The Biological Level of Analysis
Introduction
At the most basic level of analysis, human beings are biological systems. Our cognitions, emotions and behaviours are products of the anatomy and physiology of our nervous and endocrine systems. Over the last few centuries, discoveries have shown that:
• the nature of the nervous system is electrical in part (Galvani)
• different areas of the brain carry out different functions (Broca)
• small gaps exist between nerve cells that require the action of chemicals to carry neural transmissions across these gaps
• hormones play an important role in our psychological functioning.
A biological perspective is relevant to the study of Psychology in three ways:
1. Comparative method: different species of animal can be studied and compared. This can help in the search to understand human behaviour.
2. Physiology: how the nervous system and hormones work, how the brain functions, how changes in structure and/or function can affect behaviour. For example, we could ask how prescribed drugs to treat depression affect behaviour through their interaction with the nervous system.
3. Investigation of inheritance: what an animal inherits from its parents, mechanisms of inheritance (genetics). For example, we might want to know whether high intelligence is inherited from one generation to the next.
Each of these biological aspects, the comparative, the physiological and the genetic, can help illuminate human behaviour.
Evaluation of the biological level of analysis
In support of the approach
1. We need to know the basis of what makes us behave in certain ways. If we don’t then we cannot really claim to know anything about behaviour at all. Some would claim that all behaviour should be explained on a physiological level because all that we are is contained in our neural and hormonal reactions.
2. If we know the physiological basis of some aspects of behaviour (e.g. depression) then we can treat the problem using drugs, which could solve the problem entirely if it’s simply a straightforward chemical imbalance. Plus, some aspects of physiology and anatomy are very useful when it comes to diagnosing brain damage etc.
3. Evolutionary theory can offer some neat explanations of behaviour that would otherwise be inexplicable (e.g. graffiti, appendix).
4. The more we know about the brain, the more we should be able to explain how we behave: it is the seat of all our knowledge after all.
Criticisms of the approach
1. It’s reductionist, which leads to the following criticisms:
(a) If someone comes to you with depression is it any use to them to tell them that their serotonin receptors are not
functioning properly?
(b) Mind/body problem 1: psychology has great influence on physiology (stress and illness)
(c) Mind/body problem 2: sensation is not necessarily the same as perception
(d) Consciousness: what is it, where is it and is it any use finding it?
(e) What about free will? Biological approach advocates determinism.
2. Evolutionary approach has a number of problems:
(a) Altruism: difficult to explain. Even sociobiologists come up with some very convoluted explanations.
(b) Our developing cortex means that we rely less on instincts and more on “higher” processes.
(c) Our behaviour is very much socially and culturally determined.
3. Genes: Difficult to separate genes and environmental influences on behaviour.
At the most basic level of analysis, human beings are biological systems. Our cognitions, emotions and behaviours are products of the anatomy and physiology of our nervous and endocrine systems. Over the last few centuries, discoveries have shown that:
• the nature of the nervous system is electrical in part (Galvani)
• different areas of the brain carry out different functions (Broca)
• small gaps exist between nerve cells that require the action of chemicals to carry neural transmissions across these gaps
• hormones play an important role in our psychological functioning.
A biological perspective is relevant to the study of Psychology in three ways:
1. Comparative method: different species of animal can be studied and compared. This can help in the search to understand human behaviour.
2. Physiology: how the nervous system and hormones work, how the brain functions, how changes in structure and/or function can affect behaviour. For example, we could ask how prescribed drugs to treat depression affect behaviour through their interaction with the nervous system.
3. Investigation of inheritance: what an animal inherits from its parents, mechanisms of inheritance (genetics). For example, we might want to know whether high intelligence is inherited from one generation to the next.
Each of these biological aspects, the comparative, the physiological and the genetic, can help illuminate human behaviour.
Evaluation of the biological level of analysis
In support of the approach
1. We need to know the basis of what makes us behave in certain ways. If we don’t then we cannot really claim to know anything about behaviour at all. Some would claim that all behaviour should be explained on a physiological level because all that we are is contained in our neural and hormonal reactions.
2. If we know the physiological basis of some aspects of behaviour (e.g. depression) then we can treat the problem using drugs, which could solve the problem entirely if it’s simply a straightforward chemical imbalance. Plus, some aspects of physiology and anatomy are very useful when it comes to diagnosing brain damage etc.
3. Evolutionary theory can offer some neat explanations of behaviour that would otherwise be inexplicable (e.g. graffiti, appendix).
4. The more we know about the brain, the more we should be able to explain how we behave: it is the seat of all our knowledge after all.
Criticisms of the approach
1. It’s reductionist, which leads to the following criticisms:
(a) If someone comes to you with depression is it any use to them to tell them that their serotonin receptors are not
functioning properly?
(b) Mind/body problem 1: psychology has great influence on physiology (stress and illness)
(c) Mind/body problem 2: sensation is not necessarily the same as perception
(d) Consciousness: what is it, where is it and is it any use finding it?
(e) What about free will? Biological approach advocates determinism.
2. Evolutionary approach has a number of problems:
(a) Altruism: difficult to explain. Even sociobiologists come up with some very convoluted explanations.
(b) Our developing cortex means that we rely less on instincts and more on “higher” processes.
(c) Our behaviour is very much socially and culturally determined.
3. Genes: Difficult to separate genes and environmental influences on behaviour.
The Outline
2.1 Outline principles that define the biological level of analysis
1 - There are biological correlates of behaviour
study proving this: Newcomer at al. (1999)
2 - Animal research can provide insight into human behaviour
study proving this: Rosenzweig and Bennet (1972)
3 - Human behaviour is, to some extent, genetically based
study proving this: Bouchard et al. (1990)
2.2 Examine one study related to localisation of function in the brain
studies proving this: HM Study or Phineas Gage
2.3 Explain, using one or more examples, the effects of neurotransmission on human behaviour
study proving this: Martinez and Kesner (1991)
2.4 Explain, using one or more examples, the function of two hormones on human behaviour
studies proving this: Baumgartner et al. (2008) and Newcomer et al. (1999)
watch my voice thread on testosterone and oestrogen: http://voicethread.com/?#u3264092.b3723441.i19328439
2.5 Discuss two effects of the environment on physiological processes
Effect 1 - Environmental effects on dentritic branching (brain plasticity)
study proving this: Rosenzweig and Bennet (1972)
Effect 2 - Mirror Neurons
study proving this:
2.6 Examine one interaction between cognition and physiology in terms of behaviour
study proving this: Davidson et al. (2004)
2.7 Discuss the use of brain imaging technologies in investigating the relationship between biological factors and behaviour
study proving this: Harris and Fiske (2006)
2.8 Discuss the extent to which genetics influences behaviour
study proving this: Bouchard et al. (1990)
2.9 Examine one evolutionary explanation of behaviour
study proving this: Fessler et al. (2005)
2.10 Discuss ethical considerations in research into genetic influences on behaviour
no study proving this ^
1 - There are biological correlates of behaviour
study proving this: Newcomer at al. (1999)
2 - Animal research can provide insight into human behaviour
study proving this: Rosenzweig and Bennet (1972)
3 - Human behaviour is, to some extent, genetically based
study proving this: Bouchard et al. (1990)
2.2 Examine one study related to localisation of function in the brain
studies proving this: HM Study or Phineas Gage
2.3 Explain, using one or more examples, the effects of neurotransmission on human behaviour
study proving this: Martinez and Kesner (1991)
2.4 Explain, using one or more examples, the function of two hormones on human behaviour
studies proving this: Baumgartner et al. (2008) and Newcomer et al. (1999)
watch my voice thread on testosterone and oestrogen: http://voicethread.com/?#u3264092.b3723441.i19328439
2.5 Discuss two effects of the environment on physiological processes
Effect 1 - Environmental effects on dentritic branching (brain plasticity)
study proving this: Rosenzweig and Bennet (1972)
Effect 2 - Mirror Neurons
study proving this:
2.6 Examine one interaction between cognition and physiology in terms of behaviour
study proving this: Davidson et al. (2004)
2.7 Discuss the use of brain imaging technologies in investigating the relationship between biological factors and behaviour
study proving this: Harris and Fiske (2006)
2.8 Discuss the extent to which genetics influences behaviour
study proving this: Bouchard et al. (1990)
2.9 Examine one evolutionary explanation of behaviour
study proving this: Fessler et al. (2005)
2.10 Discuss ethical considerations in research into genetic influences on behaviour
no study proving this ^
The Studies Relevant to the BLOA
Newcomer at al. (1999)
Aim: To investigate how levels of cortisol interfere with verbal declarative memory.
Procedure: A self-selected sample (recruited through advertisement) of 51 normal and healthy people aged 18–30 was used. It was a randomized, controlled, double-blind experiment running for four days. All participants gave informed consent. There were three experimental conditions: 1. A high level of cortisol (tablet of 160 mg per day), equivalent to cortisol levels in the blood as a consequence of a major stressful event. 2. A low level of cortisol (tablet of 40 mg per day), equivalent to cortisol levels in the blood as a consequence of a minor stressful event. 3. A placebo (tablet of no active ingredient).
Results: The high-level group performed worse on the verbal declarative memory test than the low-level group. They performed below placebo levels after day 1. The low-level group (mild stress) showed no memory decrease.
Conclusion: The experiment shows that an increase in cortisol over a period has a negative effect on memory.
Strengths vs. Weaknesses: This was a controlled randomized experiment so it was possible to establish a cause-effect relationship between levels of cortisol and scores on a verbal declarative memory test.
Ethical Considerations: Ethical issues were observed with informed consent. The negative effect of taking high dosages of cortisol was reversible so no harm was done.
Rosenzweig & Bennet (1972)
Aim: To investigate the effect of enrichment or deprivation on the development of neurons in the cerebral cortex in rats
Background Information: Rosenzweig & Bennet wanted to see if changing the level of stimuli in the environment would result in physical changes in the brain. Neuroplasticity refers to the ability of the brain to change as a result of one's experience. Before this research was done, scientists believed that the brain changed up until a critical period in childhood. After that, no changes in the brain were believed possible.
Research method: Experiment
Procedure: Rats were placed in either a stimulating environment (toys) or a deprived environment (no toys). Rats were placed in either an enriched environment (EC) or an impoverished condition (IC). The rats spent 30 or 60 days in their environment and then they were dissected.
Results: Post mortem studies of the rats´ brains showed that those that had been in a stimulating environment had an increased thickness in the cortex.
Strengths vs. Limitations: The research challenged the belief that brain weight cannot change. This was an important finding. The experiment was a rigorously controlled laboratory experiment so it was possible to establish a cause-effect relationship. The experiment used animal models, so it may be difficult to generalize to humans unless research with humans provides the same results. The research results have been replicated many times, so it is now a well-established fact that an enriched environment provides a much better background for brain development than a poor environment.
Ethical Considerations: There are ethical issues in the use of animals in research like this. The rats used were perhaps suffering from boredom but they were not harmed. The rats were killed after the test period in order to study changes in the brain. Since the results contributed to a much better understanding of the role of environmental factors in brain plasticity it could be argued that the research was justified in spite of the ethical issues.
Minnesota Twin Study (Bouchard 1990)
Aim: To discover to what extent environmental factors affect humans as opposed to genetic influence
Procedure: Monozygotic (identical) twins that were raised apart were compared to monozygotic twins raised together over a long period of time (making this a longitudinal study)
Results: Bouchard found that both twins reared together or apart had a relatively equal chance of having similar personalities, interests and attitudes.
Conclusion: Bouchard et al. determined a heritability estimate of 70% - 70% of intelligence can be attributed to genetic inheritance. 30% attributed to other factors.
Strengths vs. Limitations: The strengths of this study is that the size of it means it can be generalised easily, the nature of the sample was cross cultural meaning that it was fair and the mean age of participants is 41 years old as opposed to previous studies that used adolescents. The limitations are that the study relied on media coverage to recruit participants, the frequency of contact between the twins prior to the study wasn't controlled and also that twins reared together may not have experienced the same environment.
Ethical Considerations: There are ethical concerns with the way twins were reunited as it was not done in a planned process and there could have been some emotional issues with this. The researchers should have been more careful.
Phineas Gage (1984)
Procedure: Much of what psychologists know about the human brain has come from case studies of individuals who had brain surgery or brain damage in accidents. Phineas Gage is one such case study. He was a young railroad worker in 1848 who had an accident at work. He was forcing gun powder into a rock with a long iron rod when the gun powder exploded. The iron rod shot through his cheek and out the top of his head, resulting in substantial damage to his frontal lobe. Incredibly, he did not appear to be very hurt. His memory and mental abilities were intact, and he could speak and work. However, his personality totally changed. Before the accident, he had been nice to be around, but afterward he became ill-tempered and dishonest. He lost his job and ended up working as an exhibit at fairs.
Results: In his 1848 report, as Gage was just completing his physical recovery, Harlow had only hinted at possible psychological symptoms: "The mental manifestations of the patient, I leave to a future communication. I think the case ... is exceedingly interesting to the enlightened physiologist and intellectual philosopher." And after observing Gage for several weeks in late 1849, Henry Jacob Bigelow, Professor of Surgery at Harvard, went so far as to say that Gage was "quite recovered in faculties of body and mind," there being "inconsiderable disturbance of function".
It was not until 1868 that Harlow gave particulars of the mental changes found today (though usually in exaggerated or distorted form) in most presentations of the case. In memorable language, he described the pre-accident Gage as having been hard-working, responsible, and "a great favourite" with the men in his charge, his employers having regarded him as "the most efficient and capable foreman in their employ". But these same employers, some months after Gage's accident, "considered the change in his mind so marked that they could not give him his place again":
Conclusion: Neurologist Antonio Damasio uses Gage to illustrate a hypothesized link between the frontal lobes, emotion and practical decision-making. But any theory that looks to Gage for support faces the difficulty that the nature, extent, and duration of the injury's effects on his mental state are very uncertain.
Strengths and limitations: The strength of this study are that it has helped psychologists learn so much more about the brain and learning about the different sections of the brain. Some limitations of this case study are that we can’t know for certain that his behaviour was different before, since it was not really investigate. Also we can’t be a hundred present sure how much of the changes in behaviour was due to the physical impact of the injury on the brain and how much to how he handled his accident and the resulting injury. However, several other experiments were conducted that support the found results in this case study.
Ethical Considerations: He wasn’t actually injured during the study because that had happened before, nevertheless one could argue that his identity should have been kept secret because the study doesn’t portray him in a positive light.
Martinez and Kesner (1991)
Aim: The purpose of this experiment is determining the role of the neurotransmitter acetylcholine on memory.
Procedure: Rats were trained to go through a maze and get to the end, where they received food. Once the rats were able to do this, Researchers injected one group of rats with scopolamine, which blocks acetylcholine receptor sites thus decreasing available acetylcholine. Then, they injected a second group of rats with physostigmine, which blocks the production of cholinesterase. The third group, the control group, were not given any injections.
Conclusion: The more acetylcholine rats go through the maze faster. Therefore it should be said that acetylcholine affects the memory of the brain.
Strengths vs. Limitations: The strengths of this research lie in its design and its application. The use of an experimental method with a control group made it possible to establish a cause and-effect relationship between levels of acetylcholine and memory. The limitation of the research is that it is questionable to what extent these findings can be generalized to humans. Is it possible to apply research on rats to human beings? Was the use of animals justified?
Ethical Considerations: There is controversy on whether the animals were looked after during or after the experiment.
Baumgartner et al. (2008)
Aim: The aim of the study was to investigate the role of oxytocin following breaches of trust.
Procedure: This was an experimental study where the researchers used neuroimaging. First, 49 participants were placed in a fMRI scanner. They received either oxytocin or placebo via a nasal spray. Participants were then told to act as investors in several rounds of a trust game with different trustees. They were also told that they were to engage in a risk game, which is the same as a trust game in terms of financial risk but it is played against a computer instead of a human partner.
The participants received feedback from the experimenters. The procedure was divided into a pre-feedback phase and a post-feedback phase and the feedback was given in between the two. The feedback given indicated that about 50% of their decisions (in both kinds of games) resulted in poor investment because their trust was broken.
Results: After playing several games with different people the participants were informed that their trust was broken 50% of the time. This caused the participants who received placebo to invest less, however, the ones that received oxytocin continued to invest at the same rate.
Conclusion: These results suggest that oxytocin increases humans’ trust when it comes to making economic decisions.
Strengths vs. Limitations: The experiment is quite limited, though, because it only investigated the effect on oxytocin while making economic decisions, it would be unreliable to generalize the findings and to say that higher levels of oxytocin make people trust more. In order to make this generalization many more different experiments would have to be conducted and the other functions of oxytocin would have to be investigated. Furthermore, another limitation of the experiment is that one has to wonder if some of the participants were generally more trustworthy than others regardless to whether they received oxytocin or not.
Ethical Considerations: As far as people know, no ethical guidelines were breeched
Bremner et al. (2003)
Aim: to measure the volume of the hippocampus based on the theory that prolonged stress may reduce the volume of the hippocampus due to increased cortisol levels.
Procedure: MRI scans were made of the brains of the participants and participants completed memory tests (remembering a story or a list of words).
Results: The researchers found that there were deficits in short-term memory and then performed MRI scans of the participants brains. They found that the hippocampus was smaller is PTSD patients than in a a control group. The veterans with most memory problems also had the smallest hippocampus.
Conclusion: The findings show a clear correlation between a number of years of abuse and measured by a trauma test, memory problems and hippocampal volume. People suffering from PTSD often suffer from other psychological disorders (e.g. depression) which could perhaps also play a role in the observed changes in the brain.
Strengths vs. Limitations: This study was well controlled yet the sample was very small; making it difficult to say anything definite about the relationship between the trauma and the hippocampal volume. Also there could be alternative explanations to differences in hippocampal volume (e.g. that people who suffer from PTSD often suffer from depression as well). Depression is also associated with reduction of the hippocampus. However, the findings of a large reduction of hippocampal volume in combat-related PTSD has been replicated many times.
Ethical Considerations: There are no obvious ethical considerations, yet there should have been a test to make sure that the scans were safe to be used upon human brains. Apart from this, all areas were without ethical conflict.
Richard Davidson (2004)
Aim: The aim of Davidson’s study was to observe the difference between the brain activity of those who spend a lot of time meditating and those who have never before.
Procedure: Using a PET scan, Davidson observed that two of the controls and all of the monks experienced an increase in the number of gamma waves in their brain during meditation. Gamma waves have been linked to higher reasoning faculties.
Conclusion: The synchronized gamma-wave area of the monks’ brains during meditation on love and compassion was found to be larger than the corresponding activation of the volunteers’ brains. This led Davidson to argue that meditation could have significant long-term effects on the brain and the way it processes emotions.
Strengths vs. Limitations: The strengths show are the results as they show us how influential meditating can be and how calming this sensation can be. It was also a simple concept that made it then easier to conduct a study from it. The experiment wasn’t repeated and cannot really prove that monks feel more compassion that those that don’t show the same brain waves through the scan.
Ethical Considerations: We aren't sure if the results in this study were 100% accurate and I think there should have been a retake of the experiment - just to prove their ideas.
Harris and Fiske (2006)
Aim: to find the biological correlates of stereotypes and prejudice
Procedure: The researchers scanned students while they were watching either pictures of different humans or objects. It was predicted that the medial prefrontal cortex would be active when participants looked at humans but not when they looked at objects.
Results: This was found except when participants looked at pictures of people from extreme out groups such as the homeless and addicts. Brain regions related to ‘disgust’ were activated and there was no activity in the prefrontal cortex.
Conclusion: The researchers concluded that this indicated a dehumanization of the out groups. These groups were apparently viewed as ‘disgusting objects’ and not people.
Strengths vs. Limitations: The strengths of fMRI include; it does not use radioactive substances and it can record activity in all regions of the brain. However the focus is mostly on localized functioning in the brain and does not take into account the distributed nature of processing in neural networks. Also, the results are correlational so it is not possible to establish cause-effect relationships. Another limitation deals with localization of function. It may be possible to identify brain structures that are active during a task but, since most structures are linked to other structures in networks, it is not possible at this point to say definitely where things happen in the brain.
Ethical Considerations: There were no apparent considerations breeched.
Fessler et al. (2005)
Aim: To investigate if disgust sensitivity in the first trimester of pregnancy was elevated as predicted.
Procedure: A Web-based survey was completed by 691 women recruited through pregnancy-related Web sites. No compensation was offered for participation. The women’s mean age was 28.1 years. On the Web-based questionnaire, the participants (1) indicated their current level of nausea using a 16-point scale and (2) answered questions to test their disgust sensitivity in eight different areas (e.g. food; contact with animals, body products, and dead animals; hygiene; contact with toilets)
Results: Overall, disgust sensitivity related to food and body products in women in the first trimester was higher compared to those in the second and third trimesters. Disgust was particularly elevated in relation to food, which was exactly what the researchers had predicted
Conclusion: Food-borne diseases are particularly dangerous to women in the first trimester and therefore it was predicted that disgust sensitivity related to food would be high. This was supported by the results. The results may indicate that nausea and vomiting are evolved behaviour because they limit the likelihood that pregnant women will eat dangerous food.
Strengths vs. Limitations: The data was collected through questionnaires. Self-reports may not be reliable. This is not an effective way of measuring disgust. It would have been more reliable to confront participants with real disgust-eliciting objects. The effect sizes were not big but significant. The findings are supported by other studies (e.g. Curtiss et al. 2004) showing that images that threaten the immune system are judged as more disgusting.
Ethical Considerations: It is difficult to test evolutionary theories and not much is known about the life of early humans. Also, evolutionary explanations tend to focus on biological factors and underestimate cultural influences.
Other Useful Studies
The Sperry Study (1968)
Aim: The aim of the experiment was to understand how the two hemispheres of the brain function and when they have been disconnected.
Research Method: A natural experiment as he studied participants who had undergone the operation to treat epilepsy. They came to him ‘naturally’ as participants with a unique brain structure as the results of the surgery.
Procedure: Sperry used specially designed apparatus which allowed stimuli to be presented to one hemisphere at a time. Participants had one eye covered and centred their gaze on a point on a screen in front of them. Visual information was displayed to one half of the visual field for a tenth of a second. Below the screen was a space which shielded participants hand from view so that the information from an object placed in one hand would only be received by the corresponding brain hemisphere.
Results: His findings suggested that each hemisphere was operating independently. When a piece of information was presented to the left visual field (the right hemisphere) it would only be recognized again if seen by the same visual field.
Conclusion: Sperry argued that his studies give considerable support to his argument of lateralisation of function. That is, those different areas of the brain specialise on different tasks, such as the left hand side being responsible for language. He also went on to argue that each hemisphere has its own perceptions and memories and experiences.
Strengths vs. Limitations: A strength of Sperry’s procedure was that by using a mixture of quasi-experiments and clinical case studies, he was able to combine qualitative and quantitative approaches. The quasi-experiment is a quantitative method of data collection, that is, it provides information in the form of numbers and frequencies, and so can be easily analysed statistically. The information that is gathered is regarded as fairly reliable but not very valid. On the other hand, the case study is a qualitative method of data collection which is concerned with describing meaning. It is argued that what the case study loses on reliability it gains in terms of validity. Therefore a combination of these methods allows for the collection of statistically reliable information to be enhanced by information about the research participants’ explanations.
A major criticism of the procedure was Sperry’s sample. 11 participants is a very small sample, however Sperry may not have had any control over this - there may not be very many split-brain patients available to study. The small sample also enabled Sperry to gain more in-depth data. The 11 split-brain patients were lumped together as the experimental group, but some of the patients had experienced more de-connection than others. We also cannot be sure how long each of the participants had experienced ineffective drug therapy which could have been affecting the findings.
A further weakness of the study relates to ecological validity. The findings of the study would be unlikely to be found in a real life situation because a person with severed corpus callosum who had both eyes would be able to compensate for such a loss.
Ethical Considerations: as far as people know, there were no ethical considerations breeched in this study
Aim: To investigate how levels of cortisol interfere with verbal declarative memory.
Procedure: A self-selected sample (recruited through advertisement) of 51 normal and healthy people aged 18–30 was used. It was a randomized, controlled, double-blind experiment running for four days. All participants gave informed consent. There were three experimental conditions: 1. A high level of cortisol (tablet of 160 mg per day), equivalent to cortisol levels in the blood as a consequence of a major stressful event. 2. A low level of cortisol (tablet of 40 mg per day), equivalent to cortisol levels in the blood as a consequence of a minor stressful event. 3. A placebo (tablet of no active ingredient).
Results: The high-level group performed worse on the verbal declarative memory test than the low-level group. They performed below placebo levels after day 1. The low-level group (mild stress) showed no memory decrease.
Conclusion: The experiment shows that an increase in cortisol over a period has a negative effect on memory.
Strengths vs. Weaknesses: This was a controlled randomized experiment so it was possible to establish a cause-effect relationship between levels of cortisol and scores on a verbal declarative memory test.
Ethical Considerations: Ethical issues were observed with informed consent. The negative effect of taking high dosages of cortisol was reversible so no harm was done.
Rosenzweig & Bennet (1972)
Aim: To investigate the effect of enrichment or deprivation on the development of neurons in the cerebral cortex in rats
Background Information: Rosenzweig & Bennet wanted to see if changing the level of stimuli in the environment would result in physical changes in the brain. Neuroplasticity refers to the ability of the brain to change as a result of one's experience. Before this research was done, scientists believed that the brain changed up until a critical period in childhood. After that, no changes in the brain were believed possible.
Research method: Experiment
Procedure: Rats were placed in either a stimulating environment (toys) or a deprived environment (no toys). Rats were placed in either an enriched environment (EC) or an impoverished condition (IC). The rats spent 30 or 60 days in their environment and then they were dissected.
Results: Post mortem studies of the rats´ brains showed that those that had been in a stimulating environment had an increased thickness in the cortex.
Strengths vs. Limitations: The research challenged the belief that brain weight cannot change. This was an important finding. The experiment was a rigorously controlled laboratory experiment so it was possible to establish a cause-effect relationship. The experiment used animal models, so it may be difficult to generalize to humans unless research with humans provides the same results. The research results have been replicated many times, so it is now a well-established fact that an enriched environment provides a much better background for brain development than a poor environment.
Ethical Considerations: There are ethical issues in the use of animals in research like this. The rats used were perhaps suffering from boredom but they were not harmed. The rats were killed after the test period in order to study changes in the brain. Since the results contributed to a much better understanding of the role of environmental factors in brain plasticity it could be argued that the research was justified in spite of the ethical issues.
Minnesota Twin Study (Bouchard 1990)
Aim: To discover to what extent environmental factors affect humans as opposed to genetic influence
Procedure: Monozygotic (identical) twins that were raised apart were compared to monozygotic twins raised together over a long period of time (making this a longitudinal study)
Results: Bouchard found that both twins reared together or apart had a relatively equal chance of having similar personalities, interests and attitudes.
Conclusion: Bouchard et al. determined a heritability estimate of 70% - 70% of intelligence can be attributed to genetic inheritance. 30% attributed to other factors.
Strengths vs. Limitations: The strengths of this study is that the size of it means it can be generalised easily, the nature of the sample was cross cultural meaning that it was fair and the mean age of participants is 41 years old as opposed to previous studies that used adolescents. The limitations are that the study relied on media coverage to recruit participants, the frequency of contact between the twins prior to the study wasn't controlled and also that twins reared together may not have experienced the same environment.
Ethical Considerations: There are ethical concerns with the way twins were reunited as it was not done in a planned process and there could have been some emotional issues with this. The researchers should have been more careful.
Phineas Gage (1984)
Procedure: Much of what psychologists know about the human brain has come from case studies of individuals who had brain surgery or brain damage in accidents. Phineas Gage is one such case study. He was a young railroad worker in 1848 who had an accident at work. He was forcing gun powder into a rock with a long iron rod when the gun powder exploded. The iron rod shot through his cheek and out the top of his head, resulting in substantial damage to his frontal lobe. Incredibly, he did not appear to be very hurt. His memory and mental abilities were intact, and he could speak and work. However, his personality totally changed. Before the accident, he had been nice to be around, but afterward he became ill-tempered and dishonest. He lost his job and ended up working as an exhibit at fairs.
Results: In his 1848 report, as Gage was just completing his physical recovery, Harlow had only hinted at possible psychological symptoms: "The mental manifestations of the patient, I leave to a future communication. I think the case ... is exceedingly interesting to the enlightened physiologist and intellectual philosopher." And after observing Gage for several weeks in late 1849, Henry Jacob Bigelow, Professor of Surgery at Harvard, went so far as to say that Gage was "quite recovered in faculties of body and mind," there being "inconsiderable disturbance of function".
It was not until 1868 that Harlow gave particulars of the mental changes found today (though usually in exaggerated or distorted form) in most presentations of the case. In memorable language, he described the pre-accident Gage as having been hard-working, responsible, and "a great favourite" with the men in his charge, his employers having regarded him as "the most efficient and capable foreman in their employ". But these same employers, some months after Gage's accident, "considered the change in his mind so marked that they could not give him his place again":
Conclusion: Neurologist Antonio Damasio uses Gage to illustrate a hypothesized link between the frontal lobes, emotion and practical decision-making. But any theory that looks to Gage for support faces the difficulty that the nature, extent, and duration of the injury's effects on his mental state are very uncertain.
Strengths and limitations: The strength of this study are that it has helped psychologists learn so much more about the brain and learning about the different sections of the brain. Some limitations of this case study are that we can’t know for certain that his behaviour was different before, since it was not really investigate. Also we can’t be a hundred present sure how much of the changes in behaviour was due to the physical impact of the injury on the brain and how much to how he handled his accident and the resulting injury. However, several other experiments were conducted that support the found results in this case study.
Ethical Considerations: He wasn’t actually injured during the study because that had happened before, nevertheless one could argue that his identity should have been kept secret because the study doesn’t portray him in a positive light.
Martinez and Kesner (1991)
Aim: The purpose of this experiment is determining the role of the neurotransmitter acetylcholine on memory.
Procedure: Rats were trained to go through a maze and get to the end, where they received food. Once the rats were able to do this, Researchers injected one group of rats with scopolamine, which blocks acetylcholine receptor sites thus decreasing available acetylcholine. Then, they injected a second group of rats with physostigmine, which blocks the production of cholinesterase. The third group, the control group, were not given any injections.
Conclusion: The more acetylcholine rats go through the maze faster. Therefore it should be said that acetylcholine affects the memory of the brain.
Strengths vs. Limitations: The strengths of this research lie in its design and its application. The use of an experimental method with a control group made it possible to establish a cause and-effect relationship between levels of acetylcholine and memory. The limitation of the research is that it is questionable to what extent these findings can be generalized to humans. Is it possible to apply research on rats to human beings? Was the use of animals justified?
Ethical Considerations: There is controversy on whether the animals were looked after during or after the experiment.
Baumgartner et al. (2008)
Aim: The aim of the study was to investigate the role of oxytocin following breaches of trust.
Procedure: This was an experimental study where the researchers used neuroimaging. First, 49 participants were placed in a fMRI scanner. They received either oxytocin or placebo via a nasal spray. Participants were then told to act as investors in several rounds of a trust game with different trustees. They were also told that they were to engage in a risk game, which is the same as a trust game in terms of financial risk but it is played against a computer instead of a human partner.
The participants received feedback from the experimenters. The procedure was divided into a pre-feedback phase and a post-feedback phase and the feedback was given in between the two. The feedback given indicated that about 50% of their decisions (in both kinds of games) resulted in poor investment because their trust was broken.
Results: After playing several games with different people the participants were informed that their trust was broken 50% of the time. This caused the participants who received placebo to invest less, however, the ones that received oxytocin continued to invest at the same rate.
Conclusion: These results suggest that oxytocin increases humans’ trust when it comes to making economic decisions.
Strengths vs. Limitations: The experiment is quite limited, though, because it only investigated the effect on oxytocin while making economic decisions, it would be unreliable to generalize the findings and to say that higher levels of oxytocin make people trust more. In order to make this generalization many more different experiments would have to be conducted and the other functions of oxytocin would have to be investigated. Furthermore, another limitation of the experiment is that one has to wonder if some of the participants were generally more trustworthy than others regardless to whether they received oxytocin or not.
Ethical Considerations: As far as people know, no ethical guidelines were breeched
Bremner et al. (2003)
Aim: to measure the volume of the hippocampus based on the theory that prolonged stress may reduce the volume of the hippocampus due to increased cortisol levels.
Procedure: MRI scans were made of the brains of the participants and participants completed memory tests (remembering a story or a list of words).
Results: The researchers found that there were deficits in short-term memory and then performed MRI scans of the participants brains. They found that the hippocampus was smaller is PTSD patients than in a a control group. The veterans with most memory problems also had the smallest hippocampus.
Conclusion: The findings show a clear correlation between a number of years of abuse and measured by a trauma test, memory problems and hippocampal volume. People suffering from PTSD often suffer from other psychological disorders (e.g. depression) which could perhaps also play a role in the observed changes in the brain.
Strengths vs. Limitations: This study was well controlled yet the sample was very small; making it difficult to say anything definite about the relationship between the trauma and the hippocampal volume. Also there could be alternative explanations to differences in hippocampal volume (e.g. that people who suffer from PTSD often suffer from depression as well). Depression is also associated with reduction of the hippocampus. However, the findings of a large reduction of hippocampal volume in combat-related PTSD has been replicated many times.
Ethical Considerations: There are no obvious ethical considerations, yet there should have been a test to make sure that the scans were safe to be used upon human brains. Apart from this, all areas were without ethical conflict.
Richard Davidson (2004)
Aim: The aim of Davidson’s study was to observe the difference between the brain activity of those who spend a lot of time meditating and those who have never before.
Procedure: Using a PET scan, Davidson observed that two of the controls and all of the monks experienced an increase in the number of gamma waves in their brain during meditation. Gamma waves have been linked to higher reasoning faculties.
Conclusion: The synchronized gamma-wave area of the monks’ brains during meditation on love and compassion was found to be larger than the corresponding activation of the volunteers’ brains. This led Davidson to argue that meditation could have significant long-term effects on the brain and the way it processes emotions.
Strengths vs. Limitations: The strengths show are the results as they show us how influential meditating can be and how calming this sensation can be. It was also a simple concept that made it then easier to conduct a study from it. The experiment wasn’t repeated and cannot really prove that monks feel more compassion that those that don’t show the same brain waves through the scan.
Ethical Considerations: We aren't sure if the results in this study were 100% accurate and I think there should have been a retake of the experiment - just to prove their ideas.
Harris and Fiske (2006)
Aim: to find the biological correlates of stereotypes and prejudice
Procedure: The researchers scanned students while they were watching either pictures of different humans or objects. It was predicted that the medial prefrontal cortex would be active when participants looked at humans but not when they looked at objects.
Results: This was found except when participants looked at pictures of people from extreme out groups such as the homeless and addicts. Brain regions related to ‘disgust’ were activated and there was no activity in the prefrontal cortex.
Conclusion: The researchers concluded that this indicated a dehumanization of the out groups. These groups were apparently viewed as ‘disgusting objects’ and not people.
Strengths vs. Limitations: The strengths of fMRI include; it does not use radioactive substances and it can record activity in all regions of the brain. However the focus is mostly on localized functioning in the brain and does not take into account the distributed nature of processing in neural networks. Also, the results are correlational so it is not possible to establish cause-effect relationships. Another limitation deals with localization of function. It may be possible to identify brain structures that are active during a task but, since most structures are linked to other structures in networks, it is not possible at this point to say definitely where things happen in the brain.
Ethical Considerations: There were no apparent considerations breeched.
Fessler et al. (2005)
Aim: To investigate if disgust sensitivity in the first trimester of pregnancy was elevated as predicted.
Procedure: A Web-based survey was completed by 691 women recruited through pregnancy-related Web sites. No compensation was offered for participation. The women’s mean age was 28.1 years. On the Web-based questionnaire, the participants (1) indicated their current level of nausea using a 16-point scale and (2) answered questions to test their disgust sensitivity in eight different areas (e.g. food; contact with animals, body products, and dead animals; hygiene; contact with toilets)
Results: Overall, disgust sensitivity related to food and body products in women in the first trimester was higher compared to those in the second and third trimesters. Disgust was particularly elevated in relation to food, which was exactly what the researchers had predicted
Conclusion: Food-borne diseases are particularly dangerous to women in the first trimester and therefore it was predicted that disgust sensitivity related to food would be high. This was supported by the results. The results may indicate that nausea and vomiting are evolved behaviour because they limit the likelihood that pregnant women will eat dangerous food.
Strengths vs. Limitations: The data was collected through questionnaires. Self-reports may not be reliable. This is not an effective way of measuring disgust. It would have been more reliable to confront participants with real disgust-eliciting objects. The effect sizes were not big but significant. The findings are supported by other studies (e.g. Curtiss et al. 2004) showing that images that threaten the immune system are judged as more disgusting.
Ethical Considerations: It is difficult to test evolutionary theories and not much is known about the life of early humans. Also, evolutionary explanations tend to focus on biological factors and underestimate cultural influences.
Other Useful Studies
The Sperry Study (1968)
Aim: The aim of the experiment was to understand how the two hemispheres of the brain function and when they have been disconnected.
Research Method: A natural experiment as he studied participants who had undergone the operation to treat epilepsy. They came to him ‘naturally’ as participants with a unique brain structure as the results of the surgery.
Procedure: Sperry used specially designed apparatus which allowed stimuli to be presented to one hemisphere at a time. Participants had one eye covered and centred their gaze on a point on a screen in front of them. Visual information was displayed to one half of the visual field for a tenth of a second. Below the screen was a space which shielded participants hand from view so that the information from an object placed in one hand would only be received by the corresponding brain hemisphere.
Results: His findings suggested that each hemisphere was operating independently. When a piece of information was presented to the left visual field (the right hemisphere) it would only be recognized again if seen by the same visual field.
Conclusion: Sperry argued that his studies give considerable support to his argument of lateralisation of function. That is, those different areas of the brain specialise on different tasks, such as the left hand side being responsible for language. He also went on to argue that each hemisphere has its own perceptions and memories and experiences.
Strengths vs. Limitations: A strength of Sperry’s procedure was that by using a mixture of quasi-experiments and clinical case studies, he was able to combine qualitative and quantitative approaches. The quasi-experiment is a quantitative method of data collection, that is, it provides information in the form of numbers and frequencies, and so can be easily analysed statistically. The information that is gathered is regarded as fairly reliable but not very valid. On the other hand, the case study is a qualitative method of data collection which is concerned with describing meaning. It is argued that what the case study loses on reliability it gains in terms of validity. Therefore a combination of these methods allows for the collection of statistically reliable information to be enhanced by information about the research participants’ explanations.
A major criticism of the procedure was Sperry’s sample. 11 participants is a very small sample, however Sperry may not have had any control over this - there may not be very many split-brain patients available to study. The small sample also enabled Sperry to gain more in-depth data. The 11 split-brain patients were lumped together as the experimental group, but some of the patients had experienced more de-connection than others. We also cannot be sure how long each of the participants had experienced ineffective drug therapy which could have been affecting the findings.
A further weakness of the study relates to ecological validity. The findings of the study would be unlikely to be found in a real life situation because a person with severed corpus callosum who had both eyes would be able to compensate for such a loss.
Ethical Considerations: as far as people know, there were no ethical considerations breeched in this study