Biological Approach studies

Aim (Antonova)

To see if scopolamine affects hippocampal activity in the creation of spatial memory

Procedure (Antonova)

Twenty healthy male adults (mean age 28) were randomly allocated to receive either a scopolamine or placebo injection 70-90 minutes before the experimental task. The participants were trained to play the “arena task”, which allows for the observation of the creation of spatial memories. Participants navigate around an arena to find a pole, then the screen goes blank and they are given 30 seconds to mentally rehearse how to find the pole. Then the arena reappears with the participant in a new starting position from which they need to find the pole again using spatial memory. Once they understood how to play and operate the game, the brain activity of the participants was measured in an fMRI for 6 trials. The participants repeated the experiment in the opposite condition 3-4 weeks later.

Results (Antonova)

Participants injected with scopolamine had significantly less activation in the hippocampus than those that had received the placebo. This demonstrates that acetylcholine may play a role in the creation of spatial memory.

Evaluation (Antonova)

Strengths:

• Repeated measures (eliminates participant variability)

• Counter-balanced (controls for practice effect)

• Double blind (controls for researcher bias)

Limitations:

• Although there was a significant difference in hippocampal activity, the rate of error wasn’t that much lower for the scopolamine group than the placebo group (no difference would have been able to be seen without an fMRI)

• Participants reported feeling stressed either because of the injection or the fMRI, which could impact the hippocampus since stress is related to memory formation

• Small sample size (results need to be replicated for reliability)

Background (The case of EP)

EP sustained cognitive impairment, including large lesions in the medial temporal lobe, after a case of viral encephalitis. He was unable to form new declarative memories but recall most prior events and was still socially functional. He was unable to draw a map of his home but was able to navigate it on his own.

Aim (The case of EP)

To determine the reason behind EP’s behavior

Procedure (The case of EP)

This case study involved interviews with EP and his family, psychometric testing, observations (such as problem solving or memory tasks), and MRIs. An autobiographical memory interview (AMI) was conducted in which EP was asked to recall personal semantic knowledge and autobiographical knowledge from his childhood, early adult life, and recent life. At least two family members verified each of his responses. The case study also involved an experiment in which 16 different objects were paired and glued to cardboard pieces. On one of each of the pairs the word correct was written, and EP had to choose the correct one between the two. The experiment was conducted twice a week for many months, with 40 pairings being done each time.

Results (The case of EP)

EP was unable to describe how he traveled from his home to other locations, did not have any impairment of intelligence, could not remember a string of numbers, and had the most damage in the anterior temporal lobe, which includes the amygdala and hippocampus. For the AMI, EP performed very poorly in remembering recent life events, and better but still below the control scores for early adult events. However, he performed normally when remembering childhood events. For the object experiment, he chose the correct object 85% of the time after 28 days and 95% of the time after 36 days. He would also turn over the objects without instruction, even though he didn’t remember that there was something on the bottom. EP was later asked to put all the correct objects in a pile, but he was only able to pick the correct object from consistent pairings. EP’s basal ganglia was undamaged, and a prior study in rats had shown that damage to the basal ganglia made it difficult for them to learn how to run a maze, so researchers concluded that the basal ganglia is responsible for procedural memory.

Evaluation (The case of EP)

Strengths:

• Results show that memory is more complex than initially thought and not solely dependent on the hippocampus

Limitations:

• Habits need to be triggered with a cue 

• Generalizability is an issue since it is a case study

Aim (Draganski)

To see whether learning a new skill - in this case, juggling - would affect the brains of participants

Procedure (Draganski)

24 volunteers between the ages of 20 and 24 (21 females and 3 males) who did not know how to juggle first received an MRI scan as a baseline for gray matter and brain structure. They were split between the juggling and non-juggling conditions. The jugglers were taught a three ball cascade routine, then told to practice and notify a researcher when they had mastered it. At that point, they received a second MRI and told not to juggle anymore. They received a third MRI three months later.

Results (Draganski)

Using voxel-based morphometry, they determined that there was no significant difference in neural density between the two groups at the beginning of the experiment, but after the jugglers had mastered the skill they showed significantly more gray matter in the mid-temporal area in both hemispheres (associated with visual memory). Three months later the amount of gray matter in this area had decreased. The non-juggling participants showed no change over this time.

Evaluation (Draganski)

Strengths:

• Pretest/posttest design shows differences in neural density over time

• The experimental nature of the study allows for a cause and effect relation to be determined

• Included a control group

Limitations:

• Small sample size (results are potentially not reliable)

• Field experiment (issues with internal validity since most of the experiment took place in the homes of the participants)

Aim (Rosenzweig, Bennet, and Diamond)

To investigate whether environmental factors have an impact on neuron development in the cerebral cortex

Procedure (Rosenzweig, Bennet, and Diamond)

3 male rats from the same litter were randomly allocated to the control condition, impoverished condition, or enriched condition and spent 30-60 days there with access to food and water before they were killed to study changes in brain anatomy. The control condition had 3 rats, the impoverished condition was isolated, and the enriched condition had stimulus objects and 10-12 rats.

Results (Rosenzweig, Bennet, and Diamond)

The cerebral cortex was thicker and weighed more in rats in the enriched condition than the impoverished condition. Rats in the enriched condition had more activity in neurons in the cerebral cortex associated with acetylcholine transmission. Since animal and human brains are considered similar in regards to neuroplasticity, this study implies that the human brain can be changed by environmental stimulation.

*A follow-up experiment shows that the same results were achieved with just 30 minutes a day in the enriched condition

Evaluation (Rosenzweig, Bennet, and Diamond)

Strengths: 

• Highly controlled lab experiment, so cause and effect can be established. 

• The same results have been replicated many times

Limitations: 

• Unclear whether the independent variable was the toys or social stimulation (a follow-up study showed that rats didn’t play with the toys when isolated)

• Animal studies are difficult to generalize to humans

• Exercise could have made the difference in the enriched condition

• Rats were exposed to undue stress and harm (isolated and killed, should be shown that the results were worth the harm)

Aim (Caspi et al)

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

Procedure (Caspi et al)

The sample was made up of 847 New Zealand 26 year olds who had been assessed for mental health once every two years until they were 21. They were divided based on their 5-HTT alleles, with one group having two short, one group having two long, and one group having one of each. The mutation of this gene is the short allele, which about 43% of people have. Participants filled in a questionnaire about stressful life events regarding the frequency of 14 different events such as financial, employment, health, and relationship stressors between the ages of 21 and 26, and were assessed for depression.

Results (Caspi et al)

Participants with one or more short alleles showed more symptoms of depression and suicidal ideation in response to stressful life events, with the effect being strongest for those who had experienced more stressful life events. Researchers concluded that the gene itself does not lead to depression, but rather the interaction between the gene and stressful life events. A later study (Wilhelm et al) showed that 80% of participants with two short alleles became depressed after three or more stressful life events, while only 30% of participants with two long alleles developed depression in similar situations. More research is still needed to determine a clear relationship between a gene and depression.

Evaluation (Caspi et al)

Strengths:

• Provides a holistic argument (biological and environmental factors)

Limitations:

• Correlational (cause and effect cannot be determined) 

• Assumption that lack of serotonin causes depression

• Information about life events was self-reported (those who are less resilient are probably more likely to remember stressful life events)

• The results have not been replicated (low reliability)

• Some participants who did not carry the gene still became depressed (the gene alone therefore cannot cause depression)

Aim (Weissman et al)

To study the potential genetic nature of major depressive disorder

Procedure (Weissman et al)

This was a longitudinal pedigree study looking at 161 children, their parents, and their grandparents over the span of 20 years. The original depressed patients (the grandparents) were selected from a local outpatient clinic specialising in mood disorders, and the original non-depressed patients were selected from the same community. The parents and grandparents were interviewed four times during the experiment. The children were evaluated by a child psychiatrist and a psychologist, both of which were blind to past diagnoses or data collected in interviews.

Results (Weissman et al)

Children following two generations of major depressive disorder showed high rates of psychiatric disorders, with 59.2% of them showing signs of a disorder by 12 years old, most commonly anxiety. Children were at a higher risk for any disorder if both previous generations had depression than if their parents were not depressed, and the severity of depression correlated with a higher rate of mood disorders in their children. Children with depressed parents but not depressed grandparents were not significantly more at risk to develop depression.

Evaluation (Weissman et al)

Strengths:

• Longitudinal (reliability)

• Researcher triangulation (validity and reliability)

• Large sample size

Limitations:

• Time spent with healthy grandparents is a potential confounding variable

• No specific genotype is being studied

Aim (Wedekind)

To determine whether one's major histocompatibility complex (MHC) affects mate choice

Procedure (Wedekind)

The sample was made of students at the University of Bern, Switzerland, and each participant was “typed” for their MHC, with a wide variety being included in the sample. The women were taking biology or psychology courses and the men were taking chemistry, physics, or geography so that they likely didn’t know each other, and the women taking oral contraceptives were noted. The men were given a T-shirt to wear for two nights and place in an open plastic bag during the day. They were given perfume free detergent to wash clothes and soap for showering, and asked not to smoke tobacco, drink alcohol, eat spicy foods, or have sex. The women were asked to use a nose spray for two weeks leading up to the experiment to support the regeneration of the nasal mucous membrane and prevent colds, and were also given a copy of the novel Perfume to heighten their sense of smell. The women were asked to rank the smell of 7 of the T-shirts each placed in a cardboard box with a smelling hole, preferably within the second week after menstruation when their sense of smell is most sensitive. 3 of the boxes had shirts from men with similar MHC genes to the women, 3 had shirts from men with different MHC genes, and 1 was an unworn control. The shirts were ranked from 1-10 for intensity and pleasantness/sexiness, and the women were alone in the room where they smelled the shirts.

Results (Wedekind)

Women not taking oral contraceptives rated men with different MHC genes as having a more pleasant smell, and women taking oral contraceptives rated men with similar MHC genes as having a more pleasant smell, indicating that the MHC gene does impact mate choice.

Evaluation (Wedekind)

Strengths:

• The study has been replicated 

• Ability to detect MHC is important as studies have shown that couples with more similar MHCs are more likely to have miscarriages or children with a lower birth weight

• Double-blind (minimizes researcher bias and demand characteristics)

• Ethical standards met (informed consent and debriefing)

Limitations:

• Reductionist argument

• Not representative (similar age and culture)

Aim (Ronay and von Hippel)

To determine if men would take greater risks in the presence of an attractive female than in the presence of a male, and the role testosterone plays in this behavior

Procedure (Ronay and von Hippel)

The sample comprised 96 young adult male Australian skateboarders recruited at skateboard parks. Participants were allocated to either the male-researcher condition or the female-researcher condition. The participants were asked to do an easy trick and a difficult trick they could land about half the time, and did each trick 10 times. After taking a break, depending on the condition they were assigned to, they either did the tricks 10 more times in front of the same male researcher or a young, attractive female researcher who did not know the hypothesis. The attractiveness of the researcher was verified by having 20 men view photos of potential researchers. The attempts of the skateboarders were designated success, crash landing, or aborted attempt, with more aborted attempts being considered an indicator of low risk taking. Saliva samples were collected after the experiment to measure testosterone, and heart rate was measured before and during the experiment.

Results (Ronay and von Hippel)

The participants aborted tricks fewer times and had higher testosterone in the presence of a female researcher than a male researcher. Heart rate was not significantly different between the groups. This suggests that young men take more risks in the presence of an attractive woman and that testosterone may cause this; this makes sense from an evolutionary standpoint since risk taking shows strength and dominance.

Evaluation (Ronay and von Hippel)

Strengths:

• Attractiveness of the female researcher, time of day, and heart rate were all controlled

• Very natural conditions (high ecological validity)

Limitations:

• Repeated measures design means that order effects (fatigue or practice) could have influenced the results

• There was not a given standard of difficulty for the tricks (standardization)

• Aborted attempts were assumed indicators of low risk taking (validity)

• It cannot be concluded that reproduction is the reason behind the participants’ behavior

• Ethical considerations of being observed for “mating behavior” without knowing this was the purpose (they did agree to be in the study and were debriefed though)