IB Psychology: Unit 1

Evolution

Natural process where traits that help survival and reproduction become more common over generations.

Natural selection

Process by which organisms with advantageous traits are more likely to survive and reproduce.

Adaptation

A trait shaped by natural selection that increases an organism’s chances of surviving in its environment.

Darwin’s finches

Example showing beak shapes adapted to different island food sources (evidence of adaptation).

Comparative approach

Studying animals (like primates) to learn about human evolution and behaviour.

Matsuzawa chimp study

Found chimps have better very-short-term spatial memory than humans; suggests cognitive skills adapt to environment.

Evolutionary psychology

Field that explains mental systems as products of evolution; genes shape mechanisms that produce behaviour.

Disgust (Fessler)

Disgust in early pregnancy may protect the fetus by reducing consumption of risky foods (adaptive response).

Curtis et al. study

Internet study showing people worldwide find disease-related images most disgusting; supports disgust as disease-avoidance.

Limitations of evolutionary explanations

Historical inference is hard to test; risk of “just-so” stories and underestimating culture/learning.

Genes vs behaviour

Genes give tendencies or predispositions; behaviour results from gene–environment interaction, not single genes.

Twin/family/adoption studies

Research methods that estimate genetic influence (concordance rates) but cannot prove direct causation.

Diathesis–stress model

Explains disorders as resulting from genetic vulnerability (diathesis) interacting with environmental stressors.

Ethics in genetic research

Privacy, stigma, and misuse risks; requires informed consent and careful data protection.

Core conclusion

Behaviour reflects evolution, genetics, and environment together — use all three perspectives and apply ethical caution.