Animal research ERQ + Lashley

Aim of Martinez and Kesner (1991)

To determine the role of the neurotransmitter acetylcholine in memory formation using rats in a maze-learning task.

Sample in Martinez and Kesner (1991)

Male laboratory rats; the exact number was not reported but was sufficient for three experimental conditions.

Procedure in Martinez and Kesner (1991)

Rats were trained to run a T-maze to find food. They were then divided into three groups: 1) One group received scopolamine, which blocks acetylcholine receptors. 2) The second group received physostigmine, which blocks the enzyme that breaks down acetylcholine, increasing its availability. 3) The third group was a control that received a saline solution. After injections, rats were tested on their ability to complete the maze.

Findings of Martinez and Kesner (1991)

Rats injected with scopolamine took longer to complete the maze and made more errors, while those injected with physostigmine completed it faster and more accurately than controls.

Conclusion of Martinez and Kesner (1991)

Acetylcholine plays a significant role in the formation of spatial memory. The findings support the idea that neurotransmitters influence learning and memory.

Relation of Martinez and Kesner (1991) to Antonova et al.

It provided foundational evidence for acetylcholine's role in memory, leading to human studies like Antonova, which explored similar mechanisms using fMRI and pharmacological blocking in healthy adults.

Aim of Weaver et al. (2004)

To investigate how maternal care influences the expression of stress-related genes in rats through epigenetic modification.

Sample in Weaver et al. (2004)

Laboratory rats separated based on whether their mothers exhibited high or low grooming and nurturing behaviours.

Procedure in Weaver et al. (2004)

Weaver compared rats raised by high-licking and low-licking mothers. They measured stress hormone responses and gene expression in the hippocampus. Cross-fostering was used to see whether the biological or adoptive mother's behaviour influenced the outcome.

Findings of Weaver et al. (2004)

Rats raised by low-nurturing mothers had higher stress responses and showed suppressed expression of the glucocorticoid receptor gene in the hippocampus due to epigenetic methylation. Cross-fostering revealed that maternal behaviour—not genetics—was the main factor.

Conclusion of Weaver et al. (2004)

Maternal care can alter gene expression related to stress response, showing an environmental impact on biological systems via epigenetics.

Relation of Weaver et al. (2004) to Caspi et al. (2003)

Weaver's animal findings about gene-environment interaction parallel Caspi's human study on how the 5-HTT gene moderates the effect of stressful life events on depression, showing that both genetic predispositions and environmental experiences influence behaviour.

Weaver's findings

Weaver's animal findings about gene-environment interaction parallel Caspi's human study on how the 5-HTT gene moderates the effect of stressful life events on depression, showing that both genetic predispositions and environmental experiences influence behaviour.

Aim of Albert et al. (1986)

To examine the relationship between testosterone levels and aggression in male rats.

Sample in Albert et al. (1986)

Male rats that were initially screened to be similar in size and aggression levels.

Procedure in Albert et al. (1986)

Rats were placed in cages and their aggression was measured. Then, they were divided into groups for surgical manipulation: 1) Castration (removing testes, thus eliminating testosterone production), 2) Castration followed by testosterone replacement (tubes with testosterone) 3) Castration with empty tubes, 4) Sham operation. Aggression levels were measured again by recording dominant or aggressive behaviours such as biting or attacking when introduced to another rat.

Findings of Albert et al. (1986)

Castrated rats showed a significant drop in aggression. However, those that received testosterone replacement showed a return to normal levels of aggression, unlike the placebo group.

Conclusion of Albert et al. (1986)

Testosterone levels directly affect aggressive behaviour in rats, supporting the idea that hormones influence social behaviours.

Relation of Albert et al. to Carré et al. (2017)

Albert's study supports the biological basis of testosterone-linked aggression in animals, which complements Carré's human study that suggests testosterone modulates aggression particularly when combined with individual personality traits like dominance.

Strengths of animal research in psychology

- Allows for high experimental control over variables (e.g., hormone levels, neurotransmitters). - Ethical manipulations (e.g., lesioning, pharmacological interventions) that would not be allowed in human studies. - Can establish causal relationships, especially for biological mechanisms. - Enables longitudinal or developmental studies within shorter lifespans.

Limitations of animal research in psychology

- Questionable generalisability to humans due to species differences in brain structure and function.

- Ethical concerns regarding harm, stress, or death of animals.

- Artificial settings may not reflect natural behaviour.

- Complex human behaviours (e.g., emotion, social norms) may not be fully modeled in animals.

Holistic evaluation of animal research in psychology

Animal research has greatly advanced our understanding of the biological underpinnings of behaviour, such as the role of neurotransmitters (Martinez & Kesner), epigenetics (Weaver), and hormones (Albert). These studies have led to ethical and methodologically sound human studies (e.g., Antonova, Caspi, Carré) that replicate or expand upon these findings. However, caution is needed in extrapolating results due to species and cognitive differences. While ethical frameworks exist (e.g., the 3Rs: Replacement, Reduction, Refinement), the moral justification of causing harm to animals for human benefit remains a topic of debate. A triangulated approach—using both human and animal research—yields the most balanced understanding of behaviour.

Karl Lashley (1929)

The study can be used for... (lashley)

1. the role of animal research in understanding human behaviour

2. ethical considerations

3. Localisation of function

Aim - Lashley

The aim of the study is to see if psychological functions are distributed rather than localized

Procedure - Lashley

In this study, he trained a rat to go through a maze without mistakes in search of food, then removed a part of its cortex and observed what effect this would have on its memory of the maze. He removed 10-15% of the cortex on different trials.

Findings - Lashley

- Result of these experiments did not support Lashley's original hypothesis and led him to formulate the following ideas.

- The principle of mass action: the memory of the maze depended on the percentage of cortex destroyed, but not on the location of the lesion.

- Equipotentiality: The idea that one part of the cortex can take over the functions of another part of the cortex when necessary.

Conclusion - Lashley

Based on these observations Lashley concluded that memory is not localized; it is widely distributed across the cortex as a whole. Even if one part of the cortex is lost, other parts may take over the functions of the missing part

Ethical Consideration

Rats in the study were harmed because invasive surgery was performed on their brain. Such studies must ensure that this degree of suffering is absolutely necessary for the purposes of research, that potential benefits of research results justify the experimental procedure, that the minimum number of animals is used, and that approval is obtained from the Ethics Committee.

Evaluation: Strengths (lashley)

- Studying animals helps uncover the way the human brain (memory especially) works, has the potential to help humans, Lashley was one of the first to try and demonstrate localization of function

Evaluation: Weaknesses - Lashley

- Researchers did not control all variables (i.e. rodents still had their sense of smell - could be regarded as a confounding variable

- Extreme holist position

- Rats in the study were harmed because invasive surgery was performed on their brain.

Understanding of the study - Lashley

Experiments with induced brain damage in rats showed that memory is widely distributed rather than localised anywhere in the cortex. Karl Lashley (1929) used carefully controlled induced brain damage in the cortex of rats that were trained to run through a maze