Biological Approach

Question 1

Localization of
Functions

Answer 1

Localization of Functions - Refers to the idea that behaviors, emotions, and thoughts originate in the brain in specific locations
Memory - The ability to encode, store, retain and recall information. This is localized in the hippocampus
Episodic Memory - The capacity of recollecting personal memories
Semantic Memory - The capacity of recollecting general knowledge
Procedural Memory - The capacity of recollecting physical skills (not localized in hippocampus)
Spatial Memory - The capacity of recollecting memories related to the placement of an object. Studies: Maguire et al. (2000) and Brenda Milner (1957)

Question 2

Brenda Milner (1957) - HM

Answer 2

Aim: Demonstrate the role of the hippocampus on semantic and episodic memory
Case Study/triangulation- 7 yo HM suffered from a brain injury from his bike. Had constant seizures until the age of 27, he finally got a surgery and removed ⅔ of hippocampus. After this operation, HM suffered from retrograde and anterograde amnesia.
Milner wanted to test how this removal affected memory. She performed various IQ tests, cognitive tasks (star task) and direct observations.
Findings: HM improved in his procedural memory (drawings) however he always forgot where that was learned from. He couldn’t store episodic nor semantic memories.
Corkin (1997) preformed an MRI to show damage.
Ethics: informed consent by proxy

Question 3

Maguire et al. (2000) - Taxi Drivers

Answer 3

Aim: Demonstrate the role of neuroplasticity in the hippocampus in the formation of spatial memory
Participants: 16 male right-handed taxi drivers with at least a 1.5 years driving experience and 50 non taxi drivers that were taken from a database
Procedure: Quasi Exp. Participants were put under an MRI to investigate the hippocampus
Findings: Taxi drivers have a larger posterior hippocampus and decreased anterior (shows spatial memory is localized here). Also shows dendritic branching since the posterior hippo expanded as an individual had more experience

Question 4

Brain Scanning Techniques

Answer 4

MAGNETIC RESONANCE IMAGING
- Widespread since the 1980s
- Uses magnetic fields, radio waves, and computer to take images of slices of the brain. Shows structure only. Can be 2D or compiled into 3D images.
- Magnet changes proton alignment in body water. When molecules ‘spin’, the computer reads the motion and creates the image.
- Strengths: non-invasive, no-radiation, more precise, can be repeated. - Limitations: Only structure, not a natural environment→ artificial research, shading may be exaggerated, patient distress, can’t have metal on your body.
FUNCTION MAGNETIC RESONANCE IMAGING
- Like an MRI and PET scan combined - shows both structure and function - Works with a magnet like an MRI but measures blood flow instead of water molecules. Oxygen-rich blood reacts differently to the magnet than oxygen-poor blood. The computer senses this and creates an image where oxygen is being used for brain function. This creates a colored image like a PET scan.
- Strengths: Most advanced and recent, Good resolution, shows on-going thinking, no radiation like PET scans
- Limitations: Expensive, time delay for blood to get there- is activity still happening? You can get false positives, some colors hidden or exaggerated- seems like the area is not working but maybe just efficient and needs less oxygen (works in real-time)
Studies: Maguire et al. (2000) and Fisher et al. (2003)

Question 5

Fisher et al. (2003) - fMRI and Dopamine

Answer 5

Aim: To investigate a possible link between dopamine rich brain regions and the early stages of romantic love
Participants: A self-selected sample of 10 female and 7 male students from New York State University, mean age = 20 years. All participants reported that they were ‘in love’ for a mean of 7.5 months.
Procedure: Correlational study- Participants were placed in an fMRI scanner and shown a photograph of their romantic partner followed by a distraction task and then a ‘neutral’ photograph of an acquaintance with whom they had no emotional connection all of this was done after completing the passionate love scale questionnaire.
Findings: The fMRI showed that the areas of the brain most active when the photograph of the romantic partner was viewed were the right ventral tegmental areas in the midbrain. (known to operate the reward system and dopamine production)
Conclusion: People who are in the early stages of romantic love may access brain regions associated with dopamine release when in the presence (physical or virtual) of their romantic partner. Therefore, it could be said that people become ‘addicted to love’
Evaluation:
Strengths- The findings support previous research into the role of dopamine in substance addiction so it is interesting to see how romantic love may fall under the same framework of craving and withdrawal
- The use of fMRI clearly shows a link between dopaminergic areas of the brain only when the photograph of the romantic partner was shown which increases the internal validity of the study i.e. Fisher really was measuring the effect of romantic love on the brain
Limitations
- There could be other explanations for the activation of the dopamine-rich areas of the brain being active during the fMRI e.g. excitement at taking part in a study; curiosity as to the outcome of the study, so - Fisher cannot claim cause-and-effect from her findings

Question 6

Neurotransmitters and Behavior

Answer 6

Effects of Neurotransmitters - This doesn’t refer to a neurotransmitter’s function, but rather how they work to affect the brain’s chemistry

Excitatory Nts - These promote the activation and firing of neurons by making an action potential
Inhibitory Nts - They inhibit or dampen neuronal activity by disrupting the action potential

Agonists - Mimics the effects of neurotransmitters
Antagonists - Opposes the effects of neurotransmitters
Studies: Prevot et Al. (2019) - Agonist and Inhibitory
Antonova (2011) - Antagonist and Excitatory

Question 7

Prevot et al. (2019) - Agonist and Inhibitory

Answer 7

Aim: The effects of imidazobenzodiazepine as an agonist to increase memory
Procedure: lab exp. rats were put in a y maze repeatedly to test their spatial memory. Then the rats ran through the maze again, after they were either injected with a placebo or an agonist drug (imidazobenzodiazepine). Findings: The rats that went into the same arm of the Y twice were considered to have worsened memory, but those who were injected with the agonist preformed better the second time. Demonstrating that the inhibition of GABA increases memory. Ethics: Sacrificed rats

Question 8

Antonova (2011) - Antagonist and Excitatory

Answer 8

Aim: To investigate the effects of scopolamine (antagonist) in the hippocampus when creating spatial memories.
Participants: 22 adults, mean age of 28
Procedure: Individuals were placed in two conditions, those injected with scopolamine which is an antagonist to AcH receptors and those given a placebo prior to the task. They were then placed in an fMRI and asked to do the arena task where they walk around until they find a pole, once It’s found it restarts, and they had to start from a different location in the map. This created spatial memory over the 6 trials. 3 weeks later, they came back for a repeated measure design.
Findings: The activation was lower in the hippo in the individuals in the first condition, thus indicating hat the excitatory synapses of acetylcholine for a reduction of activity.

Question 9

Neurotransmission

Answer 9

Neurotransmission - This is the process through which neurotransmitters communicate to induce certain behaviors
Romantic Love - Behavior characterized by a combined feeling of obsession and attraction to a specific individual
Dopamine - Neurotransmitter usually associated with addiction
Serotonin - Neurotransmitter usually associated with obsession
Studies: Fisher et al. (2003) - dopamine fMRI and Marazziti (1999) - Serotonin and blood samples

Question 10

Marazziti (1999) Serotonin and OCD

Answer 10

Aim: To explore how serotonin affects romantic love and obsessive-compulsive disorder (OCD).
Participants: 60 individuals divided into three groups—20 in early stages of romantic love self selected, 20 diagnosed with OCD, and 20 controls.

Procedure: Investigating the hypothesis that individuals in love exhibit similar obsessive behaviors as those with OCD, who are known to have low serotonin levels, the study measured serotonin levels through blood samples from each participant.

Findings: Individuals in love had lower serotonin levels compared to those with OCD, who in turn had significantly lower levels than the control group. The study suggests that low serotonin levels may contribute to obsessive thinking in romantic love, similarly observed in OCD, although attributing this solely to serotonin may be overly reductionist.
Love is like an addiction.

Question 11

Neuroplasticity

Answer 11

Neuroplasticity - This is the brain’s ability to rearrange neurons based on past experiences and environmental influences
Dendritic Branching - When experiences expand the neural connections in the brain
Synaptic Pruning - When unused synapses fade away to allow for other synaptic connections
Visual Memory - The capacity of recollecting skills related to sight
Spatial Memory - The capacity of recollecting memories related to the placement of an object
Studies: Maguire et al. (2000) Branching and Dragonski et al. (2004) Pruning

Question 12

Dragonski et al. (2004)

Answer 12

Aim: The study aimed to determine whether acquiring new skills through juggling would lead to structural changes in the brain.

Participants: The study included 24 volunteers without prior juggling experience. They were divided into two groups: jugglers and non-jugglers (control group).

Procedure: The participants in the juggling group were trained to juggle three balls with increasing complexity over a three-month period. Both groups underwent MRI scans at the beginning of the study, after the three-month training period, and again three months after the training had ended.

Findings: The results showed that the jugglers experienced significant gray matter increases in the mid-temporal area and areas associated with visual motion processing. These changes were not observed in the control group. Furthermore, these changes were partially reversed when the jugglers stopped practicing, suggesting the brain’s plasticity in response to learning and unlearning new skills.

Question 13

Hormones and Behavior

Answer 13

Hormones - They’re chemical messengers that communicate through the bloodstream to induce behaviors
Declarative Memory - Refers to memories that can be declared verbally
Cortisol - This is a hormone that induces stress, therefore it’s theorized to affect declarative memory
Emotional Memories - Refers to memories formed through emotional connections
Adrenaline - This is a hormone that induces emotional connections by communicating to the amygdala that something dangerous or important is happening
Studies: Newcomer et al. (1999) Cortisol and McGaugh and Cahill (1995) - Adrenaline

Question 14

Newcomer et al. (1999) Cortisol

Answer 14

Aim: To investigate the effects of cortisol on declarative memory when feeling stressed.
Participants: The study involved 51 healthy participants, aged 18-30 years, who were randomly assigned to one of three groups: high cortisol doses 160mg, low cortisol doses 40 mg, or placebo.

Procedure: The study spanned four days, during which participants in the high and low dose groups received either 160 mg or 40 mg of cortisol daily, respectively, while the placebo group received no active medication. The participants underwent verbal declarative memory tests both before and after the treatment period.

Findings: The findings revealed that participants receiving high doses of cortisol exhibited a significant decrease in their verbal declarative memory performance compared to both the low dose and placebo groups. The results suggest that prolonged exposure to elevated levels of cortisol, can impair memory functions, highlighting the potential cognitive side effects of steroids used in medical treatments.
Strengths: double-blind procedure to eliminate bias

Question 15

McGaugh and Cahill (1995) - Adrenaline

Answer 15

Aim: To investigate the effects of adrenaline on the amygdala during the formation of emotional memories.

Participants: 18 Participants were divided into two groups, each group was told a different version of a story.

Procedure: Group 1 was told a mundane story about a child and their mother visiting the father in a hospital during a routine nurse training exercise, designed to be uneventful and thus less memorable. Group 2 heard a more emotionally charged story involving a child whose legs were severed in a car accident but were surgically reattached at the hospital. Two weeks later, all participants were given a multiple-choice recognition test to assess how well they remembered the story details.

Findings: The study found that participants who heard the more emotionally intense story (Group 2) had better recall on the recognition test compared to those who heard the less interesting story (Group 1). This suggests that emotional arousal, potentially involving adrenaline’s effects on the amygdala, enhances the formation and retention of memories.

A follow-up study was made where all the participants came back and got told the same story yet this time the ones that heard the traumatic one got injected with beta-blocker propranolol (stops production of adrenaline)

After performing the recognition test again after two weeks, results show that they performed worse than they did the first time

Question 16

Pheromones and Behavior

Answer 16

Pheromones - They’re chemical substances secreted externally to another individual in order to induce a specific reaction
Attraction - The action of evoking interest, pleasure, or liking for someone
Androstadienone - This is a pheromone theorized to be excreted by women to attract men
Major Histocompatibility Complex (MHC) - This is an individual’s immune system
This is not a pheromone, however it’s theorized that men sweat a pheromone that allows females to know which MHC opposes their own, inducing attraction

When doing the “to what extent”:
It’s important to use Doty (2010) as a supporting study while still putting emphasis to the other studies limitations
Studies: Saxton et al. (2008) Androstadienone and Wedekind et al. (1995) Major Histocompatibility complex

Question 17

Saxton et al. (2008)

Answer 17

Aim: To investigate the influence of androstadienone on sexual attraction during speed dating events.

Participants: 47 participants, including 22 males and 25 females, participated in the speed dating study.

Procedure: Field study. During the speed dating events, female participants had cotton wool pads under their noses, with three conditions applied: androstadienone mixed with clove oil, clove oil alone, or plain water.

Findings: The study found that women exposed to androstadienone rated male participants as more attractive compared to those exposed to clove oil or water, suggesting that androstadienone may enhance perceptions of male attractiveness during initial encounters​.
Ethics: deception

Question 18

Wedekind et al. (1995) MHC

Answer 18

Aim: To examine whether the Major Histocompatibility Complex (MHC) influences human mate selection based on scent.

Participants: The study involved 49 female and 44 male students who were tested for their MHC through blood sampling.

Procedure: Quasi Exp. Male participants wore a T-shirt for two nights during which they were to avoid certain foods and activities that could alter their natural scent. Subsequently, their MHC genes were tested through blood samples. Women then sniffed these T-shirts and rated the scents for attractiveness.

Findings: Women preferred the scent of T-shirts worn by men with dissimilar MHC genes to their own, suggesting that MHC may play a role in mate selection by influencing scent preferences.

Question 19

Evolution

Answer 19

Evolutionary Approach - Psychologists believe that if a behavior persists to this day then it must be a useful adaptation that helps humans reproduce in order for the species to survive
Disgust - A feeling of revulsion aroused by something unpleasant
Successful Reproduction - Based on evolutionary perspectives, disgust is a key behavior for the reproductive success of humans
Survival of Diseases - Based on evolutionary perspectives, disgust is a key behavior for the survival of humans
Studies: Curtis et al. (2004) and Fessler et al. (2006)

Question 20

Curtis et al. (2004)

Answer 20

Aim: The study aimed to test the hypothesis that the emotion of disgust has evolved to protect humans from the risk of disease but also in reproduction

Participants: The study utilized an international sample, drawing responses from over 77,000 people from 165 countries via an online survey hosted on the BBC Science website.

Procedure: Participants were asked to rate their level of disgust for 20 photographs, each displayed on separate web pages. These photos included seven pairs, each pair containing one disease-salient image and another image that was similar but lacked disease relevance. Additionally, a final question inquired which person among a list they would least like to share a toothbrush with.

Findings: The results indicated that disease-salient images were rated as more disgusting compared to their non-disease counterparts. Women rated these images as more disgusting than men did, which the researchers suggest could be linked to an evolutionary role in protecting offspring from pathogens. The study also found that disgust reactions decrease with age, and people were least willing to share a toothbrush with strangers, indicating an evolutionary mechanism favoring familiar individuals to avoid new diseases.

These results support the theory that disgust functions as a protective mechanism against diseases, likely contributing to survival and reproductive success by avoiding pathogens. The study was extensive and cross-cultural, though it had limitations in demographic representation and a higher response rate from Europe, particularly the UK. This research provides robust evidence supporting the role of disgust in evolutionary psychology and disease avoidance

Question 21

Fessler et al. (2006) - Disgust

Answer 21

Aim: To investigate if heightened disgust sensitivity in pregnant women during the first trimester is an evolutionary adaptation to protect against pathogens at a time when immunosuppression is increased.

Participants: The study involved 496 healthy pregnant women between the ages of 18 and 50.

Procedure: The women were asked to rank their level of disgust for 32 scenarios that could potentially involve pathogen transmission, focusing particularly on food-related scenarios. This survey was conducted to see if heightened disgust serves to compensate for the lowered immune system during early pregnancy.

Findings: Results showed that disgust sensitivity was significantly higher in the first trimester compared to later stages of pregnancy. When controlled for morning sickness, the heightened disgust was particularly associated with food-related scenarios. This supports the hypothesis that increased disgust sensitivity in early pregnancy is an adaptive response to protect against disease when the immune system is suppressed.

The study suggests that evolutionary pressures have shaped psychological mechanisms that enhance disease avoidance behaviors during critical periods of pregnancy.

Question 22

Role of Genes

Answer 22

Genetics - Theory that assumes behavior comes from our innate “code”
Family Study - A way to study how genetic similarities affect behavior as seen through comparisons between generations
Adoption Study - A way to study how genetic similarities and the environment affects behavior as seen through comparisons between the biological mother and the adopter
Twin Study - A way to study how genetic similarities affect behavior as seen through comparisons between monozygotic and dizygotic twins
Concordance rates are percentages that show how many twins share the behavior under observation
Anti-Social Behavior - Refers to actions that violate social norms in ways that reflect disregard for others.
Studies: Brunner et al. (1993) Family study and Christansen (1977) twin study and Mednick et al. (1984)
Bandura (1961) - The environment has an effect on antisocial behavior, as demonstrated with the bobo doll study. Results showed that children behaved as the model did. Showing that the environment plays an important role too

Question 23

Brunner et al. (1993) - Family Study

Answer 23

Aim: To demonstrate the presence of a specific gene linked to antisocial behavior in a Dutch family.

Participants: The study involved members of a large Dutch family, many of whom had a history of antisocial behavior.

Procedure: Method Triangulation of case study. The researchers conducted genetic analyses on the family members. They particularly focused on identifying mutations or abnormalities in the MAOA gene, which is involved in the metabolism of neurotransmitters in the brain such as serotonin and dopamine.

Findings: Brunner et al. found a mutation in the MAOA gene that appeared to be associated with the violent and impulsive behaviors exhibited by the affected male members of the family. This mutation was associated with a deficiency in the enzyme monoamine oxidase A (MAOA), leading to abnormal neurotransmitter activity. The study concluded that this genetic defect could be linked to the increased likelihood of exhibiting aggressive and antisocial behavior.

This study was one of the first to suggest a direct genetic link to aggressive behavior, contributing significantly to the fields of genetics and behavioral science by highlighting the potential influence of genetics on behavior.

Question 24

Christiansen (1997) Twin study

Answer 24

antisocial behavior= criminal behavior
Aim: To assess the influence of hereditary factors on antisocial behavior by comparing concordance rates for antisocial behavior between monozygotic (MZ) twins and dizygotic (DZ) twins.

Participants: The study included 3,500 twins from Denmark, encompassing both monozygotic twins, who share 100% of their genes, and dizygotic twins, who share approximately 50% of their genes.

Procedure: Christiansen collected data on the criminal records of the twins and determined whether each twin pair was MZ or DZ through blood tests. The main measure was whether both twins in a pair exhibited antisocial behavior (concordance for antisocial behavior).

Findings: The results showed higher concordance rates for antisocial behavior among monozygotic twins compared to dizygotic twins. Specifically, the concordance rate for antisocial behavior was 35% for MZ twins and 13% for DZ twins. This significant difference suggests that genetic factors play a role in antisocial behavior, although the environment also has a considerable impact, as indicated by the fact that not all MZ twins were concordant for antisocial behavior. The genotype isn’t specified.

This study, with its large sample size, provided robust evidence supporting the genetic influence on antisocial behavior, while also acknowledging the significant role of environmental factors.

Question 25

Mednick et al. (1984) adoption study

Answer 25

Aim: To investigate whether adopted individuals with biological parents who had criminal records were more likely to engage in criminal activity, and how this propensity was affected by the criminality of their adoptive parents.

Participants: The study analyzed data from 14,427 adoptions that took place in Denmark, using official records to examine the criminal histories of the biological and adoptive parents as well as the adoptees themselves.

Procedure: Mednick and his team accessed Danish adoption records, gathering information on the criminal history of adoptees and their biological and adoptive parents. They then examined the correlation between the criminal behavior of adoptees and their parents, looking to see if genetic factors or environmental influences were more predictive of criminal behavior in adoptees.

Findings: The study found that adoptees whose biological parents had criminal records were more likely to engage in criminal behavior themselves, particularly if their adoptive parents also had criminal histories. This indicated a gene-environment interaction, where genetic predispositions for criminal behavior are more likely to manifest in environments conducive to such behavior.

This study, with its extensive sample size, provided robust evidence of the complex interactions between genetic predispositions and environmental factors in the development of criminal behavior, demonstrating that both nature and nurture significantly influence criminal outcomes.

Question 26

Animal Research- Brain and Behavior

Answer 26

Prevot et al. (2019) - agonist and inhibitory: Mice, Y maze and imidazobenzodiazepine (agonist)
Ethics
Replace- Justifiable as rats are similar to humans’ brain, and they are getting administered a powerful drug

Reduce- The sample of the mice is unknown

Refine- Mice were sacrificed, not ethical

Rosenzweig et al. (1972)

Aim: To determine how different environmental complexities affect the neuroplasticity of the brain, specifically examining changes in cortical thickness and synaptic connections.

Participants: The subjects of the study were laboratory rats, which were divided into three groups based on the type of environment they were exposed to: enriched environment (EE), standard environment (SE), and impoverished environment (IE).

Procedure: The rats were placed in one of the three environments for a specified period:
Enriched Environment (EE): Rats were housed in groups with various toys and exercise equipment, which were changed regularly to provide new stimuli.
Standard Environment (SE): Rats were housed in pairs with sufficient food and water but no additional stimuli.
Impoverished Environment (IE): Rats were housed individually in small, bare cages without stimuli.

After the experimental period, the rats were euthanized, and their brains were examined to measure physical differences in brain structure, particularly in the cerebral cortex.

Findings: The study found significant differences in brain structure among the three groups. Rats in the enriched environment showed an increase in cortical thickness and greater synaptic connections compared to those in standard and impoverished environments. These changes indicated that the brain’s structure and function could be significantly influenced by environmental factors, suggesting that neuroplasticity is responsive to the richness of the environment.

Ethics
Replace- Human research could’ve been done as seen with Luby’s study

Reduce- They used a very small number of mice

Refine- Mice were sacrificed, not ethical. They were in an impoverished environment too

Question 27

Animal Research- Hormones and Behavior

Answer 27

Berthold (1849) - Removing Testes
Aim: To determine the effects of castration and the transplantation of testes on the physiology and behavior of roosters.

Participants: The subjects of the study were domestic roosters.

Procedure: Berthold’s experiment involved several key steps:

Castration: Several roosters were castrated to remove their testes, allowing Berthold to observe any subsequent changes in their physical traits and behaviors.
Transplantation: In some of the castrated roosters, the testes were reimplanted into the abdominal cavity to see if the effects of castration could be reversed or mitigated.
Control Group: Some roosters were not castrated and served as a control group to provide baseline observations of normal rooster behavior and physical development.
Findings: Berthold’s findings were pioneering for several reasons:

Castrated Roosters: Those without testes showed reduced secondary sexual characteristics, such as smaller combs and wattles, less aggressive and territorial behavior, and no interest in hens.
Transplanted Roosters: Roosters with reimplanted testes largely regained their normal sexual behaviors and developed typical physical secondary characteristics, comparable to those in the control group.
Berthold concluded that the testes produce a substance that circulated through the bloodstream, influencing sexual development and behavior.

Delville (2004) - bullying and cortisol
Aim: To explore how being subjected to bullying affects cortisol levels, which are indicators of stress, in young hamsters.

Participants: The subjects of the study were juvenile hamsters.

Procedure: The study involved several key components:
- Exposure to Bullying: Juvenile hamsters were exposed to older, more aggressive hamsters that acted as “bullies.” The interactions were controlled to ensure the young hamsters experienced intimidation without physical harm.
- Cortisol Measurement: The cortisol levels of the young hamsters were measured before and after the bullying sessions to assess changes in their stress hormone levels.
- Behavioral Observations: The behavior of the young hamsters was also monitored to document changes in social interactions and signs of stress or anxiety, such as decreased social engagement or changes in grooming habits.

Findings: The study found that juvenile hamsters subjected to bullying showed significant increases in cortisol levels, indicating elevated stress. Additionally, these hamsters displayed behavioral changes that included more submissive postures and reduced social interaction, suggesting that the social stress had a profound effect on both their physiological state and behavior. This research has implications for understanding how social stressors during critical development periods can influence psychological and physiological development in humans as well.

Question 28

Animal Research- Role of Genes

Answer 28

Weaver et al. (2004) - epigenetics on maternal rats

Aim: To investigate whether different levels of maternal care affect stress levels in rat offspring, measured through changes in behavior and physiological stress markers.

Sampling: The study involved two groups of rat offspring:
Offspring with calmer, more nurturing mothers.
Offspring with more anxious, less attentive mothers.

Procedure:
Stress Measurement: Stress levels in the rats were assessed by placing each rat in a confined tube for 20 minutes and subsequently measuring the levels of corticosterone, a stress hormone.
Cross-fostering Experiment:
The first group comprised rats that initially received less attention but were then exposed to vigorous licking and grooming from other rats.
The second group included rats that initially received significant maternal care but were later given less attention.

Findings:
1st Experiment: Rats raised by calmer and more nurturing mothers exhibited lower stress levels compared to those raised by more anxious and less attentive mothers.
2nd Experiment: The study demonstrated that environmental factors, not just genetic inheritance, significantly influence behavior and gene expression. Changes in the nurturing environment altered stress hormone levels, indicating that gene expression related to stress responses can be modulated by environmental conditions.

Conclusion:
Weaver et al. concluded that while genetic inheritance plays a crucial role in behavior, the environment also has a profound impact on gene expression and behavior. This study highlighted the dynamic interplay between genetics and environmental factors in shaping physiological and behavioral outcomes, particularly in how stress responses are developed and managed. This research adds to the understanding of epigenetics, showing that environmental changes can alter gene expression in ways that affect an organism’s stress management and overall behavior.

Cases et al. (1995) - origins of aggression

Aim: to explore the role of the MAOA gene in regulating aggressive behavior by examining genetically modified mice.

Participants: The study involved mice genetically engineered to lack the MAOA gene, referred to as MAOA knockout mice.

Procedure: The researchers genetically altered mice to disable the MAOA gene, which is crucial for breaking down neurotransmitters like serotonin. They compared the behavior and neurotransmitter levels of these knockout mice with control mice possessing a functional MAOA gene.

Findings: MAOA knockout mice exhibited significantly more aggressive behavior and had elevated levels of serotonin and other neurotransmitters in the brain compared to control mice. This study highlighted the essential role of the MAOA gene in aggression and mood regulation.