Chapters 11 & 12Adolescence

Psyc311 DevelopmentalDr. Wright

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Definition of Puberty• Pubertas – Latin word for “adult”• Narrow definition: The process by which

an individual becomes capable of reproduction.– The activation of the HPG/HPA axis

• Broad definition: The physical, psychological, and cultural changes that occur as the growing child transitions into adulthood.

Time Periods of Adolescence

• Early adolescence – 10 to 13 years old– Continues to be pushed earlier

• Middle adolescence – 14 to 17 years old

• Late adolescence (early adulthood) – 18 to 22 years old– Continues to be pushed later?

physical changes…Primary sex characteristics

• The body organs and reproductive structures and functions that differ between women and men.

• Gonads (testes and ovaries)Secondary sex characteristics

• Characteristics of the body that are caused by hormones, develop during puberty, and last through adult life.

• Changes in genitals/breasts/voice• Pubic/body/facial hair

Tanner Stages• Sexual maturation in girls

– Growth of breasts/pubic hair– Body growth– Menarche– Underarm hair/oil & sweat glands

• Age of onset: 7 – 13 years

Tanner Stages• Sexual maturation in boys

– Growth of testes/pubic hair– Body growth– Growth of penis/change of voice– Facial and underarm hair/oil & sweat

glands• Age of onset: 9.5 – 13.5 years

Rapid acceleration of physical growth• Adolescent growth spurt• 3.5 (girls) to 4.0 (boys) inches/year• ½ adult weight gained during adolescence

Changes in body composition• 3:1 muscle to body fat ratio for boys• 5:4 for girls• Emergence of sex differences in physical

performanceChanges in circulatory and respiratory

systems• Increase in size/capacity of heart and

lungs

Two Roles of HormonesOrganizational role (life-long):

– Modification of the organism early in life• primarily influencing its anatomy

– Organization/structure of CNS• “Feminine” vs. “masculan-ized” brain

Activational role (specific to puberty):– Structural “remodeling” of brain– Increase in salience of sexual stimuli, sexual

motivation – Development of secondary sex characteristics

Hormone Regulatory System

• Endocrine system• HPA axis

– Hypothalamus Pituitary gland Adrenals

– Corticosteroids– Regulates body’s response to stress

• HPG axis– Hypothalamus Pituitary gland Gonads

(Testes/Ovaries)– Sex Hormones (Androgens/Estrogens)– Regulates sexual maturation

The biological changes of puberty can affect the adolescent’s behavior in at least three ways

impacts of puberty• Self-esteem

– Body image• Moods

– Fluctuation of moods– Due to hormones or environment?– “Storm and stress”: myth or fact?

• Sleep patterns– Delayed phase preference– 9 hours: 1 am to 10 am

• Family relations– Transformation of parent-child bond

• Peer relations– Transformation of friendships, romantic relationships

Timing - individual Factors• Genetic factors

– Timing and tempo• Environmental factors

– Nutrition– Body weight– Health care– Exposure to hormones/chemicals– Family conflict– Stepfathers

Timing - group Factors• Comparisons across socioeconomic

groups– Impact of poverty– Dietary intake, health care, exposure to

disease• Comparisons across countries• Comparisons across time periods

– Secular trend

Early Maturation• Boys

– Early maturation positives• Popularity, higher self-esteem

– Early maturation negatives• Deviant, risk behaviors; more rigidity later

• Girls– Early maturation positives

• Popularity (cultural dependence)– Early maturation negatives

• Lower self-esteem, eating disorders, emotions, deviant behaviors

Late Maturation• Boys

– Late maturation positives• Higher levels of creativity, inventiveness

– Late maturation negatives• Low self-esteem, low social competence

• Girls– Late maturation positives

• Thinner build– Late maturation negatives

• Social withdrawal

Among the most important brain changes to take place at adolescence are those in the prefrontal cortex and limbic system.

The second wave….Longitudinal fMRI studies reveal:• Period of rapid synaptogenesis and

pruning– Comparable to 1st 3 yrs of life– Growth: starts with onset of puberty– Pruning: 1% of gray matter/yr – Increased myelination (back to front)

• Opportunity for massive cognitive growth and learning– Shift into Piaget’s formal operations

heightened arousal• Increased hormone activity

– estrogen & testosterone• Sexual stimulation• Social status conflict

• Increased neurotransmitter activity– Limbic system

• heightened emotional sensitivity/reactivity• norepinephrine

– Punishment/reward system• increased risk, stimulation-seeking behaviors• dopamine

– Fluctuations in mood• Serotonin

(Pre) frontal lobe development

• Final development of executive function– Planning/problem-solving– Impulse control– Seat of “sober 2nd thought”

• Processing of emotions– Understanding/responding to emotions

• Full Maturation – sometime between adolescence and early adulthood

• Coincides with child-onset schizophrenia– Failure in executive functioning

Timing of brain maturation• Limbic system matures early in puberty• Prefrontal cortex matures several years later

• Heightened need for reward/stimulation– leads to increased stimulation-seeking behaviors

• Underdeveloped “sober” assessment of risks• Increased cognitive/social demands

– Creates cognitive overload– Difficulty with impulse control

• Time gap may explain why adolescence is a period of heightened experimentation with risky behaviors– Increased violence

• kids under 18 account for 25 of violent crime in US– Drug & alcohol experimentation– Unsafe sexual activities

Adolescents whose prefrontal cortical development is less mature than normal are more likely to have conduct problems. Populations most at risk?

Social implications• What should the social attitudes

be about adolescent exposure to and involvement in high-stimulation/high-risk activities?

• Sexual Activity• Drugs & Alcohol• Violence

Teen pregnancy• 750,000 teens between 15-19 years old

become pregnant every year.– 2/3rds between 18-19 years old.

• African American teens have highest rate– 134/1,000 vs. 48/1,1000 Caucasian teenagers

• 57% end in birth (11% of all births in US)– 14% end in miscarriage– 29% end in abortion

• 82% of those pregnancies were unintended

risk factorsPhysical• Sexual maturation

– 4-5 years before psychological/emotional maturation

– Becoming longer as puberty starts earlier• Brain development

– Heightened activation of limbic system– Increased attraction to risky behaviors– Pre-frontal development incomplete

• SES factors– 50% of pregnancies occur in most impoverished

populations• Less opportunity for education• Less access to birth control• Reduced internal locus of control• Exposure to other risk factors

– drugs, alcohol, abuse, lack of parental monitoring• Desire for family/stability

consequences• Should we be concerned about this?• For teenage parents

– mother in particular• For baby• For families• For community• Methods of prevention?

Why is teenage pregnancy higher in the US?

Impact of substance abuse• Alcohol/drug abuse

– Greater potential impairment in learning– More widespread brain damage– Repeated exposure may effect path and

quality of development– Due to reduction in plasticity, this damage

cannot be corrected later!• So, does this mean all experimentation

with drugs/alcohol bad?

• Should we be worried about exposure to graphic violence through media?– Why or why not?