A Biological Component of Personality: Temperament

The Learning Reflection Journal is a compilation of weekly learning reflections you’ll independently write about across Weeks 2, 3, 5, 6 and 7. During each of the assigned weeks, you will write two paragraphs, each 300 words in length (i.e., 600 words total). The first paragraph will describe a topic that you found particularly interesting during that week and what made it interesting, and the second paragraph will describe something that you have observed occurring in the real world that exemplified that topic. Only one topic may be recorded in the journal for each assigned week and your observed real word occurrence must be clearly related to it.



A Biological Component of Personality: Temperament






Let’s look at how we can see this genetic impact through its effect on temperament. Just what is temperament? It refers to individual differences in behavioral inclinations that are biologically based and remain relatively stable over time. We can see these differences very easily in babies. Some are shy and slow to warm up to new situations while others are outgoing seemingly at ease and ready to explore novel situations. There are different models of temperament, but these four seem to garner the most agreement among personality theorists: activity, sociability, impulsivity, and emotionality.

A Unique Research Methodology: Twin Studies

Twin studies have long been used to link genetics to personality. Identical twins share the same genetic makeup due to the splitting of one fertilized ovum. Fraternal twins, on the other hand, who are the result of two separate eggs being fertilized at the same time, do not share any more of an identical genetic makeup than two siblings who are not twins. The Minnesota Twin Study revealed that even identical twins raised apart from each other share many of the same traits and habits. However, it has also been shown that twins raised apart from each other have less similarity of traits than those raised together. This suggests that there is an environmental influence also at work. Similarities in personality are greater in identical twins than fraternal twins.

It is important to note that twins and siblings do not necessarily experience the same upbringing. This diversity in how children in the same household experience the environment differently is called nonshared environmental variance. For example, the first born child is often treated differently than the last born child or a boy child may be treated differently than a girl. This results in a shared environment being experienced differently by each child.

Many studies have shown that schizophrenia can run in families and has a genetic link. Thus, if one has a schizophrenic parent or sibling the odds of schizophrenia rise. If one has an identical twin with the disease the odds rise even more dramatically. This correlation exists even if the twins were raised in different households. It is not clear; however, if schizophrenia is purely a genetic disease. Structural abnormalities of the brain have been found in those suffering from schizophrenia. Concordance or the probability of a match between identical twins is neither conclusive nor exclusive.

There is not much solid, noncontradictory research findings on a genetic link to homosexuality partly, due to the values and mores of society, which have served to stigmatize homosexuality. Twin studies have shown that homosexuality appears to have some biological foundation, but genes are not the whole answer. We cannot rule out the role culture and rearing may play. How can we look at homosexuality from an evolutionary perspective? Perhaps the kin selection hypothesis will give us an answer or perhaps there is some other answer that further research will yield.

Illness and Disease

Illness, environmental toxins, and drugs can all cause disturbances in our personality and behavior. Many of us have heard the expression mad as a hatter, but how many of you know that its origin is the result of hatters being poisoned by the mercury used to make the felt hats? This continual exposure to mercury led to brain damage and subsequent alterations of brain function and behavior. Even today children are still being poisoned by being exposed to lead and other toxic heavy metals. Lead is known to damage a child’s nervous system and impair both cognitive and behavioral function. This can translate into personality problems such as antisocial behavior. There are known personality changes associated with both illegal drugs such as cocaine and prescription drugs such as thyroid medications.

Diseases can also impact our personality and subsequent behavior. It is known that Vincent Van Gogh suffered from Meniere’s disease. This disease is an inner ear disorder whose symptoms include:

  • dizziness
  • nausea
  • disturbance in hearing

Alzheimer’s disease is a disease that mainly affects older persons. It is characterized by memory loss and behavioral changes. As the disease progresses profound personality changes are present right up to the loss of the personality itself. Strokes can also initiate serious changes in personality. Depending on the region of the brain that is damaged noted changes can be increased or decreased aggression and uncooperative behavior.


Biology and Environment Interactions

Biology can affect the environments we live in. A perfect example is a baby who continually cries and is difficult to soothe. Before very long the parents become increasingly frustrated and irritated. This leads to the infant now living in an environment of exasperation and vexation. This type of environment then influences our personality. The process is repeated with certain characteristics of temperament inclining us to particular experiences which will help shape our personality. This tendency to seek out certain types of environments is called tropism. We are either moving in the direction of health-promoting or health-threatening environs.

Does how we look uncover our personality? W.H. Sheldon expanded on the work of Ernst Kretschmer, a German psychiatrist who pondered if there was an association between physique and mental maladies. Sheldon measured people’s physical ratios and came up with a theory about how underlying physiological body type was related to the types of experiences we choose. His body types or somatotypes as he labeled them are endomorphs, ectomorphs, and mesomorphs.

The way other people react to how we look has a great influence on how we view ourselves. There has been much research done on correlating beauty with goodness, smartness, and kindness. This idea then influences how people treat us which in turn shapes our worldview and our personality.

Evolution of Social Behavior

Sociobiologists study the function of the evolution of social behavior. The attachment of a child to its primary caregiver is an example of a biologically based social behavior. Sociobiological analyses are most often applied to human aggression, mating rituals, and family interactions. The motivation to give preferential treatment to one’s own children over-step or adopted children is motivated by self-interest and the desire to enhance and preserve one’s own genetic matter. This is termed by sociobiologists as the Cinderella Effect.

Over time there has been much misuse and misinterpretation of knowledge in regard to genetics. One of the most misunderstood concepts is Charles Darwin’s idea about the survival of the fittest. Simply stated it proposes that the fittest individuals evolve and reproduce and those who are less able to compete well in their environment will be less likely to grow up and reproduce. It does not mean that weaker individuals and cultures should not survive. This idea of Social Darwinism prompted American immigration laws to exclude so-called inferior groups, the Nazi dream of a master race which led to genocide, and eugenics and the forced sterilization of different groups.

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