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The Nature and Nurture of Behavior

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1 The Nature and Nurture of Behavior
Even monkeys fall out of trees. Japanese Proverb The curious paradox is that when I accept myself just as I am, then I can change. Carl Rogers We are now going to venture into one the longest and most debated conflicts in psychology – what controls behavior? Is it our genes or is it our environment? Throughout our discussion, we’ll examine both viewpoints and the current beliefs in this argument.

2 Let’s start with genetics . . .
A stretch of DNA that produces a specific protein, which in turn forms building blocks of our bodies or drives the processes that allow us to live DNA (deoxyribonucleic acid): molecule that contains genes Human instruction manual: genes affect physical features, such as eye color and height, and behavior Dogs are bred for genetic disposition/behavior One gene in fruit flies can be altered to produce courtship behavior between two males

3 Darwin’s Natural Selection
Key is genetic fit with environment Mutation Depending on environment, genetic makeup or organisms evolves throughout generations of offspring, producing changes in the dominant physical features and behavior of a group of organisms Characteristics of organisms are molded to the requirements for survival in that particular environment. ‘Survival’ genes will come to be widespread in a population because those with these genes are the ones that live long enough to have many offspring. In turn, those offspring, equipped with the favorable characteristics inherited from their parents, will survive to have more offspring. And thus, the cycle continues.

4 Evolutionary Psychology
Using principles of natural selection, focuses on the evolution of behavior and the mind Mating behaviors One of the most studied areas in evolutionary psychology Why do we find certain characteristics attractive in a potential mate? From Darwin’s theories of natural selection, a branch of psychology has developed that we call evolutionary psychology. This sub-field focuses on the study of the evolution of behavior and the mind.

5 Evolutionary Psychology – Gender Differences in Attraction
Women prefer economic resources & older partners Men prefer physical attractiveness & younger partners These differences may arise from the different social roles the genders have historically held or because of evolutionary factors These differences are more typically seen in cultures with gender inequalities Men also report being more willing to have more sexual partners than women are. However, in the end, men and women are more similar than they are different. Most people (men and women) report that they want a single, long-term partner – even if they don’t want that now but will want that in the future. It’s also important to remember that these are just trends – it doesn’t mean that we will ALWAYS follow these patterns, its just that we are more likely to follow these patterns than not.

6 Criticisms of Evolutionary Explanations
Evolutionary theories are circular and sometimes untestable Alternate explanation Overall, women have fewer resources (Ganestead, 1993) Criticisms of the theory are that some aspects of it are untestable; that it is an oversimplification (particularly with regard to gender differences in the preference for physical attractiveness). Data on gender differences in the importance of physical attractiveness and of economic resources provide only mixed support. Finally, some researchers believe that findings can be explained by the fact that around the world, women have fewer resources than men do. In support of this latter interpretation, Gangestead (1993) found an association between women’s economic resources and their preference for a physically attractive man.

7 Behavioral Genetics How much of the differences among people are due to their genes and how much are due to the environment? Genes cannot be described in isolation: they can only be characterized in relation to the environments in which they operate We’ve been talking all throughout this course about this question: how much do genes affect behavior/mental processes compared to environmental influences? To better examine this question, we turn to a very unique research method – that of twin studies.

8 Twin studies Identical twins Fraternal twins Adoption studies
Zygote splits (monozygotic) Fraternal twins Two separate zygotes (dizygotic) Adoption studies Compared adopted kids with biological and adopted parents How do we effectively study whether the differences in mental processes/behavior are genetic? Twin studies are a good way to gain heritability estimates for mental processes and behavior. One method is to compare identical twins (where the twins are from the same egg that has split, thus they have identical genes) to fraternal twins (where the twins are from different genes, and thus they only share half their genes – the same as any pair of brothers or sisters). If environment is same for both identical and fraternal twins, then you can estimate heritablility for mental processes & behavior. Another method is to compare children who have been adopted to examine whether they are more like their biological parents (which would support the nature hypothesis) or their adopted parents (which would support the nurture hypothesis). This is an even more powerful method of study when you can find identical twins who have been raised by different parents.

9 Temperament Studies Examining how emotionally excitable an infant is
‘Easy’ babies are cheerful, relaxed & predictable ‘Difficult’ babies are more irritable, intense & unpredictable Temperament is mostly stable and mostly based on heredity Earlier temperament predicts later temperament and behavior Identical twins have more similar temperaments than fraternal twins

10 Nature vs. nurture? The environment has very little effect on personality development But that doesn’t mean that your parents don’t effect you at all Their influence can be seen in your attitudes, values, manners, religion, and politics Most behaviors/traits are an interaction of your genes and the environment The striking finding across a number of studies is that with regards to personality development, environmental factors have almost no impact on one’s personality. I know, you’re thinking I’m crazy, but think about it…for those of you who have siblings, you were all raised in the same household and share ½ your genes…but aren’t their moments when you just can’t understand anything your brother/sister says or does? If environment had an impact, shouldn’t you be almost identical?? But instead, you may have different hobbies, prefer different sports, and have different senses of humor. Now, even though there are limits to the effects of environment on personality characteristics, the environment in which you grow up does have an effect on your attitude’s, values, manners, religion, and politics. Thus, parenting does matter, just not in all the ways that people typically think it does. In thinking about how we develop, think of it as an interaction. Both your genetic disposition and the surrounding environment influence the type of person that you become. I like to think of it as your genes laying a foundation for preferences that your environment then picks up on and stimulates.

11 Environmental Influence
Should we really blame the parents? NO in the environmental sense and YES in the genetic sense Experience and brain development Use it or lose it, especially early on Peer influence Parents are necessary for early childhood survival – peers are necessary for lifelong survival Peers are who we play with, work with, and eventually mate with The general public, if you ask them what psychotherapy or psychoanaylsis are – they’ll probably mention something about blaming your parents (especially your mom) for all your problems. For a number of years, it was assumed that the best way to explain why someone was engaging in deviant behavior or experiencing mental illness was to look at the environment in which they were raised. So should we always blame the parents when people aren’t perfect? What we’re finding is that, based on what we’ve learned so far regarding their influence on personality, the answer is NO in the environmental sense and YES in the genetic sense. Since most of your personality is determined by your genes, and you got all those from your parents, then yes, they did have some influence on who you are today. But very little (typically between 10 and 12%) of their influence is a function of the environment they created for you to grow up in. One very important factor in determining personality traits and abilities later in life is the amount of stimulation your brain receives early on in life. Experience helps develop neural connections, even if the information is eventually lost or forgotten. Having established neural pathways and connections early on in life allows their use later. Those pathways that have not been activated eventually die-off and are not accessible later. Another very important factor in how we develop is that of the influence of our peers. If you think about it, it makes sense that our peers would be as influential as they are. Parents are how we survive early childhood – they give us food, shelter, unconditional love, and, hopefully, a stimulating and enriching environment. But it is our peers that will determine our lifelong survival – they are who we will play with, work with, and eventually mate with. Thus, it is this group of individuals that will determine our survival to adulthood – and thus, our survival to be able to procreate (which is still what we are all still after).

12 Cultural Influence Culture
The behaviors, ideas, attitudes, and traditions shared by a large group of people Norms: the rules for accepted and expected behavior (based on group membership) Regardless of the cultural norms of a group, most are very successful at raising children One important consideration is that while there are significant cultural differences present, we are still more alike than we are different Norms: in some cultures, you all would be expected to stand at attention until I entered the room and dismissed you…United States Air Force Academy.

13 Gender – Biologically Speaking
Until the 7th week of pregnancy, all babies are female It’s the activation of testosterone in a fetus that has the XY pair of chromosomes that triggers male organ production In the fourth & fifth months, different brain patterns develop due to different levels of testosterone and ovarian hormones

14 Gender – Socially Speaking
Gender roles The expectations about how men and women behave In nomadic cultures, there is minimal gender role occurrence Boys and girls experience the same upbringing In agricultural societies (of which ours originated), there are strict gender role structures in place Most of our gender identity is acquired through social learning

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