Motor Development in Infancy

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Term

Primitive reflexes

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Definition

Involuntary, stereotyped motor responses present at birth, mediated by the brainstem and spinal cord before cortical control is established. Key examples: Moro (startle) reflex — arms extend then flex in response to a sudden drop; rooting reflex — head turns toward cheek stimulation; palmar grasp — automatic gripping of objects placed in the palm; stepping reflex — walking-like leg movements when held upright over a surface; Babinski reflex — toes fan upward when the sole is stroked. Most disappear by 3–6 months as the cortex matures; their persistence beyond expected ages signals neurological concern.

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All 6 Terms & Definitions

Primitive reflexes
Involuntary, stereotyped motor responses present at birth, mediated by the brainstem and spinal cord before cortical control is established. Key examples: Moro (startle) reflex — arms extend then flex in response to a sudden drop; rooting reflex — head turns toward cheek stimulation; palmar grasp — automatic gripping of objects placed in the palm; stepping reflex — walking-like leg movements when held upright over a surface; Babinski reflex — toes fan upward when the sole is stroked. Most disappear by 3–6 months as the cortex matures; their persistence beyond expected ages signals neurological concern.
Cephalocaudal development
The directional principle that motor control develops from the head downward toward the feet. Head lifting (1–2 months) → rolling and sitting (4–7 months) → standing and walking (10–15 months). Mirrors the direction of prenatal neurological and muscular maturation.
Proximodistal development
The complementary principle that control develops from the body's midline outward to the extremities. Trunk control precedes arm coordination, which precedes precise finger movements. In grasping: whole-arm sweeping (3–4 months) → ulnar grasp → radial-palmar grasp → pincer grip (~8–10 months).
Dynamic systems theory (Thelen)
The view that motor skills are not pre-programmed in the nervous system waiting to be released by maturation, but emerge from the self-organisation of multiple interacting components — neural, biomechanical, motivational, perceptual, environmental. Classic evidence: leg-weighting and water-immersion studies showed that the stepping reflex "disappears" due to changing body mass ratios, not cortical inhibition.
Gross motor milestones (infancy)
Normative achievements in large-muscle control across the first year: prone head lift (~1–2 months), rolling back-to-front (~4–5 months), sitting without support (~6–7 months), crawling (~7–9 months), pulling to stand (~9–10 months), cruising (~10–11 months), independent walking (~12–15 months). Timing varies substantially across individuals and cultures; sequence is more consistent than timing.
Fine motor milestones (infancy)
Achievements in small-muscle, hand-based control: swiping at objects (~3–4 months), voluntary reaching (~4–5 months), bilateral transfer of objects hand-to-hand (~6–7 months), ulnar then radial-palmar grasp (~5–8 months), index-finger pointing (~9–10 months), pincer grip (~9–12 months). Fine motor development tracks the proximodistal gradient and is closely tied to visual attention.