Week 2 - Motor Development

Motor Development

Learning Outcomes

  • Distinction between Reflexes and Intentional Movements

    • Understanding the essential differences between involuntary reflexes and voluntary movements.

  • Typical Gross Motor and Fine Motor Development

    • Explaining the expected physical skills related to both gross and fine motor development.

  • Maturation Theory and Dynamic Systems Theory

    • Understanding and explaining these theories with respect to supporting literature.

Key Questions

  • Do early motor skills form the basis for later, more complex motor skills?

  • How do new motor skills develop?

Gross Motor Milestones

Major Milestones

  • Newborn:

    • Exhibits Moro reflex, positive support primitive reflex, and flexed posture.

  • Two Months:

    • Capable of lifting head up to 45° in prone position.

  • Four Months:

    • Displays asymmetrical tonic neck reflex; lifts chest while in prone position.

  • Six Months:

    • Primitive reflexes disappear; child can pull to sit; sits with tripod support.

  • Nine Months:

    • Postural reflexes present; rolls both directions; sits well without support.

  • Twelve Months:

    • Moves to sit; begins crawling; pulls to stand; may walk with assistance; able to catch a rolling ball.

  • Eighteen Months:

    • Stands independently while walking; navigates stairs with railing assistance.

  • Twenty-Four Months (Two Years):

    • Capable of running, jumping, and kicking; throws a ball overhand about three feet; walks up stairs while marking time without railing.

  • Thirty-Six Months (Three Years):

    • Can pedal a tricycle; navigates stairs while alternating feet with no railing.

  • Forty-Eight Months (Four Years):

    • Hops; walks down stairs alternating feet; walks backward in a line.

  • Sixty Months (Five Years):

    • Catches a ball; demonstrates balance on one foot; performs sit-ups; can skip.

Reference: Dosman et al. (2012)

Reflexes

Definition of Reflexes

  • Reflexes: Involuntary, rapid movements in response to a stimulus.

    • Function: Help organisms avoid danger.

    • Examples of such reflexes include:

      • Withdrawal Reflex

      • Blinking Reflex

      • Coughing Reflex

Reflexes in Infants

  • Stepping Reflex: Early movement potentially linked to walking.

  • Asymmetric Tonic Reflex: Triggered by head turn, known as the “fencing” reflex.

  • Grasping Reflex: Elicited by stroking the palm.

  • Moro Response: Startle reflex due to loud sounds or sudden movements.

  • Rooting Reflex: Triggered by stroking the cheek.

  • Babinski Reflex: Occurs when the sole of the foot is stroked.

Types of Reflexes

  • Primitive Reflexes

    • Controlled by the medulla and midbrain.

    • Key reflexes: Moro and Babinski.

    • Disappearance expected by 6-8 months—persistence may indicate neurological issues.

  • Adaptive Reflexes

    • Disappear during the first year, crucial for survival.

    • Includes sucking, swallowing, and rooting reflexes.

    • Weak or absent reflexes may indicate possible neuronal development problems.

Body Growth

Growth Rates and Patterns

  • A child's body grows more rapidly in the first two years than at any other life stage.

    • Average Height and Weight Statistics:

    • Newborn: 20 inches long, 7.5 pounds

    • End of Year 1: 32 inches (50% increase), weight triples to 22 pounds

    • End of Year 2: 36 inches (75% increase), weight quadruples to 30 pounds

Reference: Table from Berk (2019)

Growth Patterns

  • Cephalo-Caudal Pattern: Growth from head to tail; head is 1/4 of body length at birth, lower body grows later.

  • Proximo-Distal Pattern: Growth from center to limbs; head, chest, and trunk grow before arms and legs prenatally.

Maturation Theory

  • Motor development mirrors the cephalo-caudal pattern (Gesell & Ames, 1940).

    • Major milestones: Head control, reaching, sitting, walking.

    • Key Quote: "Development is controlled by a maturational timetable… Each animal species has its own sequence, and experience has little, if any, effect on motor development." (Slater & Bremner, pp. 47).

Development of gross motor skills

  • Supine - newborn complete head lag, 3mo slight head lag, 4-5mo no head lag, 5-6mo sit supporting self, 6-7mo sits without support,

  • Ventral suspension - newborn lack of head control, 6 weeks momentarily hold head in same place - 8 weeks maintain head in line with body, 3mo maintain head above line

  • prone - newborn lack of head control, 6 weeks momentarily holds head in same place as rest of body, 3mo holds chin and shoulder off surface

Variability in Motor Development

Sources of Variability

  • Intrinsic Factors:

    • Genetic attributes and physical characteristics, including temperament.

  • Extrinsic Factors:

    • Environmental influences, socio-economic status, family background, and cultural contexts.

Fine Motor Skills

Major Milestones

  • Newborn: Exhibits rooting and sucking reflexes; orients to sound; smiles in response to voice; variable in cries.

  • Two Months: Gurgling sounds present.

  • Four Months: Coos; vocalizations show development.

  • Six Months: Looks toward speaker; vocalizes in response; laughter observed.

  • Nine Months: Transfers objects, utilizes radial-digital grasp, and performs raking pincer grasp.

  • Twelve Months: Mastery of pincer grasp; voluntarily releases cubes into a cup; can hold a bottle.

  • Eighteen Months: Stacks 2-3 cubes; scribbles; self-feeding using fingers.

  • Twenty-Four Months (Two Years): Copies vertical lines; stacks six cubes; uses a spoon; helps with dressing.

  • Thirty-Six Months (Three Years): Copies horizontal lines and circles; stacks ten cubes; uses utensils well; drinks from an open cup; removes socks and shoes.

  • Forty-Eight Months (Four Years): Copies cross shape; draws 2-4 part figures; cuts paper in half; dresses with no buttons.

  • Sixty Months (Five Years): Copies square shape; draws a 10-part figure; colors within lines; masterful tripod pencil grasp; thoroughly washes and dries hands.

Reference: Dosman et al. (2012)

Characteristics of Fine Motor Skills

  • Involves precise movements using the hands and fingers, including the pincer grasp.

  • Necessitates eye-hand coordination and the ability to manipulate small objects.

  • Linked with visuo-spatial skills that encompass both motor and cognitive domains (Gerber et al., 2010).

Development of Grasping Skills

  • Newborn: Exhibits grasping reflex.

  • 3-4 months: Begins ulnar grasp (no thumb involvement).

  • 5 months: Grasps objects voluntarily.

  • 4-6 months: Adapts ulnar grasp according to object shape and size.

  • 1 Year: Transition to pincer grasp.

Reaching and Grasping

  • Study conducted by Rocha et al. (2013) observed that infants adapted their reach and grasp based on object size and texture from 4 months of age.

Development of Pencil Grasp

  • 10 months: Mastery of pincer grasp.

  • 12-15 months: Palmar supinate grasp observed.

  • 2-3 years: Digital pronate grasp evident.

  • 3-4 years: Quadruped grasp observed.

  • 5-6 years: Tripod grasp established as the ultimate pencil grasp.

Purposeful Reaching Development

  • Newborn: Exhibits pre-reaching behaviors.

  • 3-4 Months: Demonstrates purposeful reaching.

  • 4-5 Months: Capability to transfer objects between hands.

  • 5-6 Months: Reaches for objects even in darkness.

Research Insights on Reaching

  • Infants were observed longitudinally (5-, 6-, and 7-month intervals) adjusting their hand orientation based on the object's position, as recorded by Witherington (2005).

Experiment Findings

  • Infants at 5, 7, and 9 months reached for a rod with internal lights, demonstrating continued attempts even when the object was not visible post-reach (McCarty & Ashmead, 1999).

Motor Development and Cephalo-Caudal Pattern

  • Study on 8-15 week-olds found that hands developed faster in reaching than feet, with the timing differences noted in Galloway & Thelen (2004):

    • Hands: 15.7 weeks for extended contact.

    • Feet: 11.7 weeks for extended contact.

Teratogen Exposure and Effects

Impact of Alcohol Consumption in Pregnancy

  • Research indicates prenatal alcohol exposure is significantly linked to developmental issues in motor control (Barr et al., 1990).

    • A study analysing pregnant women's reported substance consumption found negative effects on motor skills by age four, demonstrating risks persisting throughout pregnancy (Doney et al., 2014).

Dynamic System theory

  • standing, walking, pincer grasps are building blocks of more complex sequence actions, separate abilities blend together to become more complex and more effective

Thelen & Spencer (1998) - motor developments result from on going and dynamic interaction between:

  • Developments of the nervous system

  • Capabilities of the body

  • Environmental constraints and support

Critical idea is that these all interact to allow the development of the optimal movement for a particular situation.

Self-organisation within the system!\

Supporting research

3-month old infants tested

Free condition: Ribbon attached to one leg, made an overhead mobile move.

Infants quickly learned to kick legs, independently to move the toy.

Yoked condition: Both legs yoked together. Infants learned to kick both legs together to move the toy.

Natural kicking pattern adapted to

Exam Questions

  • Question Scenario:

    • Discuss potential teratogenic effects on an unborn baby concerning alcohol and nicotine, delays in developmental milestones, and interpret results using Dynamic Systems Theory.

    • Importance of timing in teratogen exposure, along with a lay summary (200 words) clearly labeled.

References

  • Barr, H. M., Streissguth, A. P., Darby, B. L., & Sampson, P. D. (1990). Prenatal exposure to alcohol, caffeine, tobacco, and aspirin: Effects on fine and gross motor performance in 4-year-old children. Developmental Psychology, 26(3), 339-348.

  • Doney, R., et al. (2014). Fine motor skills in children with prenatal alcohol exposure or fetal alcohol spectrum disorder. Journal of Developmental & Behavioral Pediatrics, 35(9), 598-609.

  • Dosman, C. F., Andrews, D., & Goulden, K. J. (2012). Evidence-based milestone ages as a framework for developmental surveillance. Paediatrics & Child Health, 17(10), 561-568.

  • Galloway, J. C., & Thelen, E. (2004). Feet first: object exploration in young infants. Infant Behavior and Development, 27(1), 107-112.

  • Gerber, R. J., Wilks, T., & Erdie-Lalena, C. (2010). Developmental milestones: motor development. Pediatrics in Review, 31(7), 267-277.

  • Gesell, A., & Ames, L. B. (1940). The ontogenetic organization of prone behavior in human infancy. The Pedagogical Seminary and Journal of Genetic Psychology, 56(2), 247-263.

  • Lester, B. M., & Tronick, E. Z. (2004). The neonatal intensive care unit network neurobehavioral scale procedures. Pediatrics, 113(Supplement 2), 641-667.

  • McCarty, M. E., & Ashmead, D. H. (1999). Visual control of reaching and grasping in infants. Developmental Psychology, 35(3), 620-631.

  • Rocha, N. A. C. F., et al. (2013). Adaptive actions of young infants in the task of reaching for objects. Developmental Psychobiology, 55(3), 275-282.

  • Slater, A., & Bremner, J. G. (Eds.). (2017). An introduction to developmental psychology. John Wiley & Sons.

  • Thelen, E. (1994). Three-month-old infants can learn task-specific patterns of interlimb coordination. Psychological Science, 5(5), 280-285.

  • Thelen, E., & Spencer, J. P. (1998). Postural control during reaching in young infants: A dynamic systems approach. Neuroscience & Biobehavioral Reviews, 22(4), 507-514.

  • Witherington, D. C. (2005). The development of prospective grasping control between 5 and 7 months: A longitudinal study. Infancy, 7(2), 143-161.