Biological Approach

Aim: (Maguire et al 2000)

To investigate the correlation between spatial memory and the size and density of neural networks in the hippocampus, specifically focusing on the ability of the brain to change in volume of grey matter based on learning and experience.

Participants: (Maguire et al 2000)

• 16 healthy, right-handed male licensed London taxi drivers.

• Age range: 32 to 62 years, with a mean age of 44.

• All participants had been taxi drivers for a minimum of 18 months, with the most experienced driver having 42 years of experience.

Method: (Maguire et al 2000)

A quasi-experimental design utilizing MRI scans to measure the volume of grey matter in the hippocampus.

Procedure: (Maguire et al 2000)

1. Participants underwent MRI scans to assess the volume of grey matter in their hippocampus.

2. The grey matter was measured using voxel-based morphometry (VBM), which focuses on density and pixel counting.

3. The MRI scans of the taxi drivers were compared to pre-existing scans of 50 healthy right-handed males who were not taxi drivers (control group).

Results: (Maguire et al 2000)

• The posterior hippocampi, particularly the right side, of taxi drivers showed a greater volume of grey matter compared to the control group, who had increased grey matter in their anterior hippocampi.

• A significant positive correlation was found between the growth of the right posterior hippocampal neural networks and the length of time spent as a taxi driver.

Conclusion: (Maguire et al 2000)

The findings suggest that the posterior hippocampus is linked to spatial navigation skills developed through learning and experience. The correlation between the time spent as a taxi driver and the increased volume of hippocampal grey matter supports the concept of neuroplasticity, countering the argument that the observed larger hippocampi were merely coincidental.

Aim: (Draganski et al. 2004)

To determine whether learning a new motor skill (juggling) would result in both structural and functional changes in the brain.

Participants: (Draganski et al. 2004)

The participants for this study were 24 volunteers between the ages of 20 and 24. There were 21 females and 3 males. All participants were non-jugglers at the start of the study.

Method: (Draganski et al. 2004)

A field experiment utilizing MRI scans to observe changes in brain structure related to learning to juggle.

Procedure: (Draganski et al. 2004)

1. Participants were randomly allocated to two groups: Juggling group and Non-juggling (control) group

2. Participants' brains were scanned three times: - Before learning to juggle (baseline scan). - After three months of practicing juggling. - Three months after ceasing juggling.

3. The brain scans of jugglers were compared to those of the non-juggling control group.

Results: (Draganski et al. 2004)

• No differences in brain structure were observed between the two groups in the first scan.

• In the second scan (after three months), jugglers exhibited significant differences in size in two specific areas of the brain compared to the control group.

• These differences diminished in the third scan (three months after stopping juggling), indicating a reduction in structural changes.

Conclusion: (Draganski et al. 2004)

The study concluded that the process of learning to juggle and the related visual and motor coordination strengthened neuronal connections in specific brain areas. However, these changes were temporary and dependent on continued practice; without ongoing juggling, neural pruning occurred as the connections were no longer used. Despite being a field experiment, the study maintained high internal validity due to random allocation and standardized measurements.

Aim: (Antonova et al. 2011)

To investigate the role of the neurotransmitter acetylcholine (ACh) in spatial memory by assessing the effects of scopolamine on brain activity and performance in a virtual reality maze.

Participants: (Antonova et al. 2011)

• 20 male participants with an average age of 28 years.

• Participants were randomly assigned to either a scopolamine injection group or a saline injection (placebo/control) group.

Method: (Antonova et al. 2011)

A randomized double-blind cross-over design was used, allowing for comparisons between the effects of scopolamine and placebo within the same participants.

Procedure: (Antonova et al. 2011)

1. Participants completed a trial in a virtual reality maze while receiving either a scopolamine injection or a saline injection.

2. Their brains were scanned using functional magnetic resonance imaging (fMRI) during the maze task.

3. After one trial, participants returned 3-4 weeks later, received the alternate injection, and were scanned again.

4. The study ensured that neither the participants nor the researchers knew who received which injection during the trials.

Results: (Antonova et al. 2011)

• Scopolamine reduced activity in the hippocampal area.

• Participants who received scopolamine made more errors in the maze task compared to those who received the placebo.

Conclusion: (Antonova et al. 2011)

The findings confirm that scopolamine decreases the action of ACh in the brain, which is associated with spatial memory in adults, similar to previous findings in non-human animals.

Aim: (Martinez and Kesner, 1991)

To investigate the role of the neurotransmitter acetylcholine (ACh) in the formation of spatial memory.

Participants: (Martinez and Kesner, 1991)

Laboratory rats that were trained to navigate a maze.

Method: (Martinez and Kesner, 1991)

Experimental design involving three groups of rats, each receiving different treatments affecting ACh levels.

Procedure: (Martinez and Kesner, 1991)

1. Rats were trained to run a maze.

2. The rats were divided into three groups:

• Group 1: Injected with scopolamine, which blocks ACh receptor sites, reducing ACh availability.

• Group 2: Injected with physostigmine, which inhibits cholinesterase and increases ACh availability.

• Group 3: Control group that received no injections.

3. The performance of each group was assessed based on the time taken to complete the maze and the number of mistakes made.

Results: (Martinez and Kesner, 1991)

• Group 1 (scopolamine) made more mistakes and were slower in navigating the maze compared to both Group 2 (physostigmine) and the control group.

• Group 2 (physostigmine) ran through the maze more quickly and made fewer mistakes than both the control group and Group 1.

Conclusion: (Martinez and Kesner, 1991)

The study concluded that ACh is a key neurotransmitter that enhances spatial memory, as indicated by the performance differences among the groups based on ACh availability.

Aim: (Nave et al. 2017)

To investigate the effect of testosterone on cognitive reflection in males, specifically examining whether testosterone reduces cognitive reflection.

Participants: (Nave et al. 2017)

243 healthy male participants.

Method: (Nave et al. 2017)

A randomized controlled trial where participants received either testosterone or a placebo.

Procedure: (Nave et al. 2017)

1. Participants provided a baseline saliva sample to measure testosterone levels.

2. They were randomly assigned to receive either a single dose of testosterone gel or a placebo gel applied to the skin.

3. After a few hours, participants returned to provide a follow-up saliva sample to confirm hormone levels.

4. All participants completed the Cognitive Reflection Test (CRT), which assesses the ability to override impulsive judgments with deliberate responses.

5. Saliva samples were collected during the testing and at the end of the test.

Results: (Nave et al. 2017)

Participants who received testosterone had significantly lower scores on the Cognitive Reflection Test compared to the control group, indicating a reduction in cognitive reflection.

Conclusion: (Nave et al. 2017)

The findings demonstrate a clear effect of testosterone on cognition and decision-making, suggesting that higher testosterone levels may impair cognitive reflection in males. Further research is needed to determine if similar effects occur in females.

Aim: (Carré et al. 2016)

To determine whether aspects of personality affect aggressive responses to a game, in the context of the inconsistent findings related to aggression and testosterone levels.

Participants: (Carré et al. 2016)

121 healthy male participants.

Method: (Carré et al. 2016)

A double-blind experimental design where participants were randomly allocated to two groups: one receiving a placebo and the other receiving an injection of testosterone.

Procedure: (Carré et al. 2016)

1. Participants were injected with either testosterone or a placebo, with neither the experimenters nor the participants aware of which injection was given.

2. After the injection, all participants underwent a decision-making game designed to assess aggression following social provocation by a partner (actually a computer).

3. Personality traits related to dominance and impulsivity were measured using questionnaires.

Results: (Carré et al. 2016)

• An increase in testosterone levels alone did not provoke aggression.

• Higher aggression was observed only in men who received testosterone and scored high in dominance while scoring low in impulse control, compared to the control group and testosterone group without these traits.

Conclusion: (Carré et al. 2016)

The findings suggest that personality traits, specifically high dominance and low impulse control, interact with elevated testosterone levels to influence aggressive behavior, indicating that testosterone's effects on aggression are not straightforward and depend on individual personality characteristics.

Aim: (Wedekind et al. 1995)

To investigate whether females prefer male odours from males with a different major histocompatibility complex (MHC) from their own, suggesting an influence of pheromones on human attraction.

Participants: (Wedekind et al. 1995)

• 44 male students with a mean age of 25 years. - 49 female students who rated the T-shirts.

Method: (Wedekind et al. 1995)

Experimental design assessing the relationship between MHC similarity and female odour preference.

Procedure: (Wedekind et al. 1995)

1. Male participants wore the same T-shirt for two consecutive nights while maintaining odour neutrality.

2. The T-shirts were kept in plastic bags between wearings. 3. Male participants were classified by immune system similarity via blood tests prior to the study.

3. The day after wearing the T-shirts, female participants rated six T-shirts (three from males with similar MHC and three from males with different MHC) for pleasantness and odour intensity using a triangular hole in a cardboard box.

Results: (Wedekind et al. 1995)

• Females found the body odour of males with a different MHC more pleasant than that of males with a similar MHC.

• Women on the oral contraceptive pill showed a preference for males with similar MHC, suggesting a shift in mate preference due to hormonal influences.

Conclusion: (Wedekind et al. 1995)

The study concluded that MHC dissimilarity plays a role in female attraction to male odours, but the use of contraceptive pills may interfere with natural mate choice based on MHC dissimilarity, potentially reflecting a hormonally-induced shift toward kin association for childcare support.

Aim: (Doty 2010)

To dispute the existence of human pheromones that are detectable by other humans and challenge the claims made by other researchers about their role in human behavior.

Method: (Doty 2010)

A review and critique of existing literature on human pheromones and their proposed effects on behavior, including mate selection and emotional responses.

Procedure: (Doty 2010)

1. Doty discusses the lack of a scientific definition for what constitutes a mammalian pheromone.

2. He examines the claim that human pheromones have not been chemically isolated despite assertions of their significance.

3. Doty critiques the tendency to extrapolate findings from insect pheromone research to humans, highlighting potential dangers in doing so.

Results: (Doty 2010)

Doty concludes that human pheromones, as traditionally understood, have not been chemically proven to exist, and that behavioral changes cannot be attributed to a single chemical due to the complex nature of environmental influences.

Conclusion: (Doty 2010)

The arguments presented suggest skepticism regarding the idea that humans emit pheromones capable of influencing behavior, emphasizing the need for clearer definitions and more rigorous scientific evidence in this area of research.

Aim: (Suderman et al. 2014)

To investigate the relationship between childhood abuse and DNA methylation, particularly focusing on the gene PM20D1, and how these factors may affect eating habits and long-term health outcomes.

Participants: (Suderman et al. 2014)

• 12 adults who had suffered childhood abuse.

• A control group of 28 adults who had not suffered such abuse.

• All participants were 45-year-old males.

Method: (Suderman et al. 2014)

Analysis of blood DNA to assess methylation levels.

Procedure: (Suderman et al. 2014)

1. Blood samples were collected from both groups of participants.

2. DNA methylation of the gene PM20D1 was specifically analyzed to determine differences between the abused group and the control group.

Results: (Suderman et al. 2014)

• Participants who had suffered childhood abuse showed increased methylation of the PM20D1 gene compared to the control group.

• The study linked increased methylation to a greater prevalence of obesity among those reporting physical abuse in childhood, supporting previous research on this gene's association with childhood abuse and adult obesity

Conclusion: (Suderman et al. 2014)

The findings suggest that environmental triggers like childhood abuse can lead to changes in gene expression through DNA methylation, specifically affecting genes associated with metabolism and eating habits. This indicates a correlation between gene PM20D1 methylation, childhood abuse, and the predisposition to certain behaviors related to food intake, emphasizing the interaction between genetics and environmental influences.

Aim: (Weaver et al. 2004)

To investigate the stress responses of rat pups based on the amount of maternal licking and grooming they received in the first ten days after birth.

Participants: (Weaver et al. 2004)

Rat pups that received varying levels of maternal attention from their mothers.

Method: (Weaver et al. 2004)

Measurement of stress responses by assessing corticosterone levels in rat pups placed in a confined situation.

Procedure: (Weaver et al. 2004)

1. Rat pups were placed into a small tube for twenty minutes to measure their stress responses.

2. The levels of the stress hormone corticosterone (a glucocorticoid) were measured in each rat.

3. A follow-up study was conducted where the offspring of anxious rats were raised by calmer mothers, and vice versa, to assess the influence of maternal behavior on stress reactivity.

Results: (Weaver et al. 2004)

• Rats that received more maternal attention had lower levels of corticosterone compared to those who did not receive much attention.

• The stress reactivity of the pups depended on the behavior of the adoptive mothers rather than their biological mothers.

Conclusion: (Weaver et al. 2004)

The study demonstrates that nurturing maternal behavior influences the stress responses of rat pups through epigenetic modifications, as shown by the methylation of glucocorticoid receptor genes in the brain. Pups raised by nurturing mothers exhibited less sensitivity to stress as adults, indicating that acquired epigenetic changes can be inherited and affect offspring, rather than being solely learned behavior.

Aim: (McGue et al. 2000)

To investigate the genetic and environmental influences on adolescent addiction to tobacco and marijuana.

Participants: (McGue et al. 2000)

• 626 pairs of male and female twins born in the same year.

• Males: 188 identical (monozygotic, MZ) twins and 101 non-identical (dizygotic, DZ) twins.

• Females: 223 MZ twins and 114 DZ twins.

Method: (McGue et al. 2000)

• Interviews conducted with twin pairs about their history and experience with legal (tobacco) and illegal (marijuana) drug use.

• Participants provided details about their home life and completed a questionnaire.

Procedure: (McGue et al. 2000)

1. Each twin pair was interviewed regarding their drug use and family environment.

2. Data on tobacco and marijuana use was collected and analyzed to determine heritability and the influence of shared environment.

Results: (McGue et al. 2000)

• Heritability for marijuana use was found to be between 10% - 25%, with no significant differences between males and females.

• Heritability for tobacco use showed a higher range of 40% - 60%.

• A significant finding was the influence of shared environment, as participants with a history of drug use reported that drugs were a regular part of family life.

Conclusion: (McGue et al. 2000)

The study concluded that environmental factors appear to have a more substantial influence on drug use among adolescents than genetic inheritance, highlighting the importance of the home environment in shaping attitudes towards drug use.

Aim: (Kendler et al. 2006)

To investigate the heritability of major depressive disorder (MDD) using a large Swedish twin study.

Participants: (Kendler et al. 2006)

15,493 complete twin pairs listed in the national twin registry

Method: (Kendler et al. 2006)

Telephone interviews conducted over a period of 4 years to diagnose MDD based on DSM-IV symptoms or prescription history for antidepressants.

Procedure: (Kendler et al. 2006)

1. Twins were assessed for the presence of MDD symptoms through structured interviews.

2. Diagnosis was made based on either reported symptoms or evidence of antidepressant prescriptions.

3. Concordance rates for MDD were calculated for both monozygotic (MZ) and dizygotic (DZ) twins.

Results: (Kendler et al. 2006)

• The average concordance rate for MDD among all twins was found to be 38%.

• Female MZ twins had a concordance rate of 44%, while male MZ twins had a rate of 31%.

• In contrast, DZ twins showed lower concordance rates of 16% for females and 11% for males.

• There was no correlation between the number of years twins lived together and the incidence of MDD, supporting a heritable component.

Conclusion: (Kendler et al. 2006)

The study concluded that there is a significant genetic component to the heritability of MDD, particularly higher in women than in men. The findings also suggest that some genetic risk factors for MDD may be sex-specific, as evidenced by the differences in concordance rates between male and female twins.

Aim: (Curtis et al. 2004)

To investigate the role of disgust as an evolutionary mechanism for detecting disease and its influence on human behavior.

Participants: (Curtis et al. 2004)

• Over 40,000 people completed the survey.

• The majority of participants were from Europe, with some from the Americas, Asia, Oceania, and Africa.

• 75% of participants were aged between 17 and 45 years old.

Method: (Curtis et al. 2004)

A survey was added to the BBC Science website after a documentary on instinctive human behavior, in which participants rated photographs for disgust.

Procedure: (Curtis et al. 2004)

1. Participants viewed twenty photographs that depicted various objects and scenarios.

2. They rated each photograph on a Likert scale of 1-5, indicating the level of disgust elicited.

3. A final question asked participants to select whom they would least like to share a toothbrush with, providing options including a postman, boss, weatherman, sibling, best friend, and spouse/partner.

Results: (Curtis et al. 2004)

• Photographs representing a threat of disease were rated as more disgusting.

• The postman was the least acceptable person to share a toothbrush with (59.3%), followed by the boss (24.7%), weatherman (8.9%), sibling (3.3%), best friend (1.9%), and spouse/partner (1.8%).

• The study indicated that sharing bodily fluids was deemed more disgusting with less familiar individuals due to perceived disease threats.

Conclusion: (Curtis et al. 2004)

The findings support the notion that disgust serves as an evolutionary mechanism for detecting disease, highlighting its role in human survival by promoting avoidance behaviors towards potential sources of infection.

Aim: (Buss et al. 1992)

To investigate the differences between men and women regarding sexual selection, specifically in their reactions to sexual and emotional infidelity.

Participants: (Buss et al. 1992)

202 undergraduate students (opportunity sample).

Method: (Buss et al. 1992)

• Participants were asked to imagine scenarios involving sexual or emotional infidelity by their partner.

• Their distress was assessed through various measures of emotional and physiological arousal.

Procedure: (Buss et al. 1992)

1. Participants vividly imagined scenarios where their partner engaged in either sexual or emotional infidelity.

2. Emotional arousal was measured through questionnaires, while physiological arousal was assessed through indicators like sweat response.

Results: (Buss et al. 1992)

• Sexual infidelity caused significantly more distress in males.

• Emotional infidelity elicited more distress in females.

• These findings align with predictions from evolutionary psychology.

Conclusion: (Buss et al. 1992)

The study concluded that men are primarily concerned about paternity uncertainty, fearing their sperm may be replaced, while women are more worried about their partners developing emotional attachments, which could jeopardize resource allocation. This illustrates the differing concerns between males and females regarding sexual selection, consistent with evolutionary theory.

Aim: (Albert et al. 1986)

To investigate the effect of testosterone on aggression in male rats.

Participants: (Albert et al. 1986)

Male rats, specifically focusing on identifying alpha males (dominant males) based on their size and strength.

Method: (Albert et al. 1986)

Measurement of aggression levels through behavioral observations when non-aggressive rats were placed in the same cage as alpha males.

Procedure: (Albert et al. 1986)

1. Alpha male rats were identified and placed in cages with non-aggressive rats.

2. Aggression levels were measured based on behaviors such as attacking and biting.

3. The alpha males were randomly divided into four groups for surgical interventions:

• Group 1: Castration.

• Group 2: Castration followed by the implantation of empty tubes.

• Group 3: Castration followed by the implantation of tubes with testosterone.

• Group 4: Sham castration followed by the implantation of empty tubes.

4. Aggression levels were reassessed after reintroducing non-aggressive rats.

Results: (Albert et al. 1986)

• Groups 1 and 2 (testosterone-reducing operations) exhibited decreased aggression.

• Groups 3 and 4 (testosterone-intact operations) showed no significant change in aggression levels.

• After replacing testosterone in Group 2, aggression levels returned to those similar to Groups 3 and 4.

• The dominance of a previously non-aggressive male was observed when placed with a castrated alpha rat, indicating that social dynamics changed based on testosterone levels.

Conclusion: (Albert et al. 1986)

The study concluded that testosterone facilitates behaviors associated with social dominance and aggression in male rats. The manipulation of testosterone levels demonstrated a clear relationship between testosterone and aggressive behavior, supporting the idea that higher testosterone levels contribute to increased aggression and dominance.

Localization

the theory that the mechanisms for thought, behaviour and emotions are located in different areas of the brain. To what extent certain functions are located in their own areas, and activity in this area can therefore be seen as evidence of a behaviour, thought or feeling, is the subject of localization of brain function.

neuroplasticity

that complex neural networks can also be modified and changed

neural pruning

reduction in density of neural networks as some neural pathways in the brain are no longer needed

Neurotransmission

Neurons carry information as electrical impulses but neurons communicate with each other by an additional chemical process involving neurotransmitters These are chemicals that are released across a gap between the neurons called the synapse and the neurotransmitter is then picked up by the receptors of another neuron.

Neuron

Single Nerve Cell

postsynaptic potential (PSP)

When the neurotransmitter combines with a molecule at the receptor site it causes a voltage change at the receptor site

excitatory synapse

increases the probability of producing an action potential in the receiving neuron

inhibitory synapse

decreases the probability of producing an action potential.

Agonists

All neurotransmitters are natural agonists that are endogenous (produced by the body and act inside the body). They bind to synaptic receptor neurons to generate either an excitatory or inhibitory PSP. Chemical agonists are substances that bind to synaptic receptors and increase the effect of the neurotransmitter. They do this by imitating the neurotransmitter. Lock and Key Mechanism

Antagonists

Antagonists are chemical substances, both naturally found in food, and medicines, and artificially manufactured. They also bind to synaptic receptors but they decrease the effect of the neurotransmitter. Chewing Gum in Lock

Hormones

chemical messengers that are secreted (secrete = given out) by glands and enter directly into the bloodstream