3: Developmental 3

Lecture Overview

• Today's lecture focuses on two key aspects of development: prenatal development and perceptual development.

• Emphasis on the timing of experiences in development.

Prenatal Development

Definition

• Prenatal development: the development from conception to birth (38-40 weeks).

Three Key Periods

1. Germinal Period (14 days)

   • Begins with conception; zygote forms when sperm fertilizes egg.

   • Ends when blastocyst implants in the uterine wall.

2. Embryonic Period (3rd to 8th week)

   • Major body parts and organs form.

   • Key developments:

     • Neural tube forms and closes (risk of conditions like anencephaly and spina bifida).

     • Heart starts beating by the 24th day.

     • Formation of limbs and facial features.

3. Fetal Period (9 weeks to birth)

   • Main period of growth and organ system refinement.

   • Sensitivity to stimuli; infants respond to light and sound.

   • Viability at 24 weeks, survival rate around 50%.

Teratogens

Definition

• Teratogens: agents that can cause malformations during prenatal development (e.g., drugs, diseases).

Examples of Teratogens

• Diseases: e.g., Zika virus causing microcephaly during the 2016 Olympics in Brazil.

• Drugs:

  • Thalidomide: caused limb malformations when taken for morning sickness in the 50s/60s.

• Environmental Agents: heavy metals that can harm development.

Effects of Teratogens

• The impact of teratogens depends on:

  • Dose and duration of exposure.

  • Timing of exposure, particularly during critical development periods.

Impact of Timing in Prenatal Development

• Timing is crucial as systems under rapid development are most vulnerable to teratogens.

• Example: Thalidomide babies show varying limb malformations based on when the drug was ingested in relation to limb development.

Fetal Alcohol Syndrome (FAS)

• Affects children whose mothers consumed alcohol during pregnancy.

• Characterized by:

  • Distinctive facial features (e.g., thin upper lip, smooth philtrum).

  • Central nervous system damage (leading to cognitive and behavioral issues).

  • Microcephaly (small head size).

Visual Development in Infants

Importance

• Vision develops significantly after birth, making it an interesting area of study.

• Infants initially have poor vision but can achieve adult-like acuity by 4-5 months.

Studying Visual Development

1. Visual Scanning Techniques

   • Eye tracking to study fixation and scanning patterns.

   • Infants prefer edges and high-contrast patterns due to poor visual acuity.

2. Habituation and Dishabituation

   • Infants lose interest in repetitive stimuli but respond to novelty (indicating they can differentiate).

3. Visual Preferences

   • Infants prefer faces and complex patterns, used to test visual acuity via Teller Visual Acuity Test.

Perceptual Narrowing

• Infancy is a sensitive period for distinguishing faces.

• Both the other species effect (ability to discriminate faces of non-human species) and the other race effect emerge as infants grow, influenced by typical visual experiences.

Impact of Lack of Visual Experience

• Animal studies (e.g., kittens with one eye sewn shut) illustrate critical periods. Missing visual experience can result in permanent impairment.

• Human infants with cataracts require early intervention to restore typical vision.