Evolution and Temperament: Biological Theories

Evolutionary Approaches

Evolutionary psychology applies natural selection principles to understand human psychology, including personality. It considers universal aspects of human nature, such as language, aggression, and sexual behaviors, while acknowledging that current circumstances may differ from those during evolutionary selection. Examples include evolutionary explanations of differences in personalities between men and women and evolutionary explanations of aggression.

Emotions

Emotions play a crucial role in making human social living possible. Innate emotions, like fear of snakes and strangers, universal facial expressions, and the evolutionary origins of events that trigger emotions (e.g., loss of social status, sexual rejection, death of a child) are all significant.

Charles Darwin emphasized the importance of communication of emotions between people and animals in his work "The Expressions of Emotions in Men and Animals" (1872). This communication facilitates social life by enabling us to adjust our behaviors.

Altruism

Altruism includes:

  • Inclusive fitness: Evolution favors genes that increase the survival of both the individual and their relatives. Examples include parental investment and investment toward relatives.

  • Kin altruism: Saving genes identical to one's own through helping relatives.

  • Reciprocal altruism: Helping non-relatives with the expectation of returned help.

Individuals who receive help but do not reciprocate are considered "cheaters." Society often shows scorn for free riders and honors heroes, indicating that our brains are prewired to understand the social nuances of cooperation and competition.

Altruism often stems from empathy rather than rational calculation. David Buss (1999) described evolved psychological mechanisms as specific psychological processes evolved to solve particular adaptive problems of survival or adaptation. Understanding cultural variations and specific behaviors is essential.

Evolved Psychological Mechanisms

These are specific psychological processes that have evolved because they solved particular adaptive problems.

Sexual Behavior

The primary goal is to pass on one's genes. Key aspects include:

  • Sexual attraction: Signals of fertility and health, attractiveness and facial symmetry, youth for women (indicating more reproductive years), hormone markers (estrogen in females, testosterone in males), low waist-to-hip ratio preference in men, and masculine bone structure preference in women.

  • Parental investment: Greater sexual selectivity by females.

  • Sexual opportunism: More common in males, but commitment to long-term relationships is also present to ensure offspring survival.

  • Paternal uncertainty: The extent of infidelity is not so different between genders; however, males face paternal uncertainty.

  • Sexual strategies: Short-term (male status and dominance) vs. long-term relationships (loyalty).

  • Income (men) and youth (women) predict mate retention.

In cultures with equal gender status, these preferences are reduced.

Early Attachment

Secure vs. insecure attachment styles, oxytocin, and the "friend and befriend" response to stress in females have evolutionary value for children.

Homosexuality

May involve component genes of empathy, sensitivity, and cooperation.

Parental Behavior

Nurturance increases the survival of one's genes. Stepchildren may face abuse or neglect and receive less financial support, indicating favoritism toward biological offspring. Human infants are born immature due to brain enlargement, leading to dependency that provides a learning opportunity.

Aggression and Dominance

Functions include:

  • Coopting resources of others.

  • Defending against attack.

  • Inflicting costs on same-sex rivals.

  • Negotiating status and power.

  • Deterring rivals.

  • Deterring mates from infidelity.

  • Reducing resources spent on genetically unrelated children.

Male competition for mates is influenced by testosterone. Alcoholism and antisocial disorder are related. Recent research emphasizes concern for status and respect among men and the need for dominance and respect within a group.

Culture

Humans are predisposed for culture through evolution. This includes language, symbols, tools and technology, and social organization. Cultural evolution involves evolutionary selective pressures, such as the taboo against eating beef in cultures needing those animals for plowing.

Language and Thought

Language provides humans with the capacity for consciousness and allows them to share information (e.g., about successful hunting). The "theory of mind" involves understanding the thoughts and intentions of others, relying on a distinct brain mechanism separate from general intelligence. Autism affects this ability. Symbolic thought, including rudimentary symbols like numbers, is present. The Framing Effect and automatic processing (Stroop test) also play roles.

Framing Effect

In the Asian disease problem proposed by Tversky & Kahneman (1981), decision-makers faced two frames. In the first frame:

  • Program A: Saving 200 people.

  • Program B: 1/3 probability of saving 600 people and 2/3 probability of saving no one.

72% preferred A. In the second frame:

  • Program C: 400 people will die.

  • Program D: 1/3 probability that nobody will die and 2/3 probability that 600 people will die.

22% preferred C. However, when the group size increased from 6 to 60, the framing effect diminished.

Genetics and Personality

  • Heritability: This statistic shows the proportion of variability of a trait in a population associated with genetic variability.

    • High heritability exists for happiness, coping styles, and likelihood of divorce

  • Emergenic traits: Phenotypic traits caused by a constellation of many genes that may not appear to run in families. Genes are not always active.

Temperament

The biologically based foundation of personality is based on a child's inherited predisposition. Examples include easy babies (happy, interactive) and difficult children (anxious, irritable). The EASI model includes:

  • Emotionality

  • Activity

  • Sociability

  • Impulsivity

The Big Five personality traits are:

  • Openness

  • Conscientiousness

  • Extraversion

  • Agreeableness

  • Neuroticism

Kagan's Model

Focuses on inhibited and uninhibited temperament.

Amygdala

Plays a role in temperament.

  • Genotype: The inherited genetic profile.

  • Phenotype: The observed characteristics based on both genetic and environmental influences.

Temperament and environmental effects are interdependent (e.g., how parents behave toward an inhibited child).

Biological Contributors to Personality

Critical areas include:

  • The Brain

  • Emotional Arousal

  • Cortical Arousal

The Brain

Composed of modules with specialized functions, such as recognizing faces and understanding facial expressions. Social judgments are associated with different lobes. Emotions, such as depression, anxiety, and fear, are linked to the right lobe. Neurotransmitters consist of over 150 different chemicals.

Emotional Arousal

Emotional intelligence is crucial. Antisocial personality disorder is associated with lower emotional arousal, empathy, less response to stress, and lower levels of serotonin. The left cerebral hemisphere is linked to approach and anger, while the right cerebral hemisphere is linked to avoidance. Emotional arousal is stable over time.

Cortical Arousal

Arousal of the brain's cortex, studied by Pavlov in dogs. The strong nervous system leads to increased strength of conditioning due to decreased inhibitory processes, while the weak nervous system shows inhibition to strong stimuli. Arousal is related to sensation-seeking: the seeking of varied, novel, complex, and intense sensations and experiences, and the willingness to take risks for such experiences.

Biological Factor Theories: Eysenck, Gray, and Others

  • Eysenck’s "PEN" Biological Model

  • Gray’s Reinforcement Sensitivity Theory

  • Cloninger’s Tridimensional Model

Eysenck’s “PEN” Biological Model

Three factors:

  • Extraversion

  • Neuroticism

  • Psychoticism

Extraversion

Individuals have "a strong nervous system" and differ biologically in neural dampening of incoming stimuli and dopamine system activity. Characteristics: sociable, lively, active, assertive, sensation-seeking, carefree, dominant, surgent, venturesome.

Neuroticism

Greater activity in the limbic system and higher emotional arousal. Characteristics: anxious, depressed, guilt feelings, low self-esteem, tense, irrational, shy, moody, emotional.

Psychoticism

A tendency to nonconformity or social deviance. Creative people may also score high. Physiological responses show quicker desensitization to violence and less likelihood of forming conditioned responses to punishment. Characteristics: aggressive, cold, egocentric, impersonal, impulsive, antisocial, unempathic, creative, tough-minded.

Gray’s Reinforcement Sensitivity Theory

  • Behavioral Activation System (BAS): Linked to reward and pleasure, causing approach behavior. Associated with dopamine dysregulation in bipolar disorder. High BAS scores indicate alcoholism, while low BAS sensitivity indicates depression. Approach behaviors include extraversion, sexual behavior, and aggression.

  • Behavioral Inhibition System (BIS): Sensitivity to punishment, fear, and aversive stimuli, leading to inhibited behavior. Associated with norepinephrine. Underactivation of BIS is linked to ADHD, impulsivity, and criminal behavior, while excessive activation is linked to anxiety disorders.

Activation of BAS and BIS guides learning by teaching what to approach and what to avoid.

Cloninger’s Tridimensional Model

  • Novelty seeking: Linked to low dopamine levels.

  • Harm avoidance: Linked to high serotonin levels.

  • Reward dependence: Linked to low norepinephrine levels.

Biological Mechanisms in Context

Biology may not always be the appropriate level of explanation for understanding phenomena. Experience can change biology (e.g., maternal deprivation affects the dopamine system). The effect of biology depends on the environment (e.g., shyness differs in China vs. the U.S.). Epigenetics demonstrates how environment can alter gene expression.