Biology and Behavior



1. Contrast, using examples, inherited behavior patterns with learned behavior patterns.

Inherited behaviors patterns are ones that, appear at a specific developmental stage, are observed in individuals raised in isolation, and are conducted entirely without practice (Sucking thumb). Learned behavior patterns are slowly developed (acquired) by observing others and are in response to experience. Adaptation occurs to the environment which includes the people with whom an individual interacts (reading).

2. Summarize the evidence supporting genetic influences on personality.

From twin studies genetic influence is in the range of 40 to 50%, and heritability is approximately the same for different traits.

Studies of twins suggest that the tendency to develop an extreme fear response is partly inherited, partly learned, and partly conditioned. That is, there is a genetic predisposition to fear for stimuli that are dangerous but fear can also be learned through conditioning and socialization (e.g. seeing a caregiver's reaction to a fear stimulus and modeling after them). As adults, formerly fearful children are at risk for anxiety disorders.

3. Discuss the genetic and environmental contributions to the development of fear. Differentiate between normal and extreme fear.

Fear is an emotion related to a specific, definite threat. The individual who is fearful acts in ways to protect him/herself. Fear behaviors are adaptive and essential for survival. Primitive fear behaviors are fight/flight/freeze. Infants have nonselective fear responses to noises, bright lights, and sudden movements. Studies of twins suggest that the tendency to develop an extreme fear response is partially inherited. Part is learned and part is conditioned. As adults, formerly fearful children are at risk for anxiety disorders.

4. Explain the relationship between facial expression, physiological responses and mood in fearful situations.

Facial muscle activity serves a display function in social interactions, communicating information about emotional state. The facial expressions associated with fear and happiness are easily recognizable across diverse cultures. Imagining unpleasant or frightening scenes increases tension in the muscles responsible for frowning or knitting the brows (corrugator muscles). Imagining pleasant scenes or thoughts increases tension in the cheek area responsible for smiles (zygomatic muscles).

5. Discuss the characteristics and mechanisms underlying psychogenic illness.

Fear produces physical symptoms unsubstantiated by physical findings or environmental cause. Common symptoms are headaches, dizziness, nausea, weakness. Symptoms can be experienced by a group of people who develop very similar fears, behaviors and physiological responses. Proposed mechanisms are observation, suggestion, and impaired processing of sensory stimuli.

6. Review the methods used in genetic investigation of the major mental illnesses, and the types of information that can be obtained.

Pedigree studies use a family tree to show the occurrence of diseases within a family. Family risk studies compare how frequently a disease occurs in the first degree relatives of the proband (affected individual) with how frequently it occurs in the general population. Twin studies assess the degree to which both members of a pair of twins manifest a given trait or disease. If both twins have a certain trait, they are said to be concordant for that trait. If only one twin of the pair has the trait, the pair is discordant. Adoption studies distinguish the effects of genetic factors from environmental factors in disease. If a condition has a genetic basis, the prevalence of the condition should be significantly greater among biologic relatives than among adoptive relatives. Cross fostering studies involve children born to normal biologic parents and adopted by affected parents. The rate of illness in these children is compared to the rate in children born to normal biologic parents and adopted by normal parents, and to the rate in children born to affected biologic parents and reared by normal parents

7. Discuss the genetic origins of schizophrenia, mood disorder, and alcoholism.

The risk of developing schizophrenia depends on your relation to an afflicted individual with the greatest likelihood being a monozygotic twin of an affected person, followed by children who have two affected parents, children who have one affected parent, and sibling of an affected person. A study of depressed probands showed a concordance of 40% in MZ twins and 17% in DZ. The incidence of bipolar illness is lower than that of unipolar, but the concordance rate for bipolar disorder is higher than that for unipolar disorder with MZ twins 62% and DZ twins 8%. Abusers’ siblings have a 5-8 fold greater risk than the general population (family studies). Adoptees with abuser biological parents are more likely to become abusers (adoption studies).
MZ twins are concordant for abuse (twin studies). Alcoholism is four times more prevalent in children of alcoholics than in children of non-alcoholics, even when these children are raised by adoptive parents.

8. Discuss the concept of addiction vulnerability and the evidence that supports the concept.

Having a genetic predisposition to addiction, alcoholism in the family, makes one more likely to become addicted than a person with no family history. (see above)

9. Describe the interaction between genetics and environment in the development of mental illness. Explain the results of the study by Caspi et al, 2003.

Study of serotonin transporter short and long alleles in children who suffered childhood abuse. Subjects with at least one short allele were more likely to become depressed after abuse and predicted thoughts of suicide after stressful situation. Those with the long allele were less prone to depression.

10. Discuss the implications of shared and non-shared environment on risk of psychiatric illness.

Shared (common) environment: Social class, Neighborhood, Maternal depression. Non-shared (unique) environment: Differential parenting, Life experiences of each child. 60% of the variance in adolescent antisocial behavior and 37% of the variance in depressive symptoms can be explained by negative parental behavior directed at the adolescent. Refers to the protective effects of harsh parental behavior on the sibling of the adolescent who is treated harshly. This sibling shows less psychopathology than expected.