of
  catching.

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Assessment of Catching

• For comparisons, task constraints must be
  consistent.
• The number of catches in a set of attempts can be
  scored.
• The developmental sequence can provide
  information about the movement process.