The Journey of Human Movement: From Blueprint to Walking
Introduction: The Unique Human Journey
The baby human takes the longest to mature among all animal kingdom creatures, undergoing a journey of movement exploration and mastering self-movement.
Heather, at just weeks old, is born with a genetic 'blueprint' for human movement, guiding development from head to toes.
Essential components for movement are innate, but the baby must actively unfold this blueprint.
Early, seemingly erratic gestures are rudimentary patterns for more complex actions, forging new neural pathways and kickstarting developmental processes.
The Stepping Pattern: An Early Mystery
Unlike other animals, human babies cannot stand and walk at birth.
Dale Darren, with support, can exhibit a 'stepping pattern' – heel-toe, alternating legs, unique to human babies.
This pattern appears to disappear around weeks (e.g., Ariana) and mysteriously returns months later, a long-debated phenomenon.
Dr. Esther Thelen's Research: Initially, scientists theorized a brain event reactivated the pattern.
Thelen wondered if gravity caused its disappearance.
Water Experiment: When Ariana was placed in water, her stepping pattern reappeared, suggesting water buoyancy countered gravity.
Treadmill Experiment (at months): Eli, needing support, showed the stepping pattern on a treadmill, proving it is never lost, only masked.
Thelen's Theory: Babies' legs are too heavy for their weak muscles to overcome gravity, making the pattern impossible to perform independently.
Kicking: Practice and Muscle Development
At months, babies excel at kicking, which is essentially the stepping pattern in a different position.
Importance: Kicking builds and strengthens leg muscles, preparing babies for future movement, like an athlete in training.
Understanding Intentional Movement: Thelen investigated how random kicking becomes controlled movement.
Mobile Experiment (with Mabel, months): Mabel's legs were tied by a ribbon to a mobile.
Initially, Mabel kicked unintentionally, and the mobile moved.
She soon made the connection that her kicking made the mobile dance.
This understanding led to more intense kicks; Mabel realized she could direct her leg movements and control her environment.
Babies, like adults, derive pleasure from control.
Rolling Over: Gaining Environmental Control
At months, babies like Liam have limited control, relying on others for movement and position changes.
Challenges: Liam struggles to lift his head due to its large size and weak neck muscles, despite performing 'push-ups'.
Motivation: Frustration (e.g., lying on belly unable to see) drives the desire to change position.
Achieving Rolling (Mitchell, months): Months of kicking and modest 'push-ups' strengthen leg and back muscles.
Mitchell eventually lifts his legs and rolls over for the first time.
This milestone allows him to control his view, opening a 'new world of wonder' but also introducing unforeseen dangers.
Reaching: Active Interaction with the World
Grasping Reflex vs. Reaching: Babies are born with a grasping reflex (can clasp but not let go).
Coordinated reaching requires significant physical and mental development.
Early Limitations (Rowan, months): Rowan desires a toy but cannot coordinate arm movements.
Thelen's Insights into Reaching: Arms have many degrees of freedom, making coordination difficult.
Foot Reaching: Thelen discovered infants can reach with their feet first, as feet have a more limited range of movement and are easier to control (similar to other primates).
Developing Hand-Eye Coordination (Anna, months): In one month, Anna makes a huge leap, finding the muscle pattern for reaching, guided by her eyes.
Objects are brought in for closer examination, typically with the mouth.
Adapting to Situations (William, months): Babies learn to adjust to different situations.
If one hand is restrained, William discovers a new strategy: reaching across his body with the other hand.
This self-discovery is driven by desire, not taught.
Cognitive Significance: Reaching signifies a change in understanding the world.
'Desire is born,' and the external world becomes within their grasp.
Babies learn to gauge space and distance, improving hand-eye coordination.
Each new reaching movement stimulates brain activity, exploring new colors and textures.
Sitting Up: A New Perspective and Independence
Milestone (Caitlin, months): Learning to sit expands the baby's horizon.
Challenges: Sitting requires significant balance and strong torso muscles; initially, hands are needed for support.
Benefits: Control over visual input, seeing farther, and a dawning sense of herself as an independent being.
Balance Issues: Infants are 'top-heavy' with a high center of gravity, prone to toppling.
Mastering Posture: Each motor development stage requires mastering a new posture, teaching perseverance.
Reaching While Sitting: Maintaining balance while reaching in any direction is a complex task requiring coordinated head, arm, eye, and leg movements.
Nathaniel ( months): Tracked by a computer, he struggles to coordinate locating a toy, assessing reach, lifting his arm, and stabilizing his head and trunk.
Kitty (a few weeks older): Has mastered sitting.
She plans her reach, stabilizes her hands and trunk, sways to maintain balance, makes adjustments, and successfully reaches.
Discriminates, only reaching for desired toys.
Crawling: Freedom and New Dangers
Transition (Lucas, months): From sitting, Lucas is frustrated, which propels him into crawling. He finds himself on all fours.
Early Challenges: Lucas initially moves backward, but this is part of learning.
Mastering Crawling (Madeleine, months): Strong enough to push up on all fours, the perfect posture for exploring.
Needs practice; may prefer communicating from a distance initially.
Variety of Styles: Jacob demonstrates one of recognized crawling postures.
Declaration of Freedom: Crawling brings new goals, happiness, allows sharing treasures, and discovering secret places.
New Dangers: Crawling babies ('new crawlers') often get into trouble.
Developmental psychologists once thought fear of heights was innate, but new crawlers like Iran don't show it.
They don't understand the danger of staircases.
Learning About Gaps and Heights: Karen Adolph's Research
New Postures, New Lessons: Each new posture (lying, sitting, crawling) brings new lessons and obstacles.
Transfer of Learning: Dr. Karen Adolph investigated if infants transfer learning about abilities from sitting to crawling.
Gap Experiment (Ethan, months):
Sitting: Ethan, experienced in sitting, knows his limits and refuses to reach across a gap that's too wide.
Crawling: As a new crawler, Ethan lacks understanding of the gap's implications while crawling. He misjudges its width and depth, recklessly plunging in.
Conclusion: Babies must relearn limits and dangers in each new posture to survive childhood.
Jane's Learning: After falling once, Jane ( months) cleverly seeks alternatives and refuses to cross the gap.
Experience and Movement: Learning about height and depth is linked to active, self-directed movement.
The Visual Cliff and Peripheral Vision (Dr. Joe Campos's Lab)
Visual Cliff Experiment: A plexiglass surface with one solid half and one transparent, seemingly deep half.
Kaitlyn (new crawler): Sees depth but happily crosses the 'abyss,' not understanding its danger.
Reese (crawled for a few weeks longer): Reacts with classic fear of heights, refusing to cross despite her mother's calls.
Conclusion: The difference is the amount of crawling experience.
Fear of Heights and Peripheral Vision: New research suggests fear of heights is linked to the development of peripheral vision during crawling.
Moving Room Experiment: Two infants with different crawling experiences.
Emmet (very new crawler): Focuses forward. When walls move, he doesn't notice the peripheral information and doesn't experience the illusion of self-motion that adults would.
Emmeline (lots of crawling experience, months): Reacts strongly to wall movement, adjusting her body to maintain stability. Her active crawling experience has made her sensitive to peripheral vision, leading to a healthy fear of heights.
Pre-Crawlers and Controlled Movement (Dr. David Anderson's Work)
Toy Car with Joystick Experiment: Tests if pre-crawlers can learn about peripheral vision and heights.
Alexis (first session): Treats the joystick as a toy, making no connection to car movement.
Lucy (second session): Understands the car moves but struggles to operate the joystick, eventually making the connection.
Colin (previous training): Quickly rediscovers the joystick's purpose.
He notices movement past walls through his peripheral vision while facing forward, gaining a sense of control over his movements.
Impact on Depth Perception (Colin on Visual Cliff, weeks later):
After car training, Colin (now a new crawler) is put on the visual cliff.
Despite being a new crawler, he refuses to cross the deep side, exhibiting fear.
Conclusion: His training in controlling movement in the car increased his attention to peripheral vision, leading to an understanding of what depth implies.
Wisdom from Controlled Mobility: It's not just the physical act of crawling, but the control over mobility that teaches infants wisdom and allows them to navigate the world more safely.
Iran's Re-evaluation: Weeks later, Iran (now a confident crawler) approaches a staircase. He tests his limits, but understanding depth and height, he reverts to crawling due to perceived danger, rather than attempting two feet.
Emotional Aspects of Mobility
Anxiety of Freedom: Newfound freedom from crawling comes with emotional price.
Max's Shopping Trip: Max (crawler) explores but becomes anxious the further he crawls from his mother, needing reassurance.
Emotional Refueling: Psychologists call this