Physical Development in Adolescence

The Biological Perspective

  • Jean Jacques Rousseau (18th Century Philosopher):
    • Believed the biological upheaval of puberty triggers heightened emotionality, conflict, and defiance of adults.
  • G. Stanley Hall (1904):
    • Described adolescence as a cascade of instinctual passions, resembling an era when humans evolved from savages to civilized beings.
  • Anna Freud (1969):
    • Viewed adolescence as a biologically based, universal "developmental disturbance."
    • A stage of powerful sexual impulses causing psychological conflict and volatile behavior.
  • These ideas are widely held in many western, contemporary societies.

The Social Perspective

  • The overall rate of serious psychological disturbance rises only slightly from childhood to adolescence, affecting 15-20% of teens.
  • Margaret Mead (1928):
    • Suggested that the social environment is entirely responsible for the range of teenage experiences (studies of Pacific Island teens).
  • The context, community, and culture greatly influence behaviors during puberty.
  • Consider contemporary influences on teen behavior and emotional turmoil.

A Balanced Perspective on Puberty

  • Biological changes associated with adolescence are universal.
  • The duration (length) of adolescence and associated responsibilities and demands varies significantly among cultures and societies.
  • Adolescence is extended in many industrialized, western societies, thus prolonging dependence on families and forestalling adulthood.
  • Three phases of contemporary adolescence:
    • Early adolescence (11-14 years):
      • Rapid and varied physical change
    • Middle adolescence (14-16 years):
      • Puberty nearly complete
    • Late adolescence (16-18 years):
      • Anticipated assumption of adult roles

Hormonal Changes

  • Pituitary gland releases growth hormone (GH) and stimulates other glands to produce hormones that bring body maturity.
    • Secretions of GH and thyroxine (thyroid gland) increase, eventually leading to gains in body size and skeletal maturity.
  • Hormonal changes are initiated and regulated by the hypothalamus, located at the base of the brain near the pituitary gland.
  • Estrogens (female hormones) and androgens (male hormones) are present in each gender, but in varying amounts.
  • Sex hormones increase long before physical changes are observable, at 6 to 8 years of age when the adrenal glands on top of each kidney start to release increasing level of adrenal androgens, call adrenarche.

Hormonal Influences - Feedback Loop

  • The hypothalamus stimulates the pituitary gland to release hormones that either induce growth directly or stimulate other endocrine glands to release growth-inducing hormones (red lines).
  • A highly sensitive feedback loop exists in which the hypothalamus detects hormone levels in the bloodstream and instructs the pituitary gland to increase or decrease the amount of each hormone accordingly (blue lines).

Body Growth

  • Testosterone leads to muscle growth, body and facial hair, and other male sex characteristics.
    • Androgens (especially testosterone) exert a GH-enhancing effect, contributing greatly to gains in body size.
  • Pubescent body growth approximately begins in females at age 10 years and in males at age 12 years.
    • Body growth is generally complete at 16 years for females and 18 years for males.
  • During adolescence, gains in height are 10-12 inches and weight gain is 50 to 75 pounds.
  • Body proportions and fat-to-muscle composition vary according to many factors including gender.

Motor Development & Physical Activity

  • Female body growth and motor development can best be described as ”slow and steady.”
  • Male body growth and motor development comes in “growth spurts.”
  • Physical activity levels decline markedly during adolescence in many nations, including the United States.
  • A study of children from 9 to 17 years of age, daily free-time physical activity diminished with age, more so for girls than boys.
    • Only a small percentage engage in regular exercise outside of school hours.
  • Sports and consistent exercise benefit cognitive and social development, plus limits the rise of teens who are overweight or obese.

Sexual Maturation

  • Reproductive organs (Primary Sexual Characteristics)
  • Observable body characteristics (Secondary Sexual Characteristics)

Sexual Maturation (continued)

  • Sexual maturation of adolescent females
    • Menarche, or first menstruation generally occurs among females in the US at age 12 years. The age range for this is very wide, 10 to 15 years of age.
    • For 12 to 18 months following the first menstruation, an ovum is not release from the ovaries. This is typical, but not absolute.
  • Sexual maturation of adolescent males
    • Observable body growth occurs quickly in males and peaks around 14 years of age.
    • Around 13 years of age, the spermarche or first ejaculation occurs due to the maturation of the prostate gland and seminal vesicles.
      • Early semen contains few living sperm, an early and initial period of reduced fertility. Again, this is typical but not absolute.

Individual Differences in Pubertal Growth

  • Nutrition & Diet
  • Exercise & Physical Activity Levels
  • Geographic Region
  • Socio-economic Status
  • Ethnicity
  • Physical Health
  • Emotional Well -Being
  • Family Experiences & Environment
  • Psychological Health – Safety & Security

Brain Development During Adolescence

  • Myelinated nerve fibers, white matter increases in the prefrontal cortex, the parietal lobes and the corpus callosum.
  • Neurons and supportive material, grey matter declines.
  • The corpus callosum, the cerebral cortex, including the prefrontal cortex, and the inner brain (amygdala and hippocampus) expand and attain rapid communication.
  • Adolescents gain diverse cognitive skills, including speed of thinking, executive function, and deliberate decision making. These advances are gradual.

Dual Systems Perspective on Adolescent Brain Development

  • The Prefrontal Cognitive-Control Network requires fine tuning during adolescence.
    • Teenagers’ performance on executive function tasks requiring inhibition of impulses, planning, and delayed gratification do not indicate full maturity.
  • Changes to the Emotional/Social Network:
    • Amygdala: plays a central role in processing novelty and emotional information
    • Ventral striatum: involved in processes of motivation and reward.
  • The Dual Systems Perspective suggests that the brain’s Emotional/Social Network outpaces the development of the Cognitive-Control Network, inclining teenagers toward heightened risk-taking and poor choices.

Changing States of Arousal

  • Sleep-deprived adolescents display declines in both cognitive and emotional self-regulation.
    • Likely to achieve less well in school, suffer from anxiety, emotional irritability, and depressed mood, and engage in high-risk behaviors.
  • Sleep rebound on weekends sustains a negative sleep pattern that leads to difficulty falling asleep on other evenings.

Reactions to Pubertal Changes

  • Parental relationships and Adult-Child Communication
  • Socio-economic differences are reported – accurate/inaccurate information
  • Females are more likely to discuss early menarche than males discussing their first spermarche.
  • In Western, contemporary societies few opportunities or ceremonies recognize the beginning of adulthood and acceptance of responsibilities afforded young adults.

Pubertal Change, Emotional and Social Behavior

  • Adolescent Moodiness
    • Higher pubertal hormone levels
    • Emotional challenges
    • Negative life experiences
    • Failure of the “cultural script”
  • Parent-Child Relationships
    • Rise in conflicts during adolescence
    • Decline in closeness
    • Humans are unique to many species, as we keep pubescent teens in the family structure.
    • Is the issue…CONTROL
    • Female adolescent conflicts with parents ARE MORE INTENSE.

Pubertal Timing

  • Early maturing males versus early maturing females
  • Cultural/community expectations
  • Emotional difficulties for both early and late maturing teens
  • Two factors:
    • How closely the adolescent’s body matches cultural ideals of physical attractiveness
    • How well young people fit in physically with their agemates.
  • The Role of Physical Attractiveness – body image/self-esteem
  • The Importance of “Fitting In” with Peers
  • Long-Term Consequences – Early maturing females at greatest risk; these challenges can persist well into adulthood. (Early 30s !?!?)