Motor Development n Newborn- not much activity (except when crying) n Reflexes begin to fade- voluntary comes on –(2-4 months)- big increase in activity n Early movements –Tentative –Jerky- not smooth; clumsy –Uncoordinated –Why?
Motor Development n Motor control progresses with neural development –Myelination of the neurons in the cerebellum occurs with this increase in activity n Cephalocaudal/proximal-distal –Downward and outward n Control of Head, trunk, arms, legs n Head & trunk before arms and legs –Arms & legs before hands and feet –Hands and feet before fingers and toes n In spite of the fact that there is almost no difference in physical development, boys are more advanced over girls in abilities that emphasize force and power. Why?
Age Norms Task50%90% Lifts head2.23.2 months Sits with support5.57.8 Independently sits6.5 9.0 Crawls7.09.0 Stands alone11.513.9 Walking12.114.3 Stairs17.022.0 Jumping23.530.0 Running (early)2.5 yrs3.0 years These have been changed to 9.0 and 10.5 due to SIDS intervention which decreases experience with movement on stomach Why/how do we develop motor skills? Why do we walk? Nature or nurture?
Theories of Motor Development n Maturational (nature) –Motor development is a genetically programmed sequence n muscles & nerves mature –Downward & outward n Sufficient for development –Maturation is all that’s needed for motor skills to develop n Twin Studies (Gessell & Thompson, 1929)- Maturation is what is important –One twin gets practice (walking, stairs) –Co-twin restricted activity/no practice –No difference in age of acquisition (first steps)
Theories of Motor Development n Experiential (nurture) –Motor development requires opportunities to learn n maturation required, but not enough –need chance to learn from experience n practice facilitates development or improves motor skills n institutionalized infants (Dennis, 1960) –Infants in orphanage (Iran) –Not placed in sitting position –Fed with propped bottle –No interaction –Spent 1st two years in crib –18-24 m, none could walk –½ were able to sit alone –3-4 years, only 15% walking –However, these are all “failure to thrive” infants. Many other variables that could be playing a role. –Take home message: practice doesn’t speed up maturation, but experience is necessary for motor skills to develop
Theories of Motor Development –Dynamic Systems (Esther Thelan) n Incorporates both maturation and learning as equally important n Maturation, experience, perceptual skills (systems) interact n Changes involving growth and skill acquisition in one area or system will impact performance n Motor skills are constructs (Thelan)- Emerges as infant actively reorganizes existing motor skills into new and more complex actions –Early constructs- tentative, uncoordinated –Toddler- spends lots of time on behind
Dynamic Systems cont. n Multiple factors influence development –Biological n Development of sensory system n CNS, Skeletal & muscular systems develop creating muscle tone and strength –Social n Mother-infant dyad n Stimulating environment? Reinforcing? Encouraging n Facilitating development of skills with experience –Experiential n Floor time increases development of trunk control
Dynamic Systems cont. n Infants are goal directed –Why work so hard? Why do we walk? –Eager to acquire new skills that will help n Get interesting new objects n Facilitate social/comfort contact –Humans are curious
Dynamic Systems cont. n Example: Crawling- any delay in any of these steps delays crawling. –Infants develop 3 skills independently n Lift & turn head n Hand preference in reaching n Kicking legs –This turns into: n Raise head & turn it towards sight/sound n Reach with preferred hand for object n Kick with leg opposite of outstretched hand –Infant reorganizes these into crawling n Visual orientation n Reach orients body in right direction n Kicking propels body forward
Developmental Milestones Directions: Below is a list of gross and fine motor milestones that develop during the first two years. Place them in the order in which they typically occur (that is, average age achieved). Milestones: 1. rolls from side to back 2. plays pat-a-cake 3. grasps a cube 4. when held upright, holds head erect and steady 5. jumps in place 6. pulls to a stand 7. walks alone 8. rolls from back to side 9. scribbles vigorously 10. stands alone 11. walks on tiptoe 12. walks up stairs with help 13. sits alone 1. 4 2. 1 3. 3 4. 8 5. 13 6. 6 7. 2 8. 10 9. 7 10. 9 11. 12 12. 5 13. 11