Landmark Research Studies in Biological Psychology

Key Studies in the Biological Approach to Psychology

Brain Structure, Localization, and Neuroplasticity

Milner (HM) Study: Hippocampus and Memory Consolidation

• Procedure: HM had his hippocampus surgically removed to treat severe epilepsy.
• Findings: After surgery, he could not form new long-term memories (anterograde amnesia) but retained his short-term and procedural memory.
• Conclusion: This demonstrates that the hippocampus is essential for *memory consolidation* and strongly supports the concept of *localization of function* in the brain.

Draganski et al. (2004): Neuroplasticity and Juggling

• Procedure: Participants learned to juggle and were scanned using MRI before practice, after three months of practice, and again after three months of stopping.
• Findings: Grey matter density increased in the mid-temporal areas after practice and subsequently decreased when practice stopped.
• Conclusion: This study provides evidence for *neuroplasticity*, illustrating processes like dendritic branching and pruning in response to environmental demands.

Neurotransmitters, Hormones, and Pheromones

Antonova (2011): Acetylcholine and Spatial Memory

• Procedure: Participants were injected with scopolamine (an acetylcholine antagonist) or a placebo and completed a spatial memory virtual reality (VR) task during fMRI scans.
• Findings: Scopolamine impaired performance and reduced hippocampal activation.
• Conclusion: This shows the crucial role of *acetylcholine* (ACh) in memory function and demonstrates the effect of antagonists on neural processes.

McGaugh & Cahill (1995): Adrenaline, Emotion, and Memory

• Procedure: Participants watched either a neutral or an emotional story. Those in the experimental condition were given propranolol (a beta-blocker that blocks adrenaline).
• Findings: Participants given propranolol remembered the emotional story less well.
• Conclusion: This suggests that *adrenaline* (a hormone) activates the amygdala and enhances memory consolidation, linking emotion directly to memory formation.

Wedekind (1995): Pheromones and Mate Selection (MHC)

• Procedure: Men wore T-shirts for two nights; women were then asked to rate the smell of the shirts.
• Findings: Women generally preferred the scent of men with significantly different Major Histocompatibility Complex (MHC) genes (immune system markers).
• Conclusion: This supports the role of *pheromones* in human behavior and provides evidence for evolutionary mate selection strategies based on biological fitness.

Genetics and Behavior

Caspi et al. (2003): Gene-Environment Interaction and Depression

• Procedure: A cohort of New Zealanders was genotyped for the 5-HTT gene and tracked for life stress and incidence of depression.
• Findings: Those with the short allele of the 5-HTT gene combined with high levels of life stress were significantly more likely to develop depression.
• Conclusion: This study demonstrates *gene-environment interaction* and the genetic influence on psychological disorders.

Kendler et al. (2006): Heritability of Depression (Twin Study)

• Procedure: Over 42,000 twins were interviewed to assess the concordance rate of major depressive disorder.
• Findings: Monozygotic (identical) twins had a higher concordance rate than dizygotic (fraternal) twins, especially in women.
• Conclusion: This supports the *heritability* of depression, utilizing kinship (twin) studies to estimate genetic influence on behavior.

Evolutionary Explanations of Behavior

Buss (1989): Cross-Cultural Mate Preferences

• Procedure: Over 10,000 participants from 37 cultures answered surveys on mate preferences.
• Findings: Women consistently preferred ambition and financial security; men consistently preferred youth and physical appearance.
• Conclusion: This large-scale study supports *evolutionary explanations* for sex differences in mate selection, suggesting preferences maximize reproductive success.