Development of Manipulative Skills chapter 8 Development of Manipulative Skills Click to add notes

Manipulative Skills and the Model of Constraints Individual structural constraints are involved, and these change with age. Environmental and task constraints are also involved.

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

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.

Halverson’s Phases of Grasping Development See figure 8.1 on page 137 in the textbook. Click to add notes

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.

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.

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)

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.

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.

Visually Elicited Reaching Dominant by age 12 months A more thrusting, ballistic movement Accurate; few corrections needed

Hand–Mouth 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 hand’s arrival.

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)

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.

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.

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

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.

Fundamental Manipulative Skills Performer gains possession or control of an object. Catching is the most common.

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.

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

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)

Proficient Catching (continued)

Developmental Changes in Catching Task constraints greatly affect the difficulty of catching. Arm action Little response Hugging Scooping Arms “give” (continued) Click to add notes

Developmental Changes in Catching (continued) Hand action Palms up Palms in Palms adjusted Body action No adjustment Awkward adjustment Proper adjustment

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.

Development of Coincidence Anticipation Children’s 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.

Perception–Action Perspective Two important characteristics of the person–environment 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)

Perception–Action 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.

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.

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.

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.

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.

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.