Chapter 4: Infancy Physical Development

Changes in the infant brain

• Myelination

• Increased neural connectivity

• Tuning and Pruning

Myelination

The process of encasing axons with fat cells, begins prenatally and continues into adolescence and emerging adulthood; speeds up neural trasmissions

Increased Neural Connectivity

Connectivity among neurons increases, creating new neural pathways; facilitates the spreading of neural pathways in infant development

Tuning and Pruning

Connections that are used become stronger (“tuning”), while the unused ones are replaced or disappear— they are “pruned”

The experiences during infancy that affect the development of the brain

Advantages of an immature brain at birth

• High neuroplasticity; Adapts well to any culture or environment

• Safer childbirth due to smaller head size

• The prolonged period of brain growth allows humans to develop much higher-order thinking, language, and problem-solving skills than other animals

• Forces intense caregiving, building deep social and family bonds Disadvantages

Disadvantages of an immature brain at birth

• Total helplessness

• Vulnerability to environmental harm

• Prolonged prenatal dependency

• High metabolic cost

Dynamic systems theory

Motor development emerges from the continuous, cooperative interaction of multiple subsystems without requiring a top-down central controller

4 key aspects of the dynamic systems theory

• Nervous system maturation

• Strength

• Motivation

• Environmental support

Rooting reflex

Looking for food when touched on cheek

Sucking reflex

Automatically suck an object placed in mouth

Grasping reflex

Grab when middle of palm touched

Plantar grasp

When a finger is placed under the toes, the toes will curl

Babinski reflex

When the bottom of the foot is stroked from the heel upward along the outward part of the foot, the big toe bends back and the other toes fan or spread out

Crawling reflex

When the infant is placed on the stomach and pressure is applied to the sole of the foot, the infant will attempt to push against the hand and move the arms and legs in a crawling like motion

Tonic neck reflex

When an infants head is turned to a particular side, the leg and arm on that side will extend while the leg and arm on the opposite side will flex

Moro reflex

Arch back and stretch out arms when startled

Step reflex

When holding the infant upright with the legs and feet touching a surface the infant will move the legs like taking steps or walking

How developed is an infant’s vision at birth?

Vision is underdeveloped. Newborns can perceive light and dark, but they cannot discriminate between color differences until about 2–3 months.

How does a newborn’s visual acuity compare to an adults?

A newborn’s visual acuity is about 40 times worse than an adult’s.

What do objects look like to newborns?

Objects appear blurry, but newborns can detect bold patterns with sharp contrasts.

When does an infant’s vision become similar to an adult’s?

It can take about 6 months to 1 year for vision to become as good as an adult’s.

What is the visual cliff study?

A study designed to test whether infants perceive depth by placing them on a glass-covered surface that appears to have a drop-off.

What does infants’ preference for faces suggest about face perception?

It suggests there may be an inborn tendency to distinguish faces from non-faces.

What happened in the Cat in the Hat study?

Pregnant mothers read The Cat in the Hat during the last few months of pregnancy. After birth, their infants preferred listening to a recording of their mothers reading The Cat in the Hat rather than another story.

What two abilities did the Cat in the Hat study demonstrate?

The ability of the fetus to hear, remember, and learn before birth.

What tastes can infants distinguish at birth?

Infants can distinguish sweet, bitter, and sour tastes at birth.

What happened in the carrot juice study?

One group of pregnant mothers drank carrot juice, while a control group did not. After birth, infants exposed to carrot juice preferred carrot-flavored food/drink compared with infants who were not exposed.

What does the carrot juice study suggest about taste development?

Early exposure to flavors can influence infant taste preferences.

How does sensory development differ across vision, hearing, and taste?

Vision is relatively underdeveloped at birth, while infants already have important abilities in hearing and taste.