IB Psychology Studies Flashcards - Paper 1

Aim of Antonova (2011)

Antonova (2011) wanted to see if scopolamine affected hippocampal activity in the creation of spatial memory. 

Method of Antonova (2011)

The researchers used a sample of twenty healthy male adults, with a mean age of 28 years old. The study used a double-blind procedure and participants were randomly allocated to one of two conditions. They were injected with either Scopolamine or a placebo 70 - 90 minutes before taking part in the experimental task. 

The participants were then put into an fMRI where they were scanned while playing the "Arena task."  This is a rather complex virtual reality game in which the researchers are observing how well the participants are able to create spatial memories.  The goal is for the participants to navigate around an "arena" with the goal of reaching a pole. After they have learned where the pole is located, the screen would go blank for 30 seconds.  During this time, the participants were told to actively rehearse how to get to the pole in the arena. When the arena reappeared, the participant was now at a new starting point in the arena. The participants would have to use their spatial memory to determine how to get to the location of the pole. 

The participants were first trained in the game to make sure that they were comfortable with the use of the joystick and that they understood the rules of the game.  After they were trained, they then took part in the experiment. The participants' brain activity was measured for six trials. 

The participants returned between 3 - 4 weeks later and redid the test - receiving the opposite treatment to the original study.  In other words, the study was a repeated measures design. 

Results of Antonova (2011)

The researchers found that when participants were injected with scopolamine, they demonstrated a significant reduction in the activation of the hippocampus compared to when they received a placebo.

Conclusion of Antonova (2011)

It appears that acetylcholine could play a key role in the encoding of spatial memories in humans, as well as in rats (link to Rogers and Kesner (2003))

Aim of Caspi (2003)

Caspi et al. (2003) aimed to explore the interaction between genetic predisposition and environmental stressors in the development of depression. Specifically, the study sought to test whether individuals with one or two copies of the short allele of the 5-HTT gene were more likely to develop depression in response to stressful life events, compared to individuals with two copies of the long allele.

The central research question was: "Does the presence of the short allele of the 5-HTT gene increase an individual's vulnerability to depression following stressful life events?"

This study was one of the first to offer strong empirical support for the gene-environment interaction hypothesis in mental health.

Method of Caspi (2003)

Method / Procedure: Design:

• Longitudinal, prospective study

• Conducted as part of the Dunedin Multidisciplinary Health and Development Study, a well-established birth cohort from New Zealand.

Sample:

• 847 participants (442 males and 405 females)

• All participants were of European descent, born in Dunedin, New Zealand, between April 1972 and March 1973.

• Participants were followed from birth to age 26, ensuring comprehensive developmental data.

• At age 26, participants were assessed for both genetic and psychological variables.

Genotyping:

• The 5-HTT gene (also called SLC6A4) has a polymorphism (variation) in its promoter region known as 5-HTTLPR.

• This polymorphism has two main allelic variants:

  • Short (s) allele – associated with reduced transcriptional efficiency and lower serotonin uptake.

  • Long (l) allele – associated with normal serotonin uptake.

Participants were divided into three groups based on their genotype:

1. s/s – two short alleles (approx. 17% of sample)

2. s/l – one short, one long allele (approx. 51% of sample)

3. l/l – two long alleles (approx. 31% of sample)

Data Collection Procedures: 1. Stressful Life Events (Ages 21–26):

• Life stress was measured using a modified Life Events Questionnaire.

• Events were categorized based on severity (e.g., financial problems, serious illness, job loss, relationship breakdown, etc.).

• Researchers counted the number of stressful life events experienced in the past five years (between ages 21–26).

• Stress exposure levels were classified as:

  • 0 events

  • 1 event

  • 2 events

  • 3 or more events

2. Depression and Mental Health Assessment (Age 26):

• Participants were assessed for Major Depressive Disorder (MDD) using the DSM-IV criteria, via the Diagnostic Interview Schedule (DIS).

• They were also evaluated for:

  • Self-reported depressive symptoms (e.g., feelings of sadness, hopelessness, sleep disturbance)

  • Suicidal ideation and suicide attempts

3. Longitudinal Depression History:

• Data was also collected on whether participants had experienced depressive episodes before age 21 (early-onset depression).

Results of Caspi (2002)

1. Gene Alone Did Not Predict Depression:

• The presence of the short allele alone (s/s or s/l) did not predict depression in the absence of stressful life events.

• This suggests that the gene does not cause depression by itself.

2. Gene × Environment Interaction:

• There was a significant interaction between the 5-HTT gene and the number of stressful life events:

  • Participants with two short alleles (s/s) who experienced three or more stressful events were more than twice as likely to develop depression compared to those with the l/l genotype.

  • Participants with one short allele (s/l) also had increased risk, but the effect was dose-dependent — those with two short alleles (s/s) were at greatest risk.

3. Cumulative Risk and Suicide:

• The same pattern held for suicidal ideation and suicide attempts:

  • s/s individuals who experienced multiple stressors were significantly more likely to report suicidal thoughts or attempts.

  • l/l individuals were largely resilient, even under multiple stress exposures.

4. Protective Effect of Long Allele:

• The long allele (l/l) appeared to confer a protective effect, acting as a buffer against the emotional consequences of stress.

Conclusion of Caspi (2003)

Conclusion:

• Caspi et al. (2003) concluded that the development of depression is influenced by an interaction between genetic vulnerability and environmental stress.

• The presence of the short allele of the 5-HTT gene increases the likelihood that stressful life events will trigger depressive episodes.

• This supports the diathesis-stress model: a diathesis (genetic vulnerability) + stressful experience → higher risk of psychopathology.

  Implications:

• The study marked a paradigm shift in psychology and psychiatry, moving away from purely biological or environmental explanations toward an integrated gene-environment approach.

• It suggested that genetic testing could eventually play a role in identifying at-risk individuals, although the ethical and practical applications are still debated.

• Highlighted the importance of personalized mental health interventions.

Aim of Maguire (2000)

Maguire et al. (2000) aimed to investigate whether the structure of the hippocampus, a brain region involved in spatial memory and navigation, would differ in London taxi drivers, whose jobs require extensive use of spatial navigation.

The researchers wanted to find evidence for neuroplasticity — the idea that the brain can structurally adapt in response to environmental demands and learning experiences.

Method of Maguire (2000)

Design:

• Quasi-experimental, correlational, cross-sectional study

• Used MRI scans and voxel-based morphometry (VBM) to compare brain structures

Participants:

• Experimental group:

  • 16 right-handed male licensed London taxi drivers

  • Mean age: ~44 years

  • All had completed the "Knowledge of London" test (which takes 2–4 years to prepare for)

  • Average of 14.3 years driving experience

• Control group:

  • 50 right-handed healthy males

  • Matched for age, health, and handedness

  • Not taxi drivers

  • Recruited from an existing MRI database

Procedure:

• Participants underwent structural MRI scans.

• The scans were analyzed using:

  1. Voxel-Based Morphometry (VBM) — assessed grey matter volume across the entire brain

  2. Pixel counting — manual measurement of hippocampal volume based on slice images from the MRI

• Researchers compared the hippocampal volume between taxi drivers and non-drivers, specifically examining:

  • Posterior hippocampus (linked to spatial memory/navigation)

  • Anterior hippocampus (linked to memory encoding and new learning)

Results of Maguire (2000)

• Increased posterior hippocampal volume:

  • Taxi drivers had significantly more grey matter in the posterior hippocampus, particularly on the right side, compared to controls.

• Decreased anterior hippocampal volume:

  • Taxi drivers had less grey matter in the anterior hippocampus than non-taxi drivers.

• Positive correlation with driving experience:

  • A significant positive correlation was found between the number of years spent as a taxi driver and the volume of the posterior hippocampus.

  • The longer a person had been driving a taxi, the larger their posterior hippocampus was.

Conclusion of Maguire (2000)

The study provides strong evidence for neuroplasticity in the adult brain. The structural differences found in the hippocampus of taxi drivers suggest that intensive use of spatial navigation skills leads to brain reorganization, specifically increased grey matter volume in the posterior hippocampus.

The findings support the idea that the brain can change structurally in response to environmental challenges and repeated cognitive tasks. In this case, long-term use of spatial memory led to physical changes in the brain.

This study also supports localization of brain function, as different parts of the hippocampus (posterior vs. anterior) appear to serve different functions.

Aim of Draganski (2004)

Draganski et al. (2004) aimed to investigate whether learning a new skill (in this case, juggling) would lead to detectable structural changes in the brain, specifically in grey matter volume, thereby providing evidence for neuroplasticity in adults.

The study explored the idea that repeated motor and visual-spatial activity over time would lead to brain adaptation — a key concept in understanding experience-dependent brain plasticity.

Method of Draganski (2004)

Design:

• Experimental, longitudinal design

• Repeated-measures design — same participants scanned multiple times

• Used MRI scans to observe changes in brain structure over time

Participants:

• 24 volunteers (aged 20–24 years)

  • 21 females, 3 males

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

• Randomly assigned to one of two groups:

  • Juggling group (experimental)

  • Non-juggling group (control)

Procedure:

1. Baseline Scan:

   • All participants had an initial MRI scan to measure brain structure before any training began.

2. Training Phase (3 months):

   • The juggling group was instructed to learn a three-ball cascade juggling routine.

   • Practiced for at least 60 seconds per day over a 3-month period.

   • After mastering the routine, they returned for a second MRI scan.

3. No-Practice Phase (3 months):

   • Participants stopped practicing juggling for 3 months.

   • A third MRI scan was taken after this period to assess whether any changes persisted or reversed.

4. Control group:

   • Did not learn juggling

   • Also underwent MRI scans at the same intervals for comparison

Analysis Technique:

• Voxel-based morphometry (VBM) was used to measure changes in grey matter density in specific brain regions.

Results of Draganski (2004)

• After 3 months of juggling practice:

  • The juggling group showed a significant increase in grey matter volume in two brain regions:

    • Mid-temporal area (part of the visual processing pathway — especially motion)

    • Left posterior intraparietal sulcus (involved in visuomotor coordination)

• After 3 months without juggling:

  • Grey matter volume in those regions decreased but remained higher than baseline.

  • Suggests that brain changes are activity-dependent and partially reversible if the activity stops.

• Control group:

  • Showed no significant changes in grey matter volume across the three MRI scans.

Conclusion of Draganski (2004)

• The study provides strong evidence that learning a new motor skill (juggling) leads to structural changes in the brain, supporting the concept of neuroplasticity.

• These changes were observed in regions associated with visual motion processing and visuomotor coordination, suggesting that the brain adapts to meet the cognitive demands of the new skill.

• The increase and subsequent decrease in grey matter volume also highlight that neuroplastic changes are reversible — the brain adapts based on how often a skill is practiced or used.

This supports the view that the adult brain remains plastic, and that even short-term learning can induce measurable physical changes in brain structure.

Aim of Case Study of HM (Henry Molasion)

Although the case study of HM spans multiple decades, the central aim of the long-term research was to understand:

• The role of the hippocampus in the formation of long-term memories

• The relationship between brain structures and memory functions, especially the biological basis of memory

Following a surgical procedure to control epilepsy, HM developed profound anterograde amnesia, making him a critical case for understanding the link between brain structures and behavior, particularly memory formation.

Method of Case Study of Henry Molasion (HM)

This case was investigated longitudinally over several decades, primarily by Brenda Milner and later by Corkin et al., using a combination of:

• Cognitive and neuropsychological testing

• Interviews and observations

• MRI brain imaging (later, in the 1990s and 2000s)

• Experimental memory tasks, such as:

  • Mirror-drawing task (to assess procedural memory)

  • Word recall tasks (to assess declarative memory)

Results of Case Study of Henry Molasion (HM)

1. Memory Impairments:

• HM had anterograde amnesia: He could not form new explicit (declarative) memories after the surgery.

• His short-term memory (e.g., digit span of ~20 seconds) remained intact.

• His long-term memories from before the surgery (especially those from early life) were largely preserved.

• He could not transfer information from short-term memory to long-term memory, showing a clear disruption in memory consolidation.

2. Types of Memory:

• Procedural (implicit) memory was unaffected:

  • He was able to learn new motor skills (e.g., mirror-drawing) over time but had no conscious memory of having learned the task.

• Declarative (explicit) memory was severely impaired:

  • He could not recall events, people, or facts encountered after the surgery.

3. Localization of Function:

• Research indicated that the hippocampus plays a critical role in the consolidation of explicit long-term memories, especially episodic and semantic memory.

• His ability to learn motor skills despite hippocampal damage suggested that memory is not a unitary function and different types of memory are localized in different brain areas.

4. Brain Imaging (later findings):

• MRI scans conducted in the 1990s by Corkin et al. (1997) confirmed:

  • Bilateral damage to the hippocampus, amygdala, and parts of the medial temporal lobe.

  • Surrounding brain structures were mostly intact.

Conclusion of HM Case Study

The case of HM provides strong evidence for the relationship between specific brain structures and memory functions, contributing to our understanding of:

• Localization of function: The hippocampus is essential for the formation of new long-term declarative memories.

• Brain and behavior: Damage to specific brain areas (hippocampus) leads to specific behavioral consequences (anterograde amnesia).

• Memory systems: Supports the theory that explicit and implicit memory systems rely on different neural substrates.

HM’s case became foundational in cognitive neuroscience and has influenced memory research, neuropsychology, and clinical approaches for decades.

Aim of Newcomer et al., (1999)

The aim of Newcomer et al. (1999) was to investigate the effects of the stress hormone cortisol on verbal declarative memory in healthy humans.

The researchers wanted to determine whether high levels of cortisol, similar to those produced in response to chronic stress, would have a negative effect on memory performance, particularly in relation to the hippocampus, which is known to be involved in memory consolidation.

Method of Newcomer et al., (1999)

Method / Procedure: Design:

• Double-blind, laboratory, experimental design with independent groups.

• Participants were randomly assigned to one of three experimental conditions.

Participants:

• 51 healthy adults aged 18–30

• Screened for medical/psychological health to ensure no existing memory impairments or hormone irregularities

Procedure:

Participants were randomly allocated to one of three conditions for four days:

1. High cortisol group:

   • Given 160 mg of cortisol per day

   • This dosage simulates levels seen in high stress situations

2. Low cortisol group:

   • Given 40 mg of cortisol per day

   • Represents mild stress levels

3. Placebo group:

   • Given placebo tablets (no active hormone)

All participants were then asked to perform a verbal declarative memory task:

• The task involved listening to and recalling parts of a prose paragraph.

• Performance was measured based on accuracy of recall immediately after the task and after a delay.

• Memory tests were repeated multiple times during the four-day period.

Results of Newcomer et al., (1999)

1. High cortisol group:

   • Showed significantly worse memory performance on the verbal declarative memory task compared to the placebo group.

   • Performance declined specifically in the early days of exposure.

   • Memory impairment was reversible — performance returned to normal after cortisol levels dropped.

2. Low cortisol group:

   • No significant memory impairment compared to the placebo group.

   • Some slight improvement was noted, but it was not statistically significant.

3. Placebo group:

   • Maintained consistent performance across all sessions.

Conclusion of Newcomer et al., (1999)

• The study concluded that elevated cortisol levels impair verbal declarative memory, likely due to cortisol's negative effect on the hippocampus.

• This supports the theory that chronic stress or high cortisol levels can disrupt cognitive functioning, particularly explicit memory processes.

• The findings contribute to our understanding of how hormones influence behavior, showing that biological responses to stress can have direct, measurable impacts on memory.

Aim of Dabbs et al., (1995)

The aim of Dabbs et al. (1995) was to investigate the relationship between testosterone levels and types of criminal behavior among male prison inmates.

Specifically, the study examined whether higher testosterone levels were associated with increased aggressive and violent behavior, both in terms of the type of crime committed and the inmate's behavior in prison.

Method of Dabbs et al., (1995)

Design:

• Correlational, quasi-experimental field study conducted in a naturalistic prison setting

Participants:

• 692 male prison inmates in federal and state prisons in the United States

• Wide range of ages, ethnicities, and criminal histories

Procedure:

1. Testosterone Measurement:

   • Saliva samples were collected from each inmate to measure free testosterone levels using radioimmunoassay techniques.

2. Criminal Record Review:

   • Participants were categorized based on the type of crime:

     • Violent crimes (e.g., homicide, assault, armed robbery, rape)

     • Non-violent crimes (e.g., burglary, drug offenses, theft, embezzlement)

3. Prison Behavior Assessment:

   • Prison records were reviewed to document behavioral incidents, including:

     • Aggression (e.g., fights, threats)

     • Rule violations

     • Disciplinary actions

   • These were used to evaluate dominance-related behaviors during incarceration.

Results of Dabbs et al., (1995)

• Testosterone and Type of Crime:

  • Inmates who had committed violent crimes had significantly higher testosterone levels than those who had committed non-violent crimes.

• Testosterone and Prison Behavior:

  • Inmates with higher testosterone levels also displayed more dominant and aggressive behaviors while in prison.

  • This included more rule violations, more confrontations, and higher rates of physical aggression.

• Appearance and Personality Traits:

  • Inmates with higher testosterone levels were rated by observers as more masculine, dominant, and aggressive in their demeanor and body language.

Conclusion of Dabbs et al., (1995)

• The study supports a correlational relationship between testosterone levels and aggressive, dominant behavior in both criminal history and prison conduct.

• It suggests that testosterone may influence behavior related to violence and dominance, although it does not prove causation.

• The results contribute to the understanding of how biological factors (hormones) can influence social behavior such as aggression and criminality.

Aim of Ludstrom and Olsson (2005)

Lundström & Olsson (2005) aimed to investigate the effect of the putative human pheromone androstadienone on female mood and behavior, particularly in the presence of a male or female experimenter.

The researchers hypothesized that androstadienone may act as a chemosignal (a pheromone-like substance) that influences social and sexual behavior in humans, and that its effects may be context-dependent — i.e., enhanced in the presence of males.

Method of Ludstrom and Olsson (2005)

Method / Procedure: Design:

• Double-blind, laboratory experiment

• Independent measures design

Participants:

• 37 heterosexual women, average age in early 20s

• All had normal sense of smell

• Tested during the same phase of their menstrual cycle to control for hormonal variability

Procedure:

1. Participants were exposed to androstadienone dissolved in a clove oil base (to mask the natural scent) or to clove oil alone (control).

2. They were randomly assigned to interact with either:

   • A male experimenter, or

   • A female experimenter

3. After exposure, participants completed a series of mood questionnaires and psychological tests to assess emotional and cognitive responses.

4. Mood was assessed using standardized self-report measures such as Positive and Negative Affect Scales (PANAS).

Results of Ludstrom and Olsson (2005)

• In the presence of a male experimenter, women exposed to androstadienone reported significantly higher positive mood, compared to those exposed to the control scent.

• No significant mood effect was observed when the experimenter was female.

• Androstadienone did not affect cognitive task performance, suggesting the effect was emotional or social, rather than purely cognitive.

Conclusion of Ludstrom and Olsson (2005)

• The study supports the idea that androstadienone affects female mood in a context-dependent manner, specifically when exposed to male presence.

• This suggests that androstadienone may act as a human chemosignal (pheromone) that modulates emotional responses, potentially enhancing social or sexual communication.

• The effect was not general, but socially specific — implying that pheromones may function interactively with social context rather than in isolation.

Hare et al., 2017 - Aim

To investigate if androstadienone and EST signal gender and affect mate perception.

Hare et al., 2017 - Method

140 heterosexual participants took part in an experiment; repeated measures design. Participants completed two computer-based tasks on two consecutive days. On one of the days they were exposed to the putative pheromone (AND or EST) masked with clove oil; on the other day they were exposed to the control scent (clove oil alone). The order of conditions was counterbalanced.  

Task 1: participants were shown five “gender neutral facial morphs” and had to indicate the gender (male or female)  

Task 2: they were shown photographs of the opposite sex and asked to rate their attractiveness on a scale from 1 to 10.  

Hare et al., 2017 - Results

There was no difference in gender assigned to the faces in the pheromone versus control condition. There was no difference in the average attractiveness ratings of the photographs of the opposite sex.  

Hare et al., 2017 - Conclusion

the two chemicals (AND and EST) do not act as signals of gender or of attractiveness. Based on this result, researchers concluded that these chemicals do not qualify as human pheromones. 

Caspi (2002) - Aim

To investigate why some children who are maltreated grow up to develop antisocial behaviour, whereas others do not & to investigate whether antisocial behavior would be predicted by an interaction between a gene (MAOA) and an environment. 

Caspi (2002) - Method

Participants:  

A large sample of 442 male children was followed from birth to adulthood. they were assessed at ages 3, 5, 7, 9, 11, 13, 15, 18, and 21 and finally at 26 (96%) 

 

Method:  

1. the sample was genotyped  
2. environmental factors (forms of maltreatment) were assessed. between ages 3-11, 154 children had been maltreated. 8% experienced severe maltreatment, 28% probable maltreatment, 64% no maltreatment. (maltreatment included physical abuse resulting in injury, sexual abuse, rejection by the mother, and frequent changes of primary caregiver). maltreatment groups did not differ in MAOA activity.  
3. antisocial behaviour was measured by using clinical diagnosis of conduct disorder; personality checklists to measure antisocial personality traits; official conviction records for violent offences (assault, robbery, rape, domestic violence, homicide) 

Caspi (2002) - Results

85% of the males having low-activity MAOA gene genotype who were severely maltreated developed some form of antisocial behavior. Maltreated children with a genotype conferring high levels of MAOA expression were less likely to develop antisocial problems. Males with high MAOA activity did not have elevated antisocial scores even when they had experiences childhood maltreatment. 

Caspi (2002) - Conclusion

The findings may partly explain why not all victims of maltreatment grow up to victimize others, and they provide epidemiological evidence that genotypes can moderate children's sensitivity to environmental insults. (genotype cannot predict violence in a full sample; increased risk for violence is activated by childhood maltreatment) 

Kendler (2006) - Aim

to carry out a twin study of over 42,000 twins from the Swedish national twin registry to determine the level of heritability of depression. 

Kendler (2002) - Method

Lifetime major depression was assessed at personal interview by modified DSM-IV criteria in 42,161 twins, including 15,493 complete pairs, from the national Swedish Twin Registry.  

Kendler (2006) - Results

They found that the average concordance rate for MZ male twins was 31 per cent and for MZ female twins 44 per cent, while for DZ twins it was 11 and 16 per cent respectively.  

Kendler (2006) - Conclusion

Overall, Kendler concluded that heritability of depression is estimated to be 38%.  

Weissman (2005) - Aim

To study the potential genetic nature of Major Depressive Disorder.   

Weissman (2005) - Method

Weissman et al (2005) carried out a longitudinal family study with a sample of 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, researcher 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.  

Weissman (2005) - Results

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. On the other hand, if a parent was depressed but there was no history of depression in the grandparents, there was no significant effect of parental depression on the grandchildren. 

Weissman (2005) - Conclusion

The association between parental MDD and child diagnosis is moderated by grandparental MDD status. The rates of psychopathology are highest in grandchildren of parents and grandparents with a moderately to severely impairing depression. Anxiety disorders are the early sign of psychopathology in the young grandchildren.  

Fessler et al., 2005 - Aim

To investigate whether disgust sensitivity is adjusted as a function of the immune system, by testing the hypothesis that disgust sensitivity varies across pregnancy in a manner that compensates for changes in the vulnerability to disease. 

Fessler et al., (2005) - Method

Using a web-based survey of 496 pregnant women, with an average age of 28 years old, the researchers compared the disgust sensitivity of participants in their first trimester with those in later stages of pregnancy. 155 participants were in the first trimester, 183 in the second trimester and 158 in the third trimester. Responses from women who were in the second and third trimesters at the time of participation were pooled and compared with the responses from women who were in the first trimester. 

Fessler et al., 2005 - Results

Analysis revealed that participants in the first trimester reported greater overall disgust sensitivity than did participants in the second and third trimesters, and they also experienced more nausea. A simple correlational analysis revealed that overall disgust sensitivity was positively related to the current level of nausea throughout pregnancy. 

Fessler et al., 2005 - Conclusion

These results provide support for the hypothesis that disgust sensitivity varies during pregnancy in a manner that compensates for maternal and foetal vulnerability to disease. 

Curtis et al., 2004 - Aim

To test the hypothesis that disgust is an adaptation that serves to prevent disease. 

Curtis et al., 2004 - Method

A survey instrument was placed on the BBC Science website and completed by over 77,000 people from 165 countries. Once improbable data had been removed, and those who had already seen a BBC programme that alerted them to the hypothesis were also removed, this left just under 40,000 respondents. Respondents were asked to rate 20 photographs, which appeared one-by-one on separate web pages, for disgust on a scale of 1–5. Randomly placed among the 20 photographs were seven pairs: one depicting a disease-salient stimulus and another matched to be as similar as possible, but without disease relevance. 

A final question on the Web site asked respondents to choose with whom they would least like to share a toothbrush. 

Curtis et al., 2004 - Results

All seven of the disease-salient images were rated as more disgusting by females than males rated them. Feelings of disgust decreased with age, and in response to the final question regarding with whom participants would least like to share a toothbrush, the least acceptable was the postman (59.3%), followed by the boss at work (24.7%), the weatherman (8.9%), a sibling (3.3%), a best friend (1.9%) and the spouse/partner (1.8%). Results were also consistent across cultures. 

Curtis et al., 2004 - Conclusion

This gender-bias in the result is consistent with women’s enhanced evolutionary role in protecting the next generation. 

Disgust is a biologically based response to disease-salient stimuli that reduces the risk of disease…  

The decline with age is explained by the fact that older people have finished their reproductive life and are therefore evolutionarily disposable, and finally, the preference for toothbrush-sharing with a partner rather than a stranger is explained thus: sharing a person’s bodily fluids becomes more disgusting as that person becomes less familiar because strangers are more likely to carry new diseases and hence present a greater threat to another person’s immune system. 

Rogers and Kesner (2003) - Aim

The aim of the study was to determine the role of acetylcholine in the formation of spatial memory. 

Rogers and Kesner (2003) - Method

Rogers & Kesner wanted to determine the role of acetylcholine in memory formation and retrieval. They had 30 rats acclimate to a Hebb Williams maze by placing food in one of the corners.  Once the rats were familiar with the maze - and no longer were afraid of the environment - the experiment could begin. 

The rats were randomly allocated to one of two conditions. The rats were either injected with scopolamine or with a saline solution ten minutes before running the maze. Scopolamine blocks the acetylcholine receptor sites and thus inhibits any response.  The saline solution was a placebo injection. This was done to make sure that the fact of getting an injection alone was not responsible for a change in memory. An injection could result in an increase in adrenaline which would be a confounding variable. The injections were made directly into the hippocampus. 

Encoding of memory was assessed by the average number of errors made on the first five trials of Day 1 compared to the last five trials of Day 1, whereas the average number of errors made on the first five trials of Day 2 compared to the last five trials of Day 1 was used to assess retrieval. 

Rogers and Kesner (2003) - Results

The findings were that the scopolamine group took longer and made more mistakes in the learning of the maze - that is, there was a higher average number of mistakes made on the last five trials on Day 1. However, it did not appear to have an effect on retrieval of memories that had already been created.  

Rogers and Kesner (2003) - Conclusion

It appears that acetylcholine may play an important role in the consolidation of spatial memories. 

Rosenweig and Bennet (1972) - Aim

In this classic study, Rosenzweig, Bennet & Diamond wanted to see if changing the level of stimuli in the environment would result in physical changes in the brain.  The aim of the study was to investigate whether environmental factors such as a rich or an impoverished environment would affect the development of neurons in the cerebral cortex. 

Rosenweig and Bennet (1972) - Method

Three male rats from a common litter were randomly allocated to one of three environments. In the control condition [CC] there were three rats in the cage. In the impoverished condition [IC], the researchers placed each rat in individual cages. The individual cages lacked the toys and the maze which were in the enriched environment. For the enriched condition [EC], the researchers placed 10 - 12 rats in a cage containing different stimulus objects to explore and play with. All groups had free and adequate access to food and water. 

The rats typically spent 30 to 60 days in their respective environments before they were killed in order for the researchers to study changes in the brain's anatomy. 

Rozenweig and Bennet (1972) - Results

The anatomy of the brain was different in the EC and the IC. There was an increased thickness and higher weight of the cortex in EC rats compared to that of IC rats. The researchers also noted that rats in the EC condition had developed significantly greater activity in the neurons in the cerebral cortex associated with transmission of acetylcholine, which is an important neurotransmitter for learning and memory. 

It appears that the thickness of the cortex and the overall weight of the brain increased as a result of the enriched environment. A follow-up to this research indicated that just 30 minutes a day in an enriched environment produced the same changes in the brain in rats as had been observed in the original experiment where rats were exposed to the EC condition for a much longer period of time. 

Rozenweig and Bennet (1972) - Conclusion

Since brain plasticity is assumed to follow the same pattern in both animals and humans, the implications of the study are that the human brain should also be affected by environmental factors such as intellectual and social stimulation. It is now known that poverty is a major risk factor in children’s cognitive development as poverty is related to a number of risk factors such as poor nutrition, lack of access to good education and poor health. 

Albert et al., (1986) - Aim

 Investigate how testosterone influences aggression in "alpha male" rats 

Alber et al., (1986) - Method

Procedure: Rats were placed in cages, and the alpha male rats were identified.  (Alpha males are typically the largest males, who are the most dominant and aggressive).  The alpha males were then randomly assigned to one of four conditions: 

 

A. Castration (i.e. removal of the testicles, which causes a large drop in testosterone) 

B. Castration, followed by implanting tubes with testosterone 

C. Castration, followed by implanting empty tubes 

D. A "sham" operation, in which the rats were cut open & then sewn up, with no castration 

Albert et al., (1986) - Results

The rats whose testosterone levels were diminished (conditions A and C) displayed less aggressive behaviors, such as less biting of other rats.  The rats whose testosterone levels remained the same (conditions B and D) continued to display the same level of aggression.  

 

Furthermore, when the lowered testosterone rats (conditions A and C) were placed in a cage with another rat, the second rat then took on the role of the "alpha", becoming more aggressive to the rat with the diminished testosterone. 

Albert et al., (1986) - Conclusion

Testosterone plays an important role in aggression and status-seeking in rats.  Higher testosterone increases aggression and dominance of other rats. 

Meaney (1988) - Aim

The aim of the study was to determine the effect of glucocorticoids (stress hormones) on memory.

Meaney (1988) - Method

• Meaney and his team used an independent samples design. The rats were randomly allocated to one of two conditions.  

• Treatment group: 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 they 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. This group served as the control condition. 

• To test the effect of these elevated rates of stress hormones over their lifetime, two-year old rats were put into a pool of milky water. In the pool was a platform. Meaney and his team tracked the route of the rats as they sought out the platform based on the rats' memories of previous attempts to escape the water. 

Meaney (1988) - Results

• 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.  Increased exposure to adrenal glucocorticoids accelerated hippocampal neuron loss and cognitive impairments in aging. 

• You can see that the rats taken away from their mothers at a young age and were not groomed by the researchers took a much more circuitous route to get to the platform when they reached old age. 

Meaney (1988) - Conclusion

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. It appears that the extra stroking that the rats received led to an activation of genes which are responsible for the reaction to the stress response. This is an example of epigenetics - the grooming process “turns on” the genes which help the young rat cope with stress - which then leads to a longer and healthier life. 

Cases et al (1995) - Aim

Cases et al (1995) carried out a study on the genetic origins of aggression.

Cases et al (1995) - Method

Cases et al (1995) carried out a study on the genetic origins of aggression. For their study, they used a transgenic mouse where the gene that regulates the production of monoamine oxidase A (MAOA), an enzyme that breaks down serotonin and norepinephrine, was ‘knocked out” or deleted. 

Between days 11 and 16, the transgenic mice showed several signs of low MAOA, including frantic running, violent shaking during sleep and a tendency to bite the experimenter. In adult males, they observed signs of offensive aggressive behaviour - including bite wounds. 

To test the effect of the genetic variation, the researchers carried out "resident-intruder" tests, where a mouse was introduced into the cage of another mouse. With control mice, when the "intruder" was introduced, the mice would "check out" the other mouse, sniffing and engaging with the mouse. 

Cases et al (1995) - Results

In the transgenic mice, the mice adopted a threatening hunched position and would engage in aggressive behaviour.  This was also true in the case where the intruder was a female mouse. 

Autopsies of the brains of the mice showed an increase in serotonin, dopamine, and norepinephrine.  Although dopamine was not highly elevated, serotonin levels were six to nine times higher than the control mice. 

Cases et al (1995) - Conclusion

The study showed that the genetic variation led to MAOA deficient mice that exhibited strong aggressive behaviour.  The researchers concluded that when human males lack MAOA and demonstrate aggressive behaviour, the behaviour cannot be attributed to social factors. Instead, the MAOA deficiency is a predisposition toward aggressive behaviour which may be expressed through interaction with social and environmental factors. 

Caspi et al (2010) - Aim

To support the claim that the ss alleles make people more 

sensitive and reactive to the environment and a greater risk for  

depression as Rhesus monkeys have the same 5-HTT polymorphisms as humans. 

Caspi et al (2010) - Method

Some baby Rhesus monkeys were taken from their mothers and raised with peers and some stayed with their mothers. Clear patterns of behaviour emerged. 

Caspi et al (2010) - Results

Showed that monkeys with the long allele of 5-HTT protested their situation less. In addition they showed effective coping skills appropriate for monkeys. Monkeys with the short allele showed more anxiety and had decreased amount of serotonin in their spinal fluid as compared to monkeys with the short allele raised under normal living conditions.  

Caspi et al (2010) - Conclusion

Monkeys with short allele are at greater risk of depression