Behaviour Flashcards

§ A reaction to stimuli § Human behavior is similar to animal behavior but is more variable § Behavioral genetics- study of the influence of genes on behavior o Which is more important: genetics or environment?

§ Brain chemicals or neurotransmitters can change our moods and actions § Released during neurotransmission when certain nerve cells in the brain become active § The speed or frequency of neurotransmission can alter how we react in a certain situation § A neurotransmitter is released to jump across the synapse (gap between nerve cells) § Endorphins- rush of exhilaration caused by exercise, stress, excitement

§ Chromosomal abnormalities, single gene defects, multigenic conditions can alter our behavior § Ex of a single gene defect = Huntington Disease (HD) o Symptoms = involuntary movements, personality changes o Mutant gene produces an altered version of the protein Huntington that breaks apart and accumulates in the brain cells o Cells w/ accumulations of Huntington die & as more cells die, behavioral changes appear § Fragile X syndrome- mutation in a specific region of X chromosome that causes behavioral changes o Causes autistic type behaviors and problems with aggression § Schizophrenia- multifactorial condition, collection of mental disorders o Hallucinations, delusions, disordered thinking, changed behavior

§ Behavioral geneticists, psychologists, psychiatrists study genetic influences on human behaviors § Identical twins have identical genomes and each has a set of genes that are exactly the same as that of their twin o If a trait or behavior is the same in identical twins, it has a genetic component o If two twins are raised in dif. environments & have dif behavioral traits, traits have a environmental component § Concordance- calculating how often a trait occurs in both members of a pair of twins o Identical twins are genetically identical; any genetic mutation carried by one is carried by the other & if this is true, the concordance rate is 1.0 o The concordance for a trait helps establish whether or not it has a genetic basis § Fraternal twins do not have identical DNA; share half their genes § Animal studies are another way scientists study behavior o If a gene is suspected to be involved in behavior, researches use recombinant DNA to insert a human gene, mutate mouse gene, change its pattern of expression and study the effects on the behavior of these genetically modified mice and offspring

§ Genetic causes of sexual orientation have been studied using combined methods that include twin studies, chromosomal analysis, pedigree analysis § There is a strong genetic component to homosexual behavior

§ The gene of aggressive and violent is an X linked trait and encodes for monoamine oxidase type A (MAOA) that breaks down neurotransmitters in the brain o When mutated, causes a condition called MAOA deficiency o Failure to break down neurotransmitters disrupts normal transmission of impulses o Changes normal functions in the nervous system and causes abnormal behavior

§ Behavioral genetics is a science in infancy; experts do not agree on findings and individual courts cannot decide how to use it to determine guilt or innocence § If we determine that genes cause someone to commit a crime, motive would not be relevant § Generally, XYY males are taller, more aggressive; does not mean they are criminals § Can a person be rehabilitated after committing a crime? o Rehab is the basis of our penal system o To change behavior, it is necessary to control behavior o How can someone w/ a genetic behavioral disorder control or change his/her behavior? § If a person could be proven to be insane, would this make him her not responsible? § In general, courts have held that only if a defendant cannot tell right from wrong and has a definite diagnosis of a medical condition, he/she is not guilty by reason of insanity