Biological events of puberty
Occurs usually between ages 8 and 14. For girls, the sequence of biological changes are as follows: 1) growth of nipples, 2) first pubic hairs, 3) height spurt, 4) first menstrual period (menarche), 5) final pubic-hair growth, 6) full breast development. Average age of menarche is 12 1/2 years. For boys, the sequence is as follows: 1) growth of testes, 2) first pubic hairs, 3) enlargement of penis, 4) first ejaculation of seminal fluid (spermarche), 5) height spurt, 6) final pubic-hair growth. Average age of spermarche is 13 years. For both, puberty is usually completed in about 4 years.
For girls, the usual sequence of physical changes in puberty is:
the beginning of breast development, the growth spurt, and menarche
For boys, the usual sequence of physical changes in puberty is:
growth of the testes; initial pubic-hair growth; growth of the penis; spermarche.
Hormone production is regulated deep within the brain, where biochemical signals from the hypothalamus signal the pituitary gland to produce hormones that signal the adrenal glands (above kidneys) to produce more hormones.
Pituitary activates the gonads, or sex glands (ovaries, testes). Hormone GnRH causes the gonads to increase production of estrogens and androgens (female and male sex hormones). Gonads are responsible for the marked sex differences in hormones.
Influences on the timing of puberty
Genes, body fat, hormones, and stress all affect the age. Genes on the sex chromosome have a marked effect on age. Girls develop ahead of boys. Girls are two years ahead of boys on height, but only a few months ahead on hormonal changes. Children with a large proportion of body fat experience puberty sooner. Hormones in the food supply have been said to be a reason why puberty is occurring early these days. Environmental chemical increase and decrease the production of testosterone and estrogen and affect appetite which could cause weight gain. The hormone leptin affects appetite. High levels are present at the onset of puberty. Affects appetite in females more than males and body fat is more closely connected to the onset of puberty in females than in males. Malnutrition delays puberty. Stress affects hormones by increasing their production causing puberty to occur earlier.
Nutrition and puberty
Body fat is needed to begin the process, but proper nourishment is needed once the body starts to grow rapidly. Deficiencies of important minerals such as iron, calcium, zinc are a problem in adolescence today.
A sudden uneven increase in the size of almost every body part. Proceeds from the extremities to the core. A height spurt follows the increase in body fat and then a muscle spurt occurs. Lungs triple in weight, heart doubles in size, blood pressure and volume rise, physical endurance increases. Height increase before muscles and internal organs. Young bones are more fragile than adult bones. Lymphoid system (tonsils and adenoids) decrease in size making teenagers less susceptible to respiratory problems. Skin becomes oilier, sweatier and more prone to acne. Hair becomes coarser and darker. Hairiness depends on genes and hormones.
Primary sex characteristics
Parts of the body that are directly involved in reproduction; vagina, uterus, ovaries, testicles, penis. During puberty, every sex organ grows and matures in response to increased hormone production.
Secondary sex characteristics
Physical traits that are not directly involved in reproduction but that indicate sexual maturity; man's beard, woman's breasts. Boys grow an average of 5 inches taller than girls and their shoulders widen, girls develop breasts and a wider pelvis and add on twice as much body fat as boys. Lower voice as the larynx grows, more noticeable in boys. These characteristics are more important psychologically.
Piaget's formal operational thought
The fourth and final stage of cognitive development, characterized by more systematic logic and the ability to think about abstract ideas. Ability to reason on the basis of "assumptions that have no necessary relation to reality".
One of the most prominent aspects of adolescent thought is the ability to:
think in terms of possibilities
Piaget's balance scale study
The heaviness of the weights and their distance from the center interact reciprocally to affect balance. This concept was completely beyond the ability of a 3-5 year old. By age 7, children realized that the scale could be balanced by putting the same amount of weight on each arm. By age 10, at the end of the concrete operational stage, they thought about the location but they used trial and error, not logic. They were able to balance different weights. By age 13 or 14, children hypothesized the reciprocal relationship between weight and distance, tested the hypothesis, and formulated the mathematical formula, solving the balance problem accurately and efficiently.
In Inhelder and Piaget's balance experiment, a child who systematically tests the idea that the relationship between weight and distance is reciprocal is probably age:
Piaget's 3rd eye study
Uses hypothetical thought which is reasoning that includes propositions and possibilities that may not reflect reality. Most 9 year olds would have a difficult time thinking about objects that don't exist or events that could never
happen. But when children entered the stage of formal operations, Piaget believed that they became very capable of considering hypothetical propositions and carrying them to a logical conclusion. The study showed that a 11 to 12 year old generates logical and creative responses to a hypothetical proposition and enjoy this type of reasoning.
Piaget's term for a type of adaptation in which new experiences are interpreted to fit into, or assimilate with, old ideas.
Piaget's term for a type of adaptation in which old ideas are restructured to include, or accommodate, new experiences.
Begins with an abstract idea or premise and then uses logic to draw specific conclusions. Capable by age 14 or so. Also called "top-down reasoning".
Reasoning from specific experiences or facts to a general conclusion. May be less cognitively advanced than deduction. Predominates through the school years, as children accumulate facts and personal experiences. Also called "bottom-up reasoning.
An aspect of adolescent egocentrism characterized by an adolescent's belief that his or her thoughts, feelings, or experiences are unique, more wonderful or awful than anyone else's.
An adolescent's egocentric conviction that he or she cannot be overcome or even harmed by anything that might defeat a normal mortal, such as unprotected sex, drug abuse, or high-speed driving.