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Motor Development. Age norms for important motor milestones The development of reaching Underlying skills of visually-guided reaching Perceptual abilities Motor skill Perceptual-motor coordination Reaching in neonates Normative sequence of reaching Reaching for a moving object
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Motor Development • Age norms for important motor milestones • The development of reaching • Underlying skills of visually-guided reaching • Perceptual abilities • Motor skill • Perceptual-motor coordination • Reaching in neonates • Normative sequence of reaching • Reaching for a moving object • Reaching with the hands and feet • Is visually-guided reaching a myth? • The development of locomotion • Perceptual information in locomotion • Perceiving the properties of surfaces • Control of balance • Visually-guided locomotion • A systems approach to development of walking • Component skills • Relation between skills
Age Norms For Important Motor Milestones Skill50%90% Lifts head 90° 2.23.2 when lying on stomach Rolls over2.84.7 Sits (propped up)2.94.2 Sits (no support)5.57.8 Stands holding on5.8 10.0 Walks holding on9.212.7 Stands alone 11.5 13.9 Walks well12.114.3 Walks up steps17.0 22.0 Kicks ball forward20.0 24.0
Necessary Skills for Visually-Guided Reaching • Perceptual skills • Object recognition • Figure-ground separation • Motor skills • Arm and hand coordination • Fine-motor coordination and control • Visual-motor integration and coordination • Visual guidance of the hand • Timing of the grasp
The Normative Sequence of Reaching • 1 – 2 Months • Glance at objects when present • Begin to fixate objects for 5-10 sec • Arms not organized with vision • 2 – 3 Months • Isolation of components breaks down • Focus on objects • Beginning of prehensory behavior • Raise hand towards object • 3 – 4 Months • Mutual grasping, 1 or 2 hands • Sometimes turn torso towards object • 4 – 5 Months • Integrated looking and grasping • “Top-level” reaching • Good grasping of object
Type of Contact With a Moving ObjectVon Hofsten & Lindhagen (1979) Claus von Hofsten The number of reaches at each speed and age, expressed as a proportion of the maximum number of possible reaches (3 per condition).
Type of Contact With a Moving ObjectVon Hofsten & Lindhagen (1979) Claus von Hofsten The type of contact with the object. Proportion of total number of reaches for “grasp,” “touch,” and “miss.”
Reaching with the hands vs. feet (Galloway & Thelen, 2004) • Esther Thelen • Compared timing for reaching with the hands versus reaching with the feet • Tested 8-15 week olds longitudinally (weekly) • Presented toy at midline between shoulders, and midline of hips • Timing of reaching with hands and feet: • Average age of first contact: Hands: 15.7 weeks; Feet: 11.7 weeks • Extended contact with object: Hands: 16, Feet: 11.8
Is Visually-Guided Reaching a Myth Clifton, Muir, Ashmead, & Clarkson (1993) Rachel Keen Darwin Muir Reaching in the light versus the dark – individual subjects
Infants’ Perceptions of the Traversability of Surfaces Eleanor J. Gibson (Gibson, Riccio, Stoffregen, Schmuckler, Rosenberg, & Taormina,1987) The Walkway Apparatus
The Visual Control of Posture(Lisman & Lee, 1983) David Lee Thomas Stoffregen (Stoffregen, Schmuckler, & Gibson,1987) The Moving Room Apparatus
