Motor Development

Gross Motor Milestones

Major Milestones by Age

  • Newborn:

    • Moro, positive support primitive reflexes; flexed posture.

  • 2 months:

    • Head up 45° in prone position.

  • 4 months:

    • Asymmetrical tonic neck reflex; lifts chest in prone.

  • 6 months:

    • Primitive reflexes gone; pulls to sit; sits tripod.

  • 9 months:

    • Postural reflexes present; rolls both ways; sits well.

  • 12 months:

    • Gets to sit; crawls; pulls to stand; walks with one hand help; catches a rolling ball.

  • 18 months:

    • Stands and walks alone; walks up and down stairs with railing.

  • 24 months:

    • Runs, jumps, kicks; throws ball overhand three feet; walks up stairs marking time, no railing.

  • 36 months:

    • Pedals tricycle; walks down stairs marking time; walks up stairs alternating feet.

  • 48 months:

    • Hops; walks backward in line.

  • 60 months:

    • Catches ball; balances on one foot; performs sit-ups; skips.

  • Reference: Dosman et al. (2012)

Reflexes

Definition

  • Involuntary, rapid movements in response to stimuli; aids in danger avoidance.

Common Reflexes

  • Withdrawal Reflex: Protects from harmful stimuli.

  • Blinking Reflex: Protects eyes from sudden irritants.

  • Coughing Reflex: Clears airway.

  • Infant Reflexes:

    • Stepping Reflex: Early kicking motion, precursor to walking?

    • Asymmetric Tonic Reflex: Head turn leads to stance resembling fencers.

    • Grasping Reflex: Response to palm stroke.

    • Moro Reflex: Startle response to loud sounds.

    • Rooting Reflex: Stimuli at cheek for feeding orientation.

    • Babinski Reflex: Response to stroke on the sole of the foot.

Primitive Reflexes

  • Controlled by medulla and midbrain; indicate neurological health potentially.

  • Disappearance by 6-8 months is normal; persistence may indicate issues.

Adaptive Reflexes

Characteristics

  • Disappear during the first year; assist survival mechanisms.

  • Examples include sucking, swallowing, rooting reflexes.

  • Weak or absent reflexes could indicate neuronal developmental concerns.

Body Growth

Growth Patterns

  • A child's body grows faster in the first two years than at any time later.

Growth Chart

  • Age | Average Height | Average Weight

    • Newborn: 20 inches, 7.5 pounds

    • End of Year 1: 32 inches, 22 pounds

    • End of Year 2: 36 inches, 30 pounds.

  • Cephalo-caudal pattern: Growth proceeds from head to tail; head at birth accounts for ¼ total length.

  • Proximo-distal pattern: Growth proceeds from center to periphery; trunk develops before limbs.

  • Reference: Berk (2019)

Maturation Theory

Overview

  • Follows a cephalo-caudal pattern indicating sequence of events in motor skill acquisition (e.g., head control, reaching).

  • Quote: "Development is controlled by a maturational timetable; each species has its sequence and experience has little effect on motor development." (Slater & Bremner, pp. 47)

Milestones in Posture and Locomotion

Acquisition of Sitting

  • Newborn: complete head lag; 3 months: slight head lag; 6-7 months: sits without support.

  • 12 months+: sits in a chair.

Ventral Suspension

  • Newborn: lack of head control.

  • 8 weeks: maintains head in line.

  • 5-6 months: keeps chest and shoulders off surface during weight-bearing.

Prone Positioning and Crawling

  • By 3 months: can roll from prone to supine; by 8 months: crawling requires muscle control.

Standing and Walking Progression

  • 2 months: momentary head control; 6 months: bears weight, 9 months: pulls self up to standing; 15 months: stands without help.

Sources of Variability in Motor Development

Factors Influencing Development

  • Intrinsic Variables: Physical characteristics and temperament.

  • Extrinsic Variables: Environment, socioeconomic status, family, culture.

Questioning Maturation Theory

  • While maturation theory describes broad trends, the sequence of motor development is not entirely genetically predetermined.

Fine Motor Skills

Overview

  • Involve precise movements of the hand and fingers; include pincer grasp and eye-hand coordination.

  • Linked with visuo-spatial skills, involving both motor and cognitive abilities (Gerber et al., 2010).

Fine Motor Milestones by Age

  • Newborn: Rooting, sucking, orients to sound.

  • 2 months: Gurgles; 4 months: Coos; 6 months: laughs.

  • By 18 months: self-feeds using fingers; by 24 months: copies vertical line; 36 months uses spoon and fork.

  • By 60 months: proficient in drawing and copying shapes.

  • Reference: Dosman et al. (2012)

Developmental Rhythms in Grasping and Reaching

Grasping Skills

  • Reflexive grasp at newborn stage; develops into voluntary grasp by 5 months; full pincer grasp by 1 year.

Purposeful Reaching

  • Develops from 3-4 months reaching for objects, with adjustment to sizing and texture (Rocha et al., 2013).

Dynamic Systems Theory

Conceptual Foundation

  • Development is a dynamic interaction of nervous system maturation, body capabilities, and environmental conditions.

  • Illustrates self-organization; e.g., infant kicking reflects adaptation to achieve specific goals.

Empirical Studies

  • Infants exhibit different kicking patterns when legs are constrained or free (Thelen, 1999).

Essay Question

Evaluation Task

  • Critically evaluate: "Childhood developments in object grasping can be accounted for by maturation theory."

References

  • Dosman, C. F., Andrews, D., & Goulden, K. J. (2012). Evidence-based milestone ages as a framework for developmental surveillance. Paediatrics & Child Health.

  • Numerous other studies supportive of developmental theories and milestones.