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eywords0 'FF&2('.D$3H D2'@+-./H ($9$+&:;$.)'+ 3)'/$3H F$)'+ ;&)-+-)BH +&D&;&)-&.H ;&6-+-)BH ;&)&2 ;-+$3)&.$3H .'9-/')-&.H :$2D$:)-&.I'D)-&.H :&3)72$H @'+,-./ !"#$%&'(#)%" “Four legs good, two legs better!” (George Orwell, 1996/1946, Animal Farm, p. 132) *'+,-./ -3 3:$D-'+> E. 3D-$.D$H +-)$2')72$H '2)H '.( 2$I +-/-&.H @'+,-./ 7:2-/#) 3$:'2')$3 D#-+( F2&; -.F'.)H ;'. F2&; 6$'3)H F2$$(&; F2&; 3+'9$2BH '.( ;&2'+ 2-/#I )$&73.$33 F2&; )72:-)7($> E) -3 .& 'DD-($.) )#') 3& ;7D# &F &72 ($9$+&:;$.)'+ -D&.&/2':#B ($:-D)3 7:2-/#) +&I D&;&)-&. '3 )#$ $J'+)$( $.(:&-.) &. )#$ 2&'( &F ($9$I +&:;$.)'+ :2&/2$33> !"#$%&' )*+%',-. /010#2*30&-"# 452&6 27 8+2'+066 "#$ F';&73 :-D)72$ &F LThe March of Progress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he March of Progress '.( -.F'.)3R .&2;')-9$ '3D$.) '+&./ )#$ 3)'-2D'3$ &F ;&)&2 ;-+$3)&.$3 37//$3) ' ($)$2;-.-3)-D 3$T7$.D$ )&@'2( -.D2$'3-./+B ;&2$ '(9'.D$( F&2;3> 53 U&7+( NPVWVQ :&-.)3 &7)H )#$ @&2( L$9&+7)-&.M #'3 6$D&;$ ' 3B.&.B; F&2 L:2&/2$33>M =9$. )#$ D#':)$2 )-)+$H L"#$ %&'( )& X&;& 3':-$.3HM -. )#$ "-;$I1-F$ 6&&, NX&@$++H PVYZQ F&2 @#-D# The March of Progress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he March of Progress F&2 $9&,-./ )#$ .&)-&. &F '. $9&+7)-&.'2B +'(($2 @-)# 7:2-/#) ;'. &. )#$ )&: 27./] 2')#$2H #$ '2/7$(H #7;'.3 '2$ ;$2$+B ' 3;'++ )@-/ &. ' 62'.D# &F )#$ $9&+7)-&.'2B 673#> "#$ ($9$+&:;$.)'+ ;-+$3)&.$ D#'2)3 ;-32$:2$3$.) )#$ :2&D$33 &F ($9$+&:;$.) -. )#$ 3';$ @'B )#') The March of Progress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`3BD#&+&/B 8$I :'2);$.)H ?$@ A&2, 4.-9$23-)BH Y *'3#-./)&. `+>H %&&; aPbH ?$@ A&2,H ?A Pbbbc] $I;'-+0 <'2$.>5(&+:#d.B7>$(7> "#-3 @&2, @'3 37::&2)$( 6B ?')-&.'+ E.3)-)7)$ &F [#-+( X$'+)# '.( X7;'. 8$9$+&:;$.) U2'.) %ceIX8ccaWY )& <=5> *$ )#'., C';-2' E2'9'.- '.( 1'.' <'2'3-, F&2 )#$-2 6$'7)-F7+ +-.$ (2'@-./3H '.( f$33$ 1-./$;'. '.( *#-).$B [&+$ F&2 )#$-2 #$+: @-)# F-/72$3> *$ '2$ /2')$F7+ )& ^'2, S+7;6$2/H f&#. O2'.D#',H '.( )& )#$ ;$;6$23 &F <=5R3 /2'(7')$ 3$;-.'2 &. :$2D$:)7'+I;&)&2 ($9$+I &:;$.) @#& /'9$ 73 37D# 73$F7+ D&;;$.)3 &. (2'F)3 &F )#$ ;'.7I 3D2-:)> Adolph, K. E. & Robinson, S. R. (in press). The road to walking: What learning to walk tells us about development. In P. Zelazo (Ed.) Oxford handbook of developmental psychology. NY: Oxford University Press.

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Page 1: The road to walking: What learning to walk tells us about development

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Page 2: The road to walking: What learning to walk tells us about development

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Figure 1. Icons of developmental progress. (A) Rendition of “The March of Progress.” (B) Developmental motor milestone chart. Horizontal bars denote normative ranges for age at onset of each skill. Small vertical lines denote median onset ages.!

Page 3: The road to walking: What learning to walk tells us about development

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Alternating Leg Movements

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Figure 2. Alternating leg movements in infants. (A) Newborn stepping. (B) Supine kicking. (C) Stick diagrams of leg move-ments in upright stepping and supine kicking in a representative 2-week-old infant. The lines chart the movements of one of the infant’s legs at toe, ankle, knee, and hip every 33 ms.!

Page 4: The road to walking: What learning to walk tells us about development

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Figure 3. Relative timing of limb movements in a representative infant crawling on (A) hands and knees and (B) belly. Shaded regions represent time when the limb (or belly) was supporting the body. Open regions represent time when the limb (or belly) was moving forward. Figure 4. Some of the many individual variations in infants’ crawl-

ing patterns. Left column illustrates increasingly erect crawling postures: “army” crawls with the belly continually on the floor, “inchworm” crawls in which infants launch themselves onto their bellies, standard hands-and-knees crawling, and “bear” crawls on hands and feet. Columns represent combinations of arms, legs, and belly used for propulsion and balance. Each row represents a unique crawling pattern displayed by at least one infant.!

Page 7: The road to walking: What learning to walk tells us about development

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Page 8: The road to walking: What learning to walk tells us about development

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Page 9: The road to walking: What learning to walk tells us about development

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1"0/#*

“Q: Dear Mr. Dad: My sister and I have toddler girls who are only a week apart. Hers started walking at about 9 months, but at 16 months mine still hasn't taken a step. Our pediatrician isn't worried and I know I shouldn't compare my baby to anyone else's, but it's hard not to. Is there anything I can do encourage my baby to walk?”

“A: No. On average, babies take their first steps at about 12 months. But, the range is pretty big, from 9 to 18 months. How early—or late—a child starts to walk depends on a number of factors…. Bottom line? Your

baby will learn to walk when she's good and ready and there's nothing you can—or should—do to change her

schedule.” —Armin Brott, “Mr. Dad”

(Brott, 2005, February)

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Page 10: The road to walking: What learning to walk tells us about development

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Figure 5. Van Gogh’s (1890) painting, “First Steps,” illustrating an infant’s first walking steps from one parent’s arms to the other.!

Page 12: The road to walking: What learning to walk tells us about development

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Figure 6. Formal exercise and massage practices used in Africa, India, and the Caribbean that are used to facilitate infants’ motor develop-ment: (A-C) massage and molding of infants’ head, face, and body; (D-F) suspension and shaking by arms, head, and ankles; (G-I) practice of sitting and upright postures.!

Page 13: The road to walking: What learning to walk tells us about development

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Page 14: The road to walking: What learning to walk tells us about development

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One day the father came home to dinner and placed his cuffs upon a table…. The child, seeing the cuffs, crept to the table, pulled herself up by the leg of the table, took the cuffs…and slipped them over her wrists, standing unsupported while doing it…. Then, to the great surprise of the father, she walked with great con-fidence with a pleased expression on her face…. With-out the cuffs, however, she could not be induced to take a single step. She was given an old pair of cuffs and she seemed greatly delighted; she walked and ran as before. She used the cuffs for two days, after which she walked without them and did not revert to crawling.

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Page 15: The road to walking: What learning to walk tells us about development

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Figure 7. Example of footfalls during walking in (A) an infant who had only 2 weeks of walking experience and (B) an infant who had 2 months of walking experience. Each mark reflects the pressure of the infants’ feet as they walked over a mechanized gait carpet. The axes denote the spatial coordinates of each footfall.!

Page 16: The road to walking: What learning to walk tells us about development

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Figure 8. The characteristic time course of improvement in several measures of children’s walking gait over the first 60 months of independent walking. Step length = distance between consecutive steps. Step width = lateral distance between steps. Foot rotation = absolute value of in/out-toeing from path of progression. Velocity = overall distance/time. Swing time = amount of time with one foot moving through the air. Double support = amount of time that both feet are on the floor. Ver-tical acceleration of the center of gravity = rate of change in velocity of the center of gravity along the vertical axis.

Page 17: The road to walking: What learning to walk tells us about development

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Figure 9. Paradigms for testing infants’ perception of affordances as they encounter variable and novel challenges to balance and locomo-tion: (A) approaching an apparent drop-off on a visual cliff; (B) approaching an actual drop-off on a real cliff or (C) adjustable gap in the surface of support; (D) descending an adjustable slope; (E) crossing bridges of various widths and heights; (F) using wobbly or rigid han-drails to augment balance on narrow bridges. An experimenter (shown) followed alongside infants to ensure their safety. Caregivers (shown only in Figure 9A and Figure 9B) encouraged infants from the far side of the obstacle.!

Page 19: The road to walking: What learning to walk tells us about development

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Figure 10. Gait modifications in an exemplar infant walking down slopes. (A) Scatter plot showing a positive correlation between step number on the slope and the degree of slope an-gle. A larger number of steps signify a smaller average step length. Each symbol represents the result of one trial. (B) Foot-prints as the infant walked down a challenging 24° slope. The image represents an overhead view of the sloping walkway. Solid vertical lines demarcate portions of the walkway. The leftmost portion represents the flat starting platform. The mid-dle section represents the slope. The rightmost portion represents the flat landing platform. Therefore, the direction of the infant’s walking progressed from left to right. Each symbol represents one step. The tiny steps on the sloping portion of the walkway are summarized by one data point in the scatter plot in Figure 10A. The cluster of tiny steps on the flat starting plat-form at the brink of the slope indicates that gait modifications were planned prospectively.!

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Figure 11. Variety of means for (A) descending slopes and (B) using wobbly handrails to augment balance on narrow bridges.

Page 21: The road to walking: What learning to walk tells us about development

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Page 23: The road to walking: What learning to walk tells us about development

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Page 24: The road to walking: What learning to walk tells us about development

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Figure 12. Metaphors of development. (A) Waddington’s (1957) epigenetic landscape. (B) Banyan tree with diverging and merging roots and branches.

Page 25: The road to walking: What learning to walk tells us about development

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Page 26: The road to walking: What learning to walk tells us about development

58G1`X!5?8!%GSE?CG?!gY

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Page 27: The road to walking: What learning to walk tells us about development

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Other Roads

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Figure 13. African women and Nepalese porters carrying heavy head loads in (A) an upright position and (B) supported by a strap across the forehead.

Page 28: The road to walking: What learning to walk tells us about development

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Page 29: The road to walking: What learning to walk tells us about development

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The Road Behind

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The Road Ahead

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The Road Less Traveled

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Page 30: The road to walking: What learning to walk tells us about development

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Page 32: The road to walking: What learning to walk tells us about development

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Page 33: The road to walking: What learning to walk tells us about development

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Page 34: The road to walking: What learning to walk tells us about development

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Page 35: The road to walking: What learning to walk tells us about development

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E.!1>!['2;-D#'$+!N=(>QH!Manual of Child Psychology!N::>!gVZIccPQ>!?$@!A&2,0!f&#.!*-+$B>!

U$3$++H!5>H!j!52;')27('H![>!C>!NPVaPQ>!Developmental diagnosis: Normal and abnormal child development>!?$@!A&2,0!X'2:$2!j!%&@>!

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Page 38: The road to walking: What learning to walk tells us about development

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Page 39: The road to walking: What learning to walk tells us about development

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Page 40: The road to walking: What learning to walk tells us about development

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Page 41: The road to walking: What learning to walk tells us about development

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Page 42: The road to walking: What learning to walk tells us about development

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