FINAL PAPER 1 STUDIES (Bio Specialization + HL Topic)

To see if learning a new skill would have an effect on the brains of participants (in this case juggling)

• 24 volunteers between the age of 20-24

• 20 females and 4 males

• All participants were non jugglers at the start of the study

• Each participants had an MRI scan at the start of the study to serve as a base rate for grey matter and brain structure

The participants were separated into two conditions (the jugglers and non jugglers)

Those that were in the juggling condition were taught a three ball cascade juggling routine

They were asked to practice the routine and notify the researchers when they have mastered the skill at that point the researchers conducted a second MRI scan on the jugglers

After the second MRI scan the researchers told the participants to stop practicing the juggling routine

After three months a final third MRI scan was conducted on participants in the juggling condition

The non juggler condition served as a control group for the duration of the study

To analyze the MRI scans, researchers used a voxel-based morphometry (VBM) to determine any significant differences in neural density (grey matter) in the brains of non-jugglers and jugglers

From the baseline scans at the start of the study there were no significant regional differences in grey matter between the two conditions

However, at the end of the first part of the study, jugglers showed a significantly larger amount of grey matter in the mid-temporal area in both hemispheres - an area associated with visual memory -

Three months after the jugglers stop juggling, MRI scans showed that the amount of grey matter in the mid-temporal area in both hemispheres had decreased

There was no change in the non juggler condition for the duration of the study

Strengths

• There was a pre-test, post-test design to show the differences in neural density over time

• The study was a lab experiment, providing a cause and effect relationship

• There was a control group (the non jugglers) that served as a control group (help ensure the internal validity)

Limitations

• The sample size was very small (data may not be reliable) The study has potential problems with internal validity as the participants were in their home environments for the majority of the study

• The study will need to be replicated to establish its reliability

To investigate whether changes could be detected in the brains of London taxi drivers and to further investigate the role of the hippocampus in spatial memory.

• 16 right handed male taxi drivers

• 50 right handed males who did not drive taxis

The participants must have had completed the "knowledge" test and held their license for at least 1.5 years

There was a variety of ages to show that age is not a confounding variable

The data from the MRI was measured using two different techniques: voxel-based morphometry (VBM) and pixel counting

• Voxel-based morphometry (VBM) was used in this study to measure the density of grey matter in the brain.

• Pixel counting consists of counting the pixels in the images provided by the MRI scans in order to calculate the area of the hippocampus.

Single-blinded study - researchers looked at MRI scans of both the participants and control group without knowing which belonged to what group.

MRI scans were used to observe the structure of the hippocampus.

There were two key findings of the study:

First, pixel counting revealed that the posterior hippocampi of taxi drivers were significantly larger relative to those of control subjects and the anterior hippocampus were significantly smaller.

VBM showed that the volume of the right posterior hippocampus correlated with the amount of time spent as a taxi driver.

No differences were observed in other parts of the brain.

Maguire argues that this demonstrates that the hippocampus may change in response to environmental demands, as it appears that the posterior hippocampus is involved when previously learned spatial information is used, whereas the anterior hippocampal region may be more involved during the encoding of new environmental layouts.

Strengths

• The brain scans were coded so that analysis could be done blindly - that is, the researchers did not know which brain scan belonged to which participant in order to avoid researcher bias.

• You cannot argue that the MRI has low ecological validity because the participants were not asked to do anything while in the scanner. They simply had their brain anatomy measured.

• The study is ethically sound as the MRI does not pose any health risks to the participants and all gave consent.

Limitations

• Quasi-experiment = no manipulation of the IV (spatial memory), therefore, a cause and effect relationship cannot be established.

• Although the study appears to have sampling bias, it is a reality that the vast majority of London cabbies (Taxi Drivers) are male. However, it still does make it difficult to generalize the findings

to investigate neural mechanisms associated with the attraction system

• Lab experiment

• 10 women and 7 men between 18-26 years of age who were in love

To determine duration, intensity and nature of the participant's romantic love, the researcher interviewed participants and asked them to complete questionnaire: "Passionate Love Scale (PLS)"

They were placed in fMRI scanner, showed picture of beloved, then asked to count backwards, then show picture of acquaintance. Repeat 6 times

fMRI results showed different parts of the brain were activated when participants viewed photos of beloveds vs. acquaintances. When showed picture of beloved, the right ventral tegmental area (VTA) activated. This is dopamine rich area of brain and part of the brain's reward system.

The results indicate the possibility of brain circuits dedicated to attraction are same circuits associated with addiction. Dopamine increases with anticipation of reward (not just getting a reward). We anticipate reward so our brains are wired to drive us towards attaining those rewards. This is evolutionary explanations of human behavior; if we don't reproduce, our genes won't be passed on

Strengths

• This is a highly controlled clinical method of obtaining data and Fisher and her colleagues checked objectivity at every stage of the procedure.

• Identification of the reward center of the brain support to the idea that human beings may have an evolved brain system which ensures that they become ‘hooked’ on an individual, which increases the possibility of them reproducing.

• The standardized procedure means that the study is replicable, which increases its reliability.

Limitations

• The small sample size of 17 participants means that the results are not very meaningful and may not be robust in terms of statistical analysis.

• The sample comprised relatively young students from the same university, which also limits generalizability.

• Additionally, it is overly reductionist to use brain scans to determine how romantic love is experienced: there may be a range of other factors involved, such as similarity, same upbringing, shared ideals, cultural influences. So little is really known about the brain that there may be other explanations for the activation of the reward centers during the fMRI scan – perhaps the participants were simply excited to be in a brain scanner for the first time and this stimulated the dopamine-rich areas.

• Scanning participants’ brains is clearly an artificial task, which means that the results are low in ecological validity.

• Use of fMRI scans is also an expensive way to collect data, which is possibly why the sample is so small.

To investigate the effects of serotonin on prosocial behavior

• Lab Experiment

• 30 healthy participants (~15 males and females, 25 years old) were tested for any mental or physical health problems before being selected for the experiment.

In the experimental group, participants were given a dose of citalopram, an SSRI.

In the control group, participants were given a placebo.

After taking the drug, participants were given a series of moral dilemmas (the personal or impersonal trolley problem), which made them choose between a utilitarian outcome (saving 5 people) and aversive harmful actions (letting 1 person be killed)

Responses to the impersonal version were unaffected by citalopram.

Participants with SSRIs in the personal scenario were much less likely to push the man off the bridge than participants in the placebo conditions.

Serotonin reduces the acceptability of personal harm and therefore promotes prosocial behavior (behavior intended to help others)

Strengths

• Double-blind design

• Repeated measures design (comparing one to themself)

• Construct validity (operationalized well, although they didn't measure serotonin)

Limitations

• No brain scan to show that the brain was actually active, so can't really show cause and effect

• Low population validity and volunteer sampling

• Healthy adults shouldn't be taking SSRIs

• Low ecological validity as trolley problems are not real, also in a lab

• Testing effect, repeated measures

• History bias

To investigate the role of adrenaline and the amygdala in the creation of emotional memories.

Participants were divided into two groups. Each group saw 12 slides which were accompanied by a very different story.

In the first condition, the participant heard a rather boring story about a woman and her son who paid a visit to the son’s father in a hospital where they witnessed the staff in a disaster preparation drill of a simulated accident victim.

In the second condition, the participant heard a story where the boy was involved in a car accident where his feet were severed. He was quickly brought to the hospital where the surgeons reattached the injured limbs. Then he stayed in the hospital for some weeks and went home with his mother.

After viewing the slides, the participants were asked how emotional they found the story on a scale of 1 - 10.

Two weeks after participating in the experiment the participants were asked to come back and their memory for specific details of the story were tested.

The test was a recognition task that consisted of a series of questions about the slides with three options for them to choose from.

The researchers then did a follow-up study. The above procedure was repeated, but this time the participants in the "traumatic story" condition were injected with either a beta-blocker called propranolol or a placebo. Beta-blockers are used to slow down heart rates. It was used in the study since it prevents the activation of the amygdala.

In the original version of the experiment, the researchers found that the participants who had heard the more emotionally arousing story demonstrated better recall of specific details of the story. They could also recall more details from the slides.

In the follow-up study, they found that those that had received the beta-blocker did no better than the group that had heard the "mundane" story. They, therefore, concluded that the amygdala plays a significant role in the creation of memories linked to emotional arousal.

Strengths

• The fact that the researchers could block adrenaline in an experimental design gives rise to a cause-and-effect relationship between adrenaline and activation of the amygdala to create emotional significance of the story.

• The study can be easily replicated because of its standardized procedure, allowing other researchers to test the reliability of the results.

Limitations

• The study is artificial in nature and highly controlled. Therefore, there is a concern about ecological validity.

• As the recognition task only had three options, it is possible that this is not a valid test of memory.

To investigate whether high levels of the stress hormone cortisol interfere with verbal declarative memory.

• Lab experiment

• All participants were employees or students in university

• All participants were given a clinical interview with a physician. They were excluded from the sample if they had any medical issues that could alter their hormonal levels, especially cortisol, such as pregnancy or mental illness.

The researchers carried out a double blind laboratory experiment in which the participants were matched for age and gender to one of three conditions:

Condition 1 – High level of cortisol: The participants in the high-level cortisol group were given a tablet containing 160 mg of cortisol on each day of the four-day experiment. This dose of cortisol produces blood levels similar to those seen in people experiencing a major stress event.

Condition 2 – Low level of cortisol: The participants in the low level of cortisol group were given a tablet containing 40 mg of cortisol per day. This dose is similar to the amount of cortisol circulating in the bloodstream of people undergoing minor surgical procedures such as having stitches removed.

Condition 3 – Placebo group: The participants in this condition were given placebo tablets - that is, a tablet that looked like the other tablets but with no active ingredient. This was done in order to have a control group.

All participants were asked to listen to and recall a prose paragraph. Each day they were given a different piece of prose with the same level of difficulty. They were tested three times.

The results indicated that high cortisol levels impaired performance in the memory task since the participants who received the highest level of cortisol also showed the worst performance in verbal declarative memory.

The researchers were also able to verify that the effect was not permanent; the performance of participants in the high cortisol condition returned to normal after they stopped taking the hormone tablet.

According to the researchers, these results demonstrate a clear link between levels of cortisol and remembering. It appears that high levels of cortisol interfered with the recall of the prose passage.

There was no statistical difference between the low dose and placebo groups on any day of testing and the researchers claimed that paragraph performance increased over time for the placebo and low dose groups because of practice effects or procedural learning

Strengths

• The researchers carried out a baseline test in order to eliminate the possible confounding variable of individual differences between groups.

• Manipulation of the IV (cortisol levels) and confounding variables show that the study is highly controlled, leading to high internal validity. This means that a cause and effect relationship can be established.

Limitations

• The experiment ran over several days and the participants were not in the lab the whole time, so the researchers did not have full control over extraneous variables - for example, individual stressors in the lives of the participants. In spite of this, there was a clear relationship between the amount of cortisol ingested and the performance on the memory test.

• Different texts were used for days 1 and 4. However, the researchers counterbalanced the use of the texts to act as a control that the difficulty of the text did not play a role in recall.

• Memorizing a piece of prose is perhaps not the most authentic memory experience. Although it may explain student exam stress, the ability to generalize the results to other situations may be limited.

• There are ethical considerations in the study. The participants ingested cortisol which affected their memory negatively. However, the participants had signed an informed consent form and the damage was not permanent.

To investigate the role of androstadienone and estratetraenol in conveying gender information

• Lab experiment

• 96 participants (24 heterosexual men, 24 heterosexual women, 24 gay men and 24 lesbian women)

Participants were asked to watch stick figures walking on a screen and to determine their gender. While carrying out the task, the participants were exposed to the smell of cloves.

1. In the first condition, the cloves were mixed with androstadienone.

2. In the second condition, the cloves were mixed with estratetraenol.

3. In the control condition, only cloves were used.

Smelling androstadienone biased heterosexual females and gay males, but not heterosexual males, toward perceiving the walkers as more masculine. By contrast, smelling estratetraenol biases heterosexual males and lesbian women toward perceiving the walkers as more feminine.

The researchers concluded that pheromones influence communication of gender information in a sex-specific manner.

Strengths

• Manipulation of the IV (androstadienone exposed) and confounding variables show that the study is highly controlled, leading to high internal validity. This means that a cause and effect relationship can be established.

Limitations

• Low reliability - Hare et al failed to replicate the study with a similar method and procedure.

• Low mundane realism - The dose of AND and EST used in this study was significantly higher than humans naturally secrete. This means that although Zhou's study determined a significant effect, it is unlikely that this represents actual human behavior.

To investigate the effect of androstadienone on the mood of women in the presence of men.

• 37 heterosexual women, mean age 25

• 2x2 experimental design (two independent variables with 2 levels each)

• Experimenter was either a female or male.

Female participants' mood was studied, and then assessed after being exposed to either androstadienone or control solution, and in the presence of either a male or a female experimenter.

The experimenter carried out a number of measurements including several questionnaires. One questionnaire measured mood.

Androstadienone increased women's mood in the  presence of a male experimenter, but not a female experimenter.

Androstadienone may serve the function of signaling sexual attractiveness, which supports its role as a pheromone.

Strengths

• Manipulation of the IV (pheromone exposed) and confounding variables show that the study is highly controlled, leading to high internal validity. This means that a cause and effect relationship can be established.

To determine whether there is evidence for a gene-environment interaction for a mutation of the serotonin transporter gene (5-HTT).

• Quasi-experiment

• ~850 New Zealand 26-year-olds.

• All had been assessed for mental health on an every-other-year basis until they were 21.

They were divided into three groups based on their 5-HTT alleles:

• Group 1: two short alleles

• Group 2: one short and one long allele

• Group 3: two long alleles.

The mutation of the 5-HTT gene has the shorter alleles.

The participants were asked to fill in a "Stressful life events" questionnaire which asked them about the frequency of 14 different events - including financial, employment, health, and relationship stressors - between the ages of 21 and 26. They were also assessed for depression.

• People who had inherited one or more short versions of the allele demonstrated more symptoms of depression and suicidal ideation in response to stressful life events. The effect was strongest for those with three or more stressful life events.

• Simply inheriting the gene was not enough to lead to depression, but the genes' interaction with stressful life events increased one's likelihood of developing depression.

Strengths

• Acknowledges the interaction between both biological and environmental factors in depression (gene-environment interaction). This is a more holistic approach, not reductionistic.

• High reliability - Longitudinal study, assessed from age 3

• Population validity (Generalizability) - High sample size

Limitations

• Correlational = no cause and effect relationship can be established

• Third variable problem - It may be the salience of the negative life events which plays a role in depression - that is, those that recalled them more easily may have a tendency towards depression. Those who are more resilient may not recall negative life events as easily.

• Risch et al. carried out a meta-analysis of attempted replications and found that the results were not able to be replicated (low reliability).

To investigate whether the MAOA gene predicts aggressive behavior when provoked.

• Lab quasi-experiment (participants were not randomly allocated to conditions thus not a true experiment)

• 78 male subjects (a mix of MAOA-H and MAOA-L) MAOA-L is the variant (hypothesize to be more aggressive)

Participants did a simulation in which they were asked to administer hot sauce to fictional opponents who they were told don't like hot sauce (this was the supposed aggressive behavior)

In each round they were told that their opponent had taken a portion of their earnings/money

They could then punish their opponent by administering hot sauce The money taken was 0%, then 20%, then 80% in each round (3 rounds)

Individuals with MAOA-L were significantly more likely to administer the hot sauce compared to MAOA-H when 80% of their earnings were taken

When it was only 20% taken the difference between MAOA-H and MAOA-L was minimal

Evidence of a gene-environment interaction Individuals with MAOA-L (genetic variation) are more likely to demonstrate aggressive behavior when provoked through the environment

Strengths

• Shows gene-environment interaction between aggression and being provoked

Limitations

• Quasi-experiment = no manipulation of the IV (genes), therefore, a cause and effect relationship cannot be established.

• Low mundane realism (generalizability). Giving someone really spicy hot sauce is not exactly the same as committing a violent crime against them in a real world setting.

• Low construct validity (internal validity). Is this really measuring aggressive behavior?

To study the role that genetics play in MDD

• Correlational study

• • Over 15 000 twins were found in Swedish twin registry

  • Telephone interviews were carried out assessing lifetime major depression by using modified DSM-IV criteria

  • Also asked questions about the twins' 'shared environment' (when they were living together) and 'individual specific environment' (personal life events that may make them more susceptible to depression)

In order to gather their data, the researchers used a team of trained interviewers to carry out telephone interviews. Interviews were carried out between 1998 and 2003.

The interviewers assessed lifetime major depression by using modified DSM-IV criteria. ~8000 twins met the criteria for a diagnosis of major depression at some point in their life - and ~300 twins voluntarily discussed a history of antidepressant treatment.

In addition to this information, the interviewers also asked questions about the twins "shared environment" - that is, when they were living in the same household - and their "individual-specific environment" - that is, adult personal life events that may make members of the twin pair more susceptible to depression.

The results indicate that the concordance rates for major depression were significantly higher in women than men. In addition, the correlations were significantly higher in monozygotic than in dizygotic twins. They also found no correlation between the number of years that the twins had lived together and lifetime major depression. The estimated heritability of major depression was 0.38, in line with previous research. There were also no significant differences seen in the roles of genetic and environmental factors in major depression in the three cohorts spanning birth years 1900-1958. Even when they split the entire cohort into pre and post World War II, there was no significant difference. This study suggests both that the heritability of major depression is higher in women than in men and that some genetic risk factors for major depression are sex-specific. In addition, the study confirms the level of heritability of major depression found in other studies, strengthening the reliability of European twin studies.

Strengths

• The study appears to confirm previous research, strengthening the reliability of the findings

• Very large sample size taken from a single population (~15,500)

Limitations

• Correlational = no manipulation of the IV (genes), therefore, a cause and effect relationship cannot be established.

• No particular genes were isolated and tested in the study

• Information about life-events and depressive symptoms was self-reported

• Making a clinical diagnosis by telephone may be considered of questionable validity

To study the potential genetic nature of Major Depressive Disorder.

• Longitudinal family study with a sample

• 161 grandchildren and their parents and grandparents

The study took place over a twenty year period, looking at families at high and low risk for depression.

The original sample of depressed patients (now, the grandparents) was selected from an outpatient clinic with a specialization in the treatment of mood disorders. The non-depressed participants were selected from the same local community. The original sample of parents and children were interviewed four times during this period. The children are now adults and have children of their own - allowing for study of the third generation.

Data was collected from clinicians, blind to past diagnosis of depression or to data collected in previous interviews. In order to establish credibility, data triangulation was used. Children were evaluated by two experienced clinicians - with one being a child psychiatrist and the other a psychologist. The inter-rater reliability of their diagnoses were 0.82 for MDD, 0.65 for anxiety disorders and 0.94 for alcohol dependency. The researchers found high rates of psychiatric disorders in the grandchildren with two generations of major depression.

By 12-years-old, 59.2% of the grandchildren were already showing signs of a psychiatric disorder - most commonly anxiety disorders. Children had an increased risk of any disorder if depression was observed in both the grandparents and the parents, compared to children where their parents were not depressed.

In addition, the severity of a parent's depression was correlated with an increased rate of a mood disorder in the children.

Strengths

• The study is longitudinal, increasing the reliability of the data.

• The use of researcher triangulation increases the credibility of the findings.

Limitations

• The amount of time that a child spent with a health grandparent may be a confounding variable in the study.

• Although family (kinship) studies indicate a potential genetic link to behavior, there is no actual genotype studied.

To investigate the evolutionary origin of the disgust reaction.

1. Disgust should be felt more strongly when faced with disease-salient stimulus as opposed to similar stimulus with less salience.

2. Disgust should operate in a similar way across cultures.

3. Disgust should be more pronounced in females since they have to protect their babies in addition to themselves.

4. Disgust should become weaker as the individuals reproductive potential declines with age.

5. Disgust should be stronger in contact with strangers than close relatives because strangers potentially carry novel pathogens.

A survey was placed on the BBC Science website.

~40,000 participants across 165 countries, all ages and both sexes.

Participants were asked a set of demographic questions regarding their age, sex, country, etc. They were then asked to rate 20 photographs for disgust on a scale of 1-5.

Of the 20 photographs, 7 pairs were paired for disease salience vs less disease salience.

Last question asked: "With whom would you like to share a toothbrush?" This was to test the 5th hypothesis.

Found that the disgust reaction was more strongly elicited for those images of the pairs that evoked a health threat. They also found that the disgust reaction also decreased with ages and was higher in women than men.

Strengths

• Applicable

• Generalizable

• Cost/time effective

Limitations

• Correlational

• No control over variables

• Online study

To determine whether one's MHC would affect mate choice

• 49 female and 44 male students from a Swiss university.

• Each participant was “typed” for their MHC, and a wide variance of MHC was included in the sample.

• It was noted if the women were taking oral contraceptives.

The men were asked to wear a T-shirt for two nights and to keep the T-shirt in an open plastic bag during the day. They were given perfume-free detergent to wash clothes, bed clothes, and perfume-free soap for showering. They were asked not to use any deodorants or perfumes, to refrain from smoking tobacco or drinking alcohol, to avoid all spicy foods and to not engage in any sexual activity.

Two days later, the women were asked to rank the smell of 7 t-shirts, each in a cardboard box with a “smelling hole.” They were also asked to use a nose spray for the 14 days before the experiment to regenerate the mucous membrane and prevent colds or flu.

3 of the 7 boxes contained T-shirts from men with MHC similar to the woman's own;

• 3 contained T-shirts from MHC dissimilar men

• 1 contained an unworn T-shirt as a control

Alone in a room, every woman scored the odors of the T-shirts for intensity (range 0-10) and for pleasantness and sexiness (range 0-10, 5 = neutral).

Women scored male body odors as more pleasant when they differed from their own MHC than when they were more similar. This difference in odor assessment was reversed when the women rating the odors were taking oral contraceptives.

MHC may influence mate choice, showing how we have evolved to detect MHC-dissimilar scents as more attractive to produce a healthier child.

Strengths

• Double-blind study, since neither the researcher nor the participant knew what shirt they were exposed to, reducing demand characteristics

• Met ethical standards as consent was obtained from all participants and they were debriefed

Limitations

• Reductionist – over-simplifies the behavior of human mate selection by bringing it down to the MHC, ignoring cognitive and socio-cultural factors

• Population validity – Participants were similar in age and culture (Swiss university students)

To determine the effect of stress hormones (glucocorticoids) on memory.

EMPHASIZE … FOR BRAIN & BEHAVIOR, STRESS HORMONES FOR HORMONES & BEHAVIOR, AND EPIGENETICS FOR GENES AND BEHAVIOR

• Lab experiment

• Independent samples design - the rats were randomly allocated to one of two conditions.

Newborn rats were handled daily by the researchers for three weeks - from the day of their birth until the day of weaning.

• During this time, the rats in the treatment group were taken away from their mothers for 15 minutes and placed in a plastic container lined with a paper towel. They were then brushed for an intense 15 minutes to simulate the grooming of the mother rat.

• The rats in the control group were taken away from their mother but there was no handling by the researchers.

To test the effect of these elevated rates of stress hormones over their lifetime, the two-year-old rats were put into a pool of milky water. In the pool was a platform.

The researchers tracked the route of the rats as they sought out the platform based on the rats' memories of previous attempts to escape the water.

BRAIN AND BEHAVIOR → Hippocampal cell loss and pronounced spatial memory deficits emerged with age in the neglected rats but were almost absent in the rats groomed by the researchers.

HORMONES AND BEHAVIOR → The researchers found that high levels of glucocorticoids - stress hormones - in the early life of a rat resulted in changes that affected the rats in old age.

GENES AND BEHAVIOR → It appears that the extra stroking that the rats received led to an activation of genes that are responsible for the reaction to the stress response (epigenetics).

BRAIN AND BEHAVIOR → Neglected rats have worse hippocampal cells and spatial memory than the nurtured ones. Relating to humans, this can mean that more nurturing behavior from parents can lead to a child with better spatial memory.

HORMONES AND BEHAVIOR → Those rats that are groomed, regulate stress better. This leads to lower lifetime cortisol levels which means that they have less memory impairment later in life.

GENES AND BEHAVIOR → This study is an example of epigenetics - the grooming process “turns on” the genes that help the young rat cope with stress - which then leads to a longer and healthier life.

This is a good example of an animal model used to study the effects of stress on humans. This is done not only because of the genetic similarities between mice and humans, but also because the shorter lifespan of rats that makes this study possible.

Strengths

• It is questionable to what extent we can generalize the findings from rats to human beings. However, there is research on humans that demonstrates similar results.

Limitations

• The study was artificial - lacking ecological validity as the rats were not in their natural environment.

• To measure hippocampal volume in rats, the animals had to be killed. There are ethical concerns about the killing of animals in research (RRR).

Investigate the effects of social hierarchy on the cortisol level of baboons

An observational, longitudinal (30 years), natural experiment of a group of baboons in Kenya

The group of baboons were assessed on their position in the social hierarchy of the group.

They were then chosen at random to have a sample of blood taken to assess their cortisol levels.

The study found that the baboons at the lower end of the social hierarchy had higher levels of cortisol, and thus stress.

• Humans have very similar social hierarchies to baboons but are by no means identical. Human hierarchies have much more mobility, for example. In human hierarchies it is easier for a male to change his social position than it is for a male baboon.

• Do the baboons have higher levels of cortisol because they are at the bottom of the hierarchy or are they at the bottom of the hierarchy because they have higher levels of cortisol? Which is really the DV here?

• Studies on humans showed similar results

To investigate the effects of a highly stimulating environment compared with the effects of an impoverished environment on rat’s brain growth

• Lab experiment

Rats were randomly allocated to 1 of 3 possible conditions:

• Impoverished, Enriched, or Control

All conditions had adequate food and water.

1. Control condition - a standard laboratory colony cage that contained several rats.

2. Impoverished condition - a slightly smaller cage isolated in a room in which the rat was placed alone.

3. Enriched environment - 6 to 8 rats in a larger cage furnished with a variety of objects with which they could play.

The rats lived in these environments for periods ranging from 4-10 weeks.

They were “humanely” killed so that autopsies could be carried out on their brains to see if any differences had developed.

The cerebral cortex of the enriched rats was significantly heavier and thicker than the impoverished rats.

The enriched environment rats also produced larger neurons than the impoverished rats and the synapses of the enriched rats’ brains were 50% larger than those of the impoverished rats.

It appears that an enriched environment may contribute to dentritic branching and to enhanced brain functioning.

• It is questionable to what extent we can generalize the findings from rats to human beings. However, there is research on humans that demonstrates similar results.

• To get autopsies of the rats, the animals had to be killed. There are ethical concerns about the killing of animals in research (RRR).

To investigate the role of monoamine oxidase A gene in aggressive behavior in mice.

Transgenic mice were used as part of this study that had a knocked out monoamine oxidase A (MAOA) gene.

A gene knockout is a genetic technique in which one of an organism's genes is made inoperative

The researchers carried out "resident-intruder" experiments to test the effect of the genetic variation, where a mouse was inserted into another mouse's cage.