Animal research / animal models
Comprehensive study guide for IB Psychology
Study Notes
Mark Scheme
SECTION A MARK SCHEME (4 marks) Must Include: • Biological continuity across species • Homologous structures (similar biology, shared ancestry) • 3Rs: Replacement (alternatives), Reduction (minimize animals), Refinement (minimize suffering) • Named animal model (e.g. rats) • Animal finding linked to human equivalent • Homology assumption explicitly stated
Link Formula: "Animal models like [species] share [homologous structure/system] with humans, enabling ethical research that extends to [human behaviour]."
Watch Out: Don't ignore ethical issues—always mention the 3Rs. Don't assume homology without stating it explicitly.
SECTION B MARK SCHEME (6 marks) 0 marks: No relevant knowledge. 1–2 marks: Basic definition; minimal application. 3–4 marks: Homology and/or 3Rs mentioned; partial application. 5–6 marks: "Biological continuity" and "homologous" are the exact required terms; 3Rs demonstrates ethical awareness; dopamine reward pathway in rats explicitly linked to human addiction via the homology assumption; "inaccessible in human subjects" correctly justifies the use of animal models.
Why Full Marks
"Biological continuity" and "homologous" are the exact required terms; 3Rs demonstrates ethical awareness; dopamine reward pathway in rats explicitly linked to human addiction via the homology assumption; "inaccessible in human subjects" correctly justifies the use of animal models.
Model Answer
Section A Sample Answer
Animal models involve using non-human animals to investigate biological mechanisms that would be unethical or impractical to study in humans. This is based on the principle of biological continuity, suggesting that the brain structures and neurochemistry of certain animals are homologous (similar in origin and function) to those in humans. Such research typically adheres to the "3Rs" (Replacement, Reduction, and Refinement).
An example is the use of rats to study the biology of addiction. Researchers utilize rats to map the dopamine "reward pathway" in response to substance use. Because the dopamine system in rats is homologous to that in humans, these findings help explain the biological reinforcement of addiction. This demonstrates how animal models allow researchers to investigate biological mechanisms of addiction that are inaccessible in human subjects, while the homology assumption supports the generalization of these findings to human behavior.
Section B Sample Answer
Animal models involve using non-human animals to study biological processes that may be generalized to humans based on evolutionary continuity. Researchers could use an "Enriched Environment" model—mimicking the hub's digital tools and social interaction with varied stimuli and social housing—versus a "Standard" model. Findings typically show that enrichment leads to increased cortical thickness. However, generalization from rats to humans must be made cautiously, as human cognition involves greater sociocultural complexity. This demonstrates the utility of animal research by providing a comparative biological basis for the hypothesis that the innovation hub's features physically "enrich" the human brain.