W4L2 explaining human behavior

Question 1

What is nature and nuture

Answer 1

• Nature: behaviour is determined by genetics; environment has little influence
• Nurture: behaviour is determined by learning from the environment and genetics has little influence

Question 2

The Seville Statement on Violence (UNESCO, 1989), refutes “the notion that organized human violence is biologically determined

Answer 2

1. It is scientifically incorrect to say that we have inherited a tendency to make war from our animal ancestors
2. It is scientifically incorrect to say that war or any other violent behaviour is genetically programmed into our human nature
3. It is scientifically incorrect to say that in the course of evolution there has been a selection for aggressive behaviour more than for any other kinds of behaviour
4. It is scientifically incorrect to say that humans have a violent brain
5. It is scientifically incorrect to say that war is caused by instinct or any single motivation

Question 3

Nature and nuture characteristic

Answer 3

Some characteristics do have a genetic cause:
* cystic fibrosis: caused by a recessive gene located on chromosome 7
* red hair: caused by variants of the MC1R gene complex, located on chromosome 16
Some characteristics have an environmental cause:
* the acquisition of a particular language depends upon what is spoken in the child’s environment
Mostly they reflect both:
* the phenotype (or set of traits) produced by a gene(s) may depend upon the context in which the gene is expressed

Question 4

Cross-fostering experiments in animal

Answer 4

Offspring are randomly split between biological and ‘foster’ parents and differences in trait expression reveal the influence of ‘genetic’ and ‘environmental effects
-In rat, cross fostering does not have an effect on gene expression BUT embryo transfer can affect gene expression

Question 5

Distinguishing between genes &
environment Experiment in human

Answer 5

Adoption studies
* comparisons between offspring behavior and the characteristics of both the biological and adoptive parents
Twin studies
* classical twin studies compare data from identical/monozygotic (MZ) with fraternal/dizygotic (DZ) twin pairs, raised in the same circumstances

Question 6

Types of twins

Answer 6

Dizygotic Twins, separate amniotic sac
B. Dizygotic Twins, shared amniotic sac (rare)
C. Monozygotic Twins, share/ separate amniotic sac

Question 7

Heretibility study result

Answer 7

• identify if sleep pattern is genetic or not: no genetic correlation in school day but on free day, genetic is a stronger determinations factor (genetic can be overwritten)
  -study on drug dependent: show large variability between control. Cultural influences

Question 8

Methodological approaches to human studies

Answer 8

1. Construct an evolutionary explanation of a pattern human emotions: weak data to explore the evolution of disgust
2. Ask why a behaviour is maintained in the population, despite a fitness cost human handedness: what maintains a polymorphism with

Question 9

Study on human emotion: disgust and disease

Answer 9

Web-based survey (hosted by the BBC), completed by 77,000 people, but
exclusions yielded < 40,000 respondents
respondents asked to view photographs and rank them according to disgust (internet based)
respondents mostly from Europe (78%), with others from North America
and Canada (13%), Asia (5%), Oceania (2%), Africa (2%), South America (1%)

Question 10

Result of the disease and disgust study

Answer 10

• 98% of respondents found the disease-relevant pictures equally or more disgusting than their pairs
• no interaction between ranking and respondent’s location was reported (not surprising – why?)
• females (mean 3.5) rated disease-salient images significantly more disgusting than males (mean 3.2)
  -ranking of disgust decrease with age (historical difference)
  -large variation in disease-irrelevant images
  -little evidence that these respond have biological origin, more likely to be culture inspired

Question 11

Sharing toothbrush study

Answer 11

-more likely to share with people closer to us
Sharing a person’s bodily fluids becomes more disgusting as that person becomes
less familiar because strangers are more likely to carry novel pathogens and
hence present a greater disease threat to a naive immune system

Question 12

Basic on lefthandness

Answer 12

• left-handed people in the minority in all human populations
• several alleged fitness costs associated with left-handedness
• countervailing benefit must exist to maintain polymorphism

Question 13

left handiness gene association

Answer 13

Sample of 30,161 subjects aged 18–69 from a questionnaire survey of the older
Finnish Twin Cohort
Environmental effects account for most observed variance in handedness, but estimates of familial effects increased if forced handedness was taken into account
-MZ have higher percentage than DZ

Question 14

Cost of left handedness

Answer 14

• eight hand have longer life expectancy
  -but cost occur post-reproduction age so unlikely to be a strong selection pressure

Question 15

Left handiness benefit

Answer 15

left-handed people have an advantage in sports involving dual confrontations (fencing, tennis, baseball)
* if left-handed people have similar advantage in aggressive interactions, then left-handedness predicted to be more prevalent in more violent societies

Question 16

Problem with lefhandness benefit

Answer 16

is the cost of left-handedness substantial, and relevant to the societies in this study?
* is homicide rate the best estimate of prevalence of one-to-one fights?
* is the correlation confounded (e.g., differences in rates of handedness and violence between field and literature studies)