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PSYB20 All Lecture Notes for Midterm 2.docx

Course Code
Mark Schmuckler
Study Guide

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Motor Development
I. Age norms for important motor milestones
II. The development of reaching
A. Underlying skills of visually-guided reaching
1. Perceptual abilities
2. Motor skill
3. Perceptual-motor coordination
B. Reaching in neonates
C. Normative sequence of reaching
D. Reaching for a moving object
E. Reaching with the hands and feet
F. Is visually-guided reaching a myth?
III. The development of locomotion
A. Perceptual information in locomotion
1. Perceiving the properties of surfaces
2. Control of balance
3. Visually-guided locomotion
B. A systems approach to development of walking
1. Component skills
2. Relation between skills
Age Norms For Important Motor Milestones
.typically at the end of first month begin achieving
.variation of these milestones are unrelated to the subsequent growth of emotional/intellectual
.table is avrg age inmonths, motor development continues on into adulthood
Skill 50% 90%
1. Lifts head 90° 2.2 3.2
2. (when lying on stomach )
3. Rolls over 2.8 4.7
4. Sits (propped up) 2.9 4.2
5. Sits (no support) 5.5 7.8
6. Stands holding on 5.8 10.0 (½ yr)
7. Walks holding on 9.2 12.7 (1yr)
8. Stands alone 11.5 13.9 (1yr)

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9. Walks well 12.1 14.3(1 ½ yr)
10. Walks up steps 17.0 22.0 (2 yr)
11. Kicks ball forward 20.0 24.0 (2yr)
Necessary Skills for Visually-Guided Reaching
1. Perceptual skills
Object recognition
Figure-ground separation (distinguish from background;reaching)
Motor skills
Arm and hand coordination(w/o vision yet grasping movement)
Fine-motor coordination and control
2. 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(begin to orient their body)
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 Object(infants are more likely to reach for the obj. as they age
towards the slower object)
Von Hofsten & Lindhagen (1979)
The number of reaches at each speed and age, expressed as a proportion of the maximum
number of possible reaches (3 per condition).

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(18-21 weeks grasping is outperforming touching)
(data shows when infant successfully reach for a moving/stationary obj is the same
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)
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: (infants better control the legs(feet) than the
hands(arms) partly cause of physiology of the infant)
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)
Reaching in the light versus the dark individual subjects
(effect of age, contact and grasp of the obj)
(touch/grasp in the light is the top bars and the below bars are in the dark)
(the bars are the same amount, which tells us that vision-guided reaching is a myth)
(the use of vision maybe for other roles)
Infants’ Perceptions of the Traversability of Surfaces
The Walkway Apparatus (schmuickler)
(walking influence cognition,emotion,attatchment and has a motor component)
(infants actually crawl backwards first, than forwards)
(infants have to know the surface for locomotion,friction)
(style of surface effects locomotion)
(a walking infant can differentiate the surface while moving)
(walking infant no latency while crawling on surface, and showed less displacement behavr;rec)
(real diff was in the waterbed surface where crwling infant showed no diff, but only more explanation
behavr, no displacement behavr;no distinction w/ surface)
(walking infant increased in displacement behavr,distinction with the surfaces)
(Infants chooses rigid surface instead of the waterbed;which suggests the style of locomotion and deals
with the surface of it)
The Visual Control of Posture
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