Psych 125
Human Development
Christopher Gade
Office: 1031-G
Office hours: Tu 12-1:30 and by apt.
Email: gadecj@gmail.com
Class: T 1:30-4:20 Room 2210
Development After Birth
• When newborns enter the world, they differ from
their adult counterparts in a number of ways.
– Small size
– Imbalanced dimensions (head size, extremities)
– Underdevelopment (brain, muscle, bone)
– Different chemistry (hormones, neurotransmitters)
– Little ability to interact with their environment
Biology-Based Growth in Life
• Each of us grows in slightly different ways, but all
of us follow a fairly similar path. Moreover, we
develop biologically in a number of ways.
– Physical development (size,
proportion, content)
– Brain and nervous system
development (size, structure,
and function)
Basics at Birth
• Most newborns (95% of them born in the US) are
born between 18-22 inches long and 5 ½ to 10
pounds.
• Most exceptions to this are
due to external factors
– Mother’s diet
• video
– Mother’s smoking
– Genetic problems
– Prenatal problems
– Premature births
Tracking Physical Growth
• Infancy (0-2 years) – weight rapidly increases (2.5 –
5x), height increases (1.5 – 2x), and muscle mass
begins to increase
• Early childhood (2-6) – weight and height increase,
but slowly. Differentiation between individuals
becomes very noticeable (fat, muscle, height, weight)
– Exceptional differences in size are related to experience
• Diet (malnourishment and overeating)
• Growth hormone deficiency – the absence of deficiency of a
growth hormone produced in the pituitary gland
– Genetic, structural, stress related
• Prenatal experience (smoking, stress, other teratogens)
• Physical ailment (sickness, injury)
More on GHD
Tracking Physical Growth
• Middle and late childhood (6-11) – “dormancy” in
physical growth (1-2 inches and 5-7 pounds per
year). Muscle mass, bone development,
coordination, and better proportions mark this
stage of physical development.
Tracking Physical Growth
• Puberty (9/11 – 15/17) – massive amounts of
physical change occur due to a rush of hormones –
chemical substances secreted by the hypothalamus
and the pituitary gland.
– Reproductive growth (physical and capability growth)
– Height and weight growth (men = muscle, women = fat)
– Physical changes in voice (men), breast size, hair, skin, and
skeletal system
– Women = earlier and slower; estradiol (more overall
increase) and testosterone (2x)
– Men = later; testosterone (8x) and extradiol (small
increase)
– Note: the onset of puberty has been linked to social and
nutritional factors (diet, stress, etc.)
The Social Impact of Early Maturation
• Precocious puberty – the very early
onset and rapid progression of puberty
– Occurs much more often in girls than
boys (10x)
– Early development impact girls negatively
at the time
• Riskier behaviors, more emotional and social
problems
– And impacts girls negatively in the future
• Poorer school performance, life choices that
are similar to older peers, more time with
older peers, more emotional problems, more
drug and alcohol problems
– These same impacts don’t appear to
occur for boys
Tracking Physical Growth
• Post-puberty to adulthood to elderly age
– We grow until our early to mid twenties
– At around thirty our bodies begin to slowly decline
• More fat collects in specific areas
• We begin to shrink (men = 1 inch from 25 to 75, women 2 inches
from 25 to 75)
• We lose fat under our skin (wrinkles)
• Our skin loses its elasticity and becomes colored from experience
• Our muscle mass (sarcopenia) and elasticity also decline
• Out bone strength and density decrease
The Later Years of Change
• From the age of 50 on, the decline of the
physical body becomes much more rapid
– Females experience menopause
• Biological change – reproductive abilities, bone density,
muscle density
• Chemical change – estrogen (causes hot flashes, fatigue,
nausea, and other side effects)
– Physical appearance changes more rapidly
– Physical ailments become much more common
(cholesterol, circulatory, muscular, skeletal, lung
related)
– Note: Many of these changes can be offset to an
extent with both cognitive and physical exercise
Now onto another type of change
• Now that we’ve discussed how we progress
throughout life physically…
• In this next section, we’ll discuss how we
progress in our brain and nervous system.
Brain and Nervous
System Development
• At birth, our brains have
several important
characteristics to them.
– Structure – areas of the brain
that are associated with specific
functions
– Lateralization – halves of the
brain that are associate with
specific functions
– Neural plasticity – the ability for
the brain to adjust to physical
and environmental changes
More on Neural Plasticity
• At birth, our brain has nearly as many neurons
(60-100 billion) as we have in adulthood.
• The difference is, very few synapses between the
neurons are formed yet.
What causes this growth in connections?
• Experience based
formations
– Language example (more
activity in specific areas)
– Deprivation example (less
activity)
• Problem and growth
related rerouting
– Early damage example
(right hemisphere took
over control of language)
Other Growth-Related Changes in Our
Nervous System
• Myelination – the covering of the dendrites of
neuron cells with fat cells that speeds up the
communication process between neurons
– In class example
Growth During Childhood
• Synaptic “pruning” – the reduction in synapses that
begins at about 1 year of age
• Lobe development
– 3-5 frontal lobe growth (planning and organization)
– 5-15 parietal and temporal lobe (speech/language,
coordination, and spatial abilities)
Growth During Adolescence
• Development of the
amydala and limbic
system occur rapidly at
this stage
– Greater range of
emotions
– Stronger emotions
• Development of the
prefrontal lobe is very
slow (doesn’t complete
until around 25)
– Control of planning and
though
– Self-regulation and selfpreservation
The Decline in Adulthood
• As we age, our brains slowly
begin to lose weight (5-10%
from ages 20 to 90)
– Loss of synapses through
continued “pruning”
– Loss of myelination
– Possible loss of neurons
• Basic cell death
• Neurogenesis alternative
– Early findings of neurogenesis in the hippocampus and olfactory
bulb
– New attempts to prove that with exercise and challenge,
neurogenesis can occur throughout the brain
A Note on Brain Development and
Experience/Exercise
• Numerous studies have shown that exercise and
experience both play a role in the successful
function of the brain
– Video
• Greater synapse
density
• Greater blood flow to
cells
• Possible increase in
neurogenesis
That’s it for today…
• Reviewing:
– In this class we addressed how our bodies develop
physically
– We also discussed how our brains developed
physically
• Foreshadowing:
– In the next class, we look at the development of
health and health related problems