Understanding life stages and individual changes that may be attributed to these stages is an important part of psychology, and is an important component in what qualifies psychology as a science rather than an art (although arguably it is both). Human developmental psychology is particularly interested in nature vs nurture, are attributes genetic or a result of environmental factors. this post will introduce developmental psychology and the specifics of physical development. The topic of Growth and Lifespan Development is weighted at 12% and combines information from the topics of biological bases of behavior, cognitive-affective bases on behavior, and social and cultural bases of behavior, so it may be a good idea to start with these other topics before going into the section of growth and lifespan development. The information is best used in collaboration with your own knowledge and what you have already been taught, your previous notes or textbooks, and research if you need more information on a particular topic. Or you could check out the product reviews page.
Introduction to Developmental Psychology
Like many areas of psychology, developmental psychology has many theories with no real consensus on which theory is absolutely correct. These theories fall into 2 major categories of developmental change, those that believe that change is Qualitative (there are significant time frames in individuals lives, particularly childhood, where change progresses through specific stages and is abrupt and rapid) and those that believe change is Quantitative (development is continuous and change is a result of slow and steady growth and maturation). While theorists may differ on when these major life changes, for the most part there is agreement that not all life periods have the same impact and some are more important that others. These life periods can be described as either Critical Periods (If a particular developmental phenomenon does not occur at a specific time it will not occur at all, for example organ development during the embryonic stage of development) or the life period can be described as Sensitive Periods (there are certain time periods where development is favorable and most likely to be successful but is capable of forming at a different time, for example language development is most favorable in the first few years of life but is capable of developing later in life).
There are many influences on development, and to make it simpler to understand these influences are split into different categories (because we psychologists love categories!). It is generally understood that development comes from all categories rather than needing to choose which one has all the influence.
Genetic Influences: There are 23 chromosome composed of thousands
of genes, which are made up of DNA and RNA. The Genotype is the entire genetic makeup of an individual, and the Phenotype is the observable traits of a person. Abnormalities at a chromosoal level can result in a variety of genetic disorders. Twin studies have been helpful at determining the difference between genetic and environmental influences. Typically this is a continuum, where the genetic material gives the basic foundation for a specific trait (such as IQ) but environmental factors can greatly impact this presentation (poverty and abuse are often associated with diminished IQ scores).
Environmental Influences: Urie Bronfenbrenner divides environmentl inlfuences into 5 levels: The Microsystem is the environment the individual encounters on a daily basis such as school and home. The Mesosystem are the interactions between 2 or more microsystems, for example you introduce your spouse to your work colleagues. The Exosystem are the interactions between 2 or more settings, one of which the individual is not a part of. For example while a child may not go to the setting of their parents work, the parents workplace has an indirect affect on the child’s development. The Macrosystem are the systematic and cultural influences on an individual, including economical and political influences. The Chronosystem are life events and how changes in time affect the individual. This can include everything from changes in the microsystem (such as a parents divorce at a specific life stage) to changes in the macrosystem (such as war at a specific stage of life).
Normative Influences: Events that seem to be somewhat similar for the majority of people. Age-Graded events are those that are typically experienced around the same age for most people (for example puberty or retirement). History-Graded are similar to a particular generation of people (for example the technology boom or great depression).
Non-Normative Influences: These are atypical or unusual events that have a significant impact on development, or this can also include normative events that occur at an atypical time in an individuals life. For example a natural disaster such as Hurricane Katrina, or the death of a parent when an individual is still a fairly young child.
There are many facotrs that can influence prenatal development, much of which lies with the health and behaviors such as nutrition and substance use (alcohol, nicotine, and other illicit substances). Conception occurs when sperm combines with ovum to create a zygote, which the multiplies through cell division and develops into an embryo and then fetus during gestation. There are 3 stages:
Germinal Period: From conception to 2 weeks, the zygote divides multiple times and mobilizes towards the uterus until it has implanted in the uterus wall.
Embryonic Period: From 2 weeks up to 12 weeks, and involves the very quick process of major organ development. This is a very vulnerable time as the embryo is at risk of developing birth defects while the nervous, circulatory, respiratory and digestive systems are developed. Birth defects could be as a result of exposure to teratogonic agents (such as chemicals, medications, radiation or viruses known to cause birth defects).
Fetal Period: 12 weeks until birth, and involves rapid growth and more complex development of the organs. Typically development is cephalocaudal, that is from the top of the body down.
Early Childhood Development
There are 4 main areas of early childhood development:
Reflexes: There are specific involuntary movements that are present at birth for all healthy infants, and generally disappear after the first year of life. The Grasp Reflex is seen when an infant will firmly hang onto any object placed in its hand. The Rooting Reflex is in response to a babys cheek being stroked, the infant will turn their head and open their mouth and even start a sucking motion in preparation for being fed. The Babinski Reflex is when the foot is stroked and the baby will twist their foot and spread their toes. The Moro Reflex is the startle response, which involves extending the legs, arms, fingers and arching the back (imagine your response if you lose your footing and slowly start to fall backward).
Perceptual: This is in regard to the 5 sense and their course of development.
- Touch: This is the first sense to develop, and is more mature than any of the other senses. Infants actually feel pain right away and on the first day of life.
- Taste: Newborns prefer sweet over sour tastes, which is adaptive since breast milk is sweet and baby’s will spit out anything that does not taste good.
- Hearing: Hearing is developed by birth, and most likely well before birth. Research suggests that infants are able to distinguish speech from other sounds, and differentiate between familiar and new sounds.
- Smell: Smell is well developed at birth and infants can distinguish between the smell of their mother an another person.
- Vision: This sense is NOT well developed at birth, and improves quickly between 2 and 10 weeks, but does not typically reach 20/20 until 6 months to 2 years. Color perception is also poor until 4 months. Infants typically prefer faces and will fixate and follow faces over other stimuli.
Motor: Milestones in terms of motor development occur fairly consistently at the same age.
- 6 week: Baby can lift his/her head
- 4 months: Rolling over
- 7 months: Sitting alone
- 9 months: crawling and standing with support
- 12 months: standing alone
- 12-15 months: walking alone
- 16 months: walking up steps
- Preschool: Gross motor skill development
- School Aged: Perfection and smoothness of motor skills
The brain is the fastest developing part of the body in the early years and in the prenatal period. At birth the brain is already up to 1/3 developed, 3/4 by age 2, and 90% by age 5. After birth neurons grow and develop more axons and dendrite, and become more myelinated (a process that continues into an individuals 20’s). Synaptic strength improves with experience and the young brain has high plasticity up until about age 8. After this time brain functioning lateralizes to its specific hemispheres, and performance becomes more refined.
Adolescence is a significant time for development because on the onset of puberty. For females typically between the ages of 10 and 12 and includes the menarche (first menstral period), and for males typically between the ages of 12 and 14 and includes spermarche (first ejaculation). These changes in development mark the maturation of the sexual system and involve changes in hormonal secretion, which impacts secondary sexual characteristics such as body hair, growth spurts, breasts, deepening voice. The sexual system remains active until middle age when women typically between the age of 45 and 55 experience menopause (a decrease in estrogen and menstruation) and men experience male climacteric (a more gradual decrease in testosterone).
Adulthood & Aging
During adulthood there are very minor developmental changes that have been documented. As people age vision and hearing often declines, blood pressure increases, and there is some degeneration in the CNS. there are 2 types of aging: Primary Aging is what keeps us from living past a specific age (up to 110-120), and is thought to be due to either genetics or wear and tear on the body. Secondary Aging is aging as a result of disease or poor lifestyle and neglect of the body. in regard to the sexual systems, it is a myth that sex drive decreases with age, and after menopause and male climacteric the frequency of sexual activity is often similar to that of younger years.
There are many factors that influence health such as preventable disease factors, exercise, diet, demographics, substance use, obesity, and stress.
***We have to know this information for the EPPP, but can you see why it may be important for all psychologists to have an understanding of physical development? Any of this new information to you? Any significant developmental milestones you think were missed. Please share your thoughts in the comments below as this is useful for everyone studying!
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