Motor Development

I. Age norms for important motor milestones

II. The development of reachingA. Underlying skills of visually-guided

reaching1. Perceptual abilities2. Motor skill3. Perceptual-motor coordination

B. Reaching in neonatesC. Normative sequence of reachingD. Reaching for a moving objectE. Is visually-guided reaching a myth?

III. The development of locomotionA. Perceptual information in locomotion

1. Perceiving the properties of surfaces2. Control of balance3. Visually-guided locomotion

B. A systems approach to development of walking1. Component skills2. Relation between skills

Age Norms For Important Motor Milestones

Skill 50%90%

 Lifts head 90° 2.2

3.2 when lying on stomach

Rolls over 2.8 4.7 Sits (propped up) 2.9

4.2 Sits (no support) 5.5

7.8 Stands holding on 5.8 10.0 Walks holding on 9.2

12.7 Stands alone 11.5

13.9 Walks well 12.1 14.3 Walks up steps 17.0

22.0 Kicks ball forward 20.0 24.0

Necessary Skills for Visually-Guided Reaching

1. Perceptual skills• Object recognition• Figure-ground separation

2. Motor skills• Arm and hand coordination• Fine-motor coordination and control

3. 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

Reaching For A Moving Object

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 Object

The type of contact with the object. Proportion of total number of reaches for “grasp,” “touch,” and “miss.”

Is Visually-Guided Reaching a Myth

Reaching in the light versus the dark – individual subjects

Infants’ Perceptions of the Traversability of Surfaces

The Walkway Apparatus

The Visual Control of Posture

The Moving Room Apparatus

Visually-Guided Locomotion in Toddlers

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5 0 .0

1 0 0 .0

Per

cent

Suc

cess

12-month-o lds

18-month-o lds

24-month-o lds

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5 0 .0

1 0 0 .0

Per

cent

Fai

lure

0 2 4 6 8 1 0 1 2

B arrie r H e ig h t ( in ch es)

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1 0 0 .0

Per

cent

Ref

usal

Visually-Guided Locomotion in Toddlers

-6 -4 -2 0 2 4 6

B arrie r H e ig h t(re la tiv e to th re sh o ld )

0.2

0.4

0.6

0.8

1.0

Go-

rati

o ((

S+

F)/

(S+

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R))

12-month-o lds

18-month-o lds

24-month-o lds

A Systems Approach to Locomotion