Evolutionary Adaptation
Traits or behaviors that improve survival or reproduction become more common over generations. It was established by Charles Darwin.
Natural Selection
The process in which individuals with traits that enhance their genetic fitness are more likely to survive and reproduce. This leads to the gradual increase of beneficial traits in a population over generations.
Massive Modularity Hypothesis
The brain is thought to consist of specialized "modules," each evolved to handle specific survival-related tasks, such as detecting threats or avoiding disease.
Fear as an Evolutionary Response
- Fear is essential for survival, enabling individuals to detect and avoid threats.
- The amygdala, a key brain region, perceives threats and activates the HPA axis, releasing stress hormones like cortisol and adrenaline, preparing the body for fight or flight.
Patient SM and the Amygdala’s Role in Fear
Case studyFeinstein et al. 2011
Aim: To investigate the role of the amygdala in generating fear.
Method: Case study of a patient (SM) with bilateral amygdala damage caused by a genetic condition.
Procedure: Researchers exposed SM to fear-inducing scenarios, such as a pet store with snakes and spiders, a haunted house, and scary films. They also used self-reports and interviews to gather data on her real-life experiences.
Results: SM showed no fear in any scenario. For instance, she eagerly touched dangerous snakes and remained unaffected in the haunted house, even scaring one of the actors herself.
Conclusion: The study highlights the amygdala's critical role in producing a fear response. Without it, SM failed to avoid danger, leading to risky behaviors, such as staying in abusive relationships. This underscores the evolutionary importance of fear for survival and avoiding harm.
Disgust as a Disease-Avoidance Mechanism
- Disgust evolved to protect humans from disease by triggering aversion to harmful substances, such as spoiled food or contaminated objects.
- This response is stronger in women, potentially due to their role in protecting offspring.
Curtis, Aunger, and Rabie (2004)
Aim: To test the hypothesis that disgust is an evolutionary adaptation to avoid disease, where disgust serves as a biological mechanism to reduce the risk of infection.
Method: An online correlational survey with over 77,000 participants from 165 countries.
Procedure:
- Participants rated 20 images on a 1 to 5 disgust scale.
- Images were presented in pairs: one disease-salient (e.g., a plate of organic-looking fluid) and the other non-disease-salient (e.g., blue chemical-looking fluid).
- Participants were also asked who they would not share a toothbrush with, including familiar (e.g., sibling, spouse) and unfamiliar individuals (e.g., postman, boss).
Results:
- Disease-salient images received significantly higher disgust ratings.
- Responses were consistent across cultures and stronger in females.
- Disgust responses declined with age, aligning with reduced reproductive potential.
- Participants were more likely to share a toothbrush with familiar individuals than unfamiliar ones, further supporting disgust as an evolutionary mechanism to avoid disease from unknown sources.
Conclusion: Disgust is a biologically ingrained response to disease-related stimuli, supporting the theory that it evolved as a mechanism to protect against infection and reduce disease risk.
Emotion and Memory Consolidation
- The release of cortisol during emotionally arousing experiences, such as fear, enhances memory consolidation.
- This enables individuals to remember and avoid danger in the future, a critical survival mechanism.
Buchanan and Lovallo (2001)
Aim: To investigate the effect of cortisol on emotional memory consolidation.
Method: Experiment with 48 participants (24 male, 24 female).
Procedure:
- Participants were randomly assigned to a cortisol (20mg) or placebo group.
- They viewed 60 images classified as "arousing pleasant," "arousing unpleasant," or "neutral."
- Memory recall was tested a week later by having participants describe the images to blind scorers.
Results:
- The cortisol group recalled more images overall.
- Emotional (arousing) images were remembered significantly better than neutral ones.
Conclusion: Cortisol enhances memory for emotional events, likely aiding survival by enabling individuals to avoid past dangers or locate resources.
