Temperment
In psychology, “temperament” refers to the personality tendencies that we show at birth (and that are therefore biologically determined). For example, Thomas and Chess (1977) found that babies could be categorized into one of three temperaments: easy, difficult, or slow to warm up. After birth, environmental factors (such as family interactions) and maturation interact with a child’s temperament to shape their personality (Carter et al., 2008).
Research suggests that there are two dimensions of our temperament that are important parts of our adult personality: reactivity and self-regulation (Rothbart, Ahadi, & Evans, 2000). Reactivity refers to how we respond to new or challenging environmental stimuli; self-regulation refers to our ability to control that response (Rothbart & Derryberry, 1981; Rothbart, Sheese, Rueda, & Posner, 2011). For example, one person may immediately respond to a new stimulus with a high level of anxiety while another barely notices it.(2)
Genes and Personality
In the field of behavioral genetics, the Minnesota Study of Twins Reared Apart—a well-known study of the genetic basis for personality—conducted research with twins from 1979 to 1999. In studying 350 pairs of twins, including pairs of identical and fraternal twins reared together and apart, researchers found that identical twins, whether raised together or apart, have very similar personalities (Bouchard, 1994; Bouchard, Lykken, McGue, Segal, & Tellegen, 1990; Segal, 2012).(2)
These findings suggest the heritability of some personality traits, implying that some aspects of our personalities are largely controlled by genetics. Multiple twin studies have found that identical twins do have higher correlations in personality traits than fraternal twins. While identical twins may have some similar personality traits, however, they still have distinct personalities, suggesting that genetics are not the only factor in determining personality. One study measuring genetic influence on twins in five different countries found that correlations for traits between identical twins were 0.50 (i.e., they had 50% of traits in common), while for fraternal twins were about 0.20 (i.e., they had 20% of traits in common). These findings suggest that heredity and environment interact to determine an individual’s personality.(2)
It’s important to point out that traits are determined not by a single gene, but by a combination of many genes, and also by environmental factors that control whether certain genes are expressed. Many personality studies today investigate the activation and expression of genes and how they relate to personality. How DNA interacts with the environment determines what part of the DNA code is actually activated within an individual—in other words, which genes will be expressed. These small changes in individuals’ DNA help determine each person’s uniqueness—their distinct looks, abilities, brain functioning, and other characteristics that all work together to form a cohesive personality.(2)
The Brain and Personality
The biological approach to personality has also identified areas and pathways within the brain that are associated with the development of personality. A number of theorists, such as Hans Eysenck, Gordon Allport, and Raymond Cattell, believe that personality traits can be traced back to brain structures and neural mechanisms, such as dopamine and seratonin pathways. Researchers using a biological perspective will seek to understand how hormones, neurotransmitters, and different areas of the brain all interact to affect personality.(2)
One of the first documented cases that demonstrated the link between personality and the brain was that of Phineas Gage. In 1858, Gage was working as a blasting foreman for a railroad company. Due to a faulty blast, a railroad spike was blown through his head; miraculously, he survived the accident.(2)
The spike pierced Gage’s frontal lobe, and Gage experienced many subsequent changes in aspects of personality that we now know are associated with this area of the brain. The changes in Gage’s personality after his brain injury spurred interest in the biological factors involved in personality and implicated the frontal lobe as an important area associated with higher-order personality functions.(2)
Limitations of the Biological Perspective
A limitation of this perspective is that it focuses almost exclusively on the nature side of the nature vs. nurture debate (the debate about whether genetics or environment are more influential in human development). Because of this exclusive focus, other factors that are integral to personality are not included. Hormones, neurotransmitters, and genetics are the key factors in this focus; the effects of environmental and social factors, however, are often overlooked. Twin studies have shown that heritable factors are not the only predictor of personality or even diseases such as schizophrenia; the biological perspective does not fully address non-heritable factors.
Strengths of the Biological Perspective
One strength of the biological perspective is its strict adherence to scientific methodology. All factors are reduced to quantifiable variables that can be reliably measured by personality trait models and questionnaires. The personality measures are standardized across measurements, and these measures of personality are very compatible with statistical analyses, providing an easily administered and measurable definition of personality.(2)
This method can also be deterministic, meaning that some factors are identified as causal—i.e., certain brain structures or patterns may be identified as causing certain psychological outcomes. Because of this, the biological perspective can be useful in identifying causes of and effective treatments for personality and mood disorders. For example, identifying seratonin imbalance as a cause of depression led to the development of selective seratonin reuptake inhibitors (SSRIs), which have been found to be an effective treatment for depression.(2)
One strength of the biological perspective is its strict adherence to scientific methodology. All factors are reduced to quantifiable variables that can be reliably measured by personality trait models and questionnaires. The personality measures are standardized across measurements, and these measures of personality are very compatible with statistical analyses, providing an easily administered and measurable definition of personality.(2)
This method can also be deterministic, meaning that some factors are identified as causal—i.e., certain brain structures or patterns may be identified as causing certain psychological outcomes. Because of this, the biological perspective can be useful in identifying causes of and effective treatments for personality and mood disorders. For example, identifying seratonin imbalance as a cause of depression led to the development of selective seratonin reuptake inhibitors (SSRIs), which have been found to be an effective treatment for depression.(2)
Limitations of the Biological Perspective
A limitation of this perspective is that it focuses almost exclusively on the nature side of the nature vs. nurture debate (the debate about whether genetics or environment are more influential in human development). Because of this exclusive focus, other factors that are integral to personality are not included. Hormones, neurotransmitters, and genetics are the key factors in this focus; the effects of environmental and social factors, however, are often overlooked. Twin studies have shown that heritable factors are not the only predictor of personality or even diseases such as schizophrenia; the biological perspective does not fully address non-heritable factors.
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