5 Nature And Nurture

Nature and Nurture

Chapter 3 99-133

Nature vs. Nurture 

One of the most important questions in psychology is: How much of human behavior is caused by our physical make up, our genes (nature) vs. how much is what we learn by experience in our environment (nurture).

How much of your personality is from your parents genetics And how much did you just learn From living your life?

Genes: Our Biological Blueprint 





Inside the nucleus of every cell are 46 Chromosomes (originally 23 from the mother, 23 from the father). Chromosomes contain Genes. Genes are segments of DNA that code for making a particular protein. The proteins that are made become how you are physically built.

The Human Genome  The

human genome is a complete set of instructions for making a human.  The human genome has 3 billion bonded pairs of nucleotides organized as DNA sequences. They are being mapped out so that doctors will know what each one does.

The Human Genome Project 



This Human Genome Project has the potential to save more lives than any other technology, it also raises serious ethical questions regarding cloning and human engineering. Human traits are influenced by gene complexes – many genes working together. There is no “angry” gene, but a number of genes working together could make someone’s personality more aggressive. This type of study is called molecular genetics.

Evolutionary Psychology 



Natural Selection - The theory that organisms with the genetic trait variations are more likely to reproduce and survive. For example people are predisposed to enjoy sweets and fats because our ancestors knew that food would help them survive famines… however, now this trait can be a cause of obesity in a world where food is plentiful, perhaps in a million years there will be people who are mostly predisposed to eat less?

Gender  In

general men are more likely to initiate sexual activity regardless of culture or where you live.  Men are more attracted to youthful, healthy looking, females who waists are a third narrower than the hips (a sign of many child bearing years to come).  Woman are attracted to healthy looking, mature, dominant, bold and affluent men – traits that denote the ability to support and protect.

The most important human trait  The

most important human trait however, is our amazing ability to use our mind and reason to adapt to any situation and condition. This perhaps more than anything else has made humans a successful species as well as one that is very hard to predict and define.

Twin Studies  Behavior

genetics - The study of the relative power of genes or environment to influence behavior.  Environment – every non genetic influence. Includes prenatal nutrition, post natal care, etc.  Psychologists have extensively used Twin Studies to study nature vs. nurture.

Twin Studies 



Identical Twins – Twins who develop from a single fertilized egg that splits in two, creating two genetically identical people. Fraternal Twins – Twins who develop from two separate eggs and sperm. Genetically they are no closer than normal sisters or brothers but they do share a fetal environment.

Identical vs. Fraternal

Identical Twins developed from the same egg and sperm

Fraternal twins from a racially mixed marriage. They come from two separate eggs and sperm coming together.

Separated Twins/Adoptive Studies  By

studying separated twins and adoptive children who don’t grow up with their parents we can learn even more about how heredity and environment affect behavior.  For example will adoptive children have temperaments (how a person emotionally reacts to things) closer to their birth parents or to their adoptive parents?

Development video

 http://www.learner.org/resources/series138.html?p  Heritability

– the proportion of variation among individuals that we can attribute to genes. This does NOT apply to individual circumstance but only measurements among people as a whole.

Gene-Environment Interaction  Gene’s

and the environment both influence us but its more complicated than that because they also continuously influence each other.  For example, a baby with a predisposition to smile a lot not only inherited that trait, but because people will want to play with that baby more they will also be influenced by their environment!

Infant Development  Prenatal

environment is very important for infant development, even placenta placement can affect twins and cause one to thrive more than the other.  Experience causes brain development. Up to 20% more neural synapses have been recorded in rats that have “enriched” environments to develop in. Attention is needed for the brain to develop. Some animals who receive no attention after birth even if they are fed regularly will die.

Other Environment Influences  Peers

– Children often listen to their peers more than their parents. Teens almost always do  Culture – People self enforce culture norms such as personal space. Meme’s are used to describe the creation of cultural ideas that are passed on.  Culture also affects child rearing promoting independent ideals or teaching loyalty to the group

Gender – Nature or Nurture?  The

physical characteristics of male and female are obviously affected by nature. However, research shows that mental dispositions can be affected as well by genetic control of hormones.  Nurture controls gender roles or what society expects a certain gender to do.

Social Learning Theory  Theory

that we learn social behavior by observing and imitating what we see being rewarded and punished.