Psyc 228 Unit 5 Chapter 9 & 10
1. Define menarche. Describe the average age of menarche over the last few decades. Why
is it changing? Describe the individual differences in pubertal timing. What are the risks
for early maturing girls and early maturing boys.
Menarche is the first menstrual period of human females, signalling the beginning of fertility. In
Canada, the mean age at menarche is approximately 12.72 years, with significant inter-
provincial difference in the onset. Out of all the socio-economic indicators, only income was
found to have a significant association with age at menarche. High income was associated with
lower early menarche rates but higher rates for late menarche.
The timing and experience of puberty vary widely among individuals but are often described in
three broad groups: early maturers, late maturers, and on-time maturers. Adolescents who
develop faster than average same-age peers are called early maturers. In turn, late maturers
develop more slowly than average, whereas on-time maturers experience pubertal maturation
at an average rate. These differences are due to genetic difference, as well as social and cultural
difference.
Studies report lower self-esteem, poorer body image, and higher rates of sexual promiscuity,
depression, smoking, and drinking among girls who mature early compared with their on-time
peers. Substance use is more prevalent among early maturing girls and boys, and this pattern is
seen across cultures. Compared with on-time and later-maturing boys, early maturing boys
reported more internalized distress and hostile feelings.
2. Summarize the key changes that occur in the adolescent brain in terms of grey and white
matter.
During adolescence, grey matter gradually decreases because of synaptic pruning. This decrease
happens in specific areas of the cortex, most notably the prefrontal cortex, which is responsible
for complex cognitive processes. Meanwhile, the same areas show a continuous increase in
white matter, largely due to increase amounts of myelin, the substance that speeds neural
connections. Changes in white matter are linked to language development, whereas the growth
of grey matter in the prefrontal cortex is linked to increases in executive functioning.
3. Describe growth in the skeletal system and the implications of growth spurts and
asynchronicity.
Adolescents’ behaviours tend to result in increased bone density. Their active lifestyle also leads
to increased risks to skeletal integrity. In other words, adolescents’ also experience a growth
spurt, during which height and weight suddenly increase. For boys the rate averages 10.4 cm a
year, and for girls 8.9 cm a year. The closing of the ends of the long bones signals the conclusion
of the growth spurt. The rate of girls’ height changes peaks at approximately age 12, whereas
boys continue their spurt until about age 18. Another aspect of bone growth during
