Tryon’s Rat Experiment is a multi-decade selective breeding animal experiment begin in the 1930s which rapidly bred enormous differences in a complex psychological trait, maze-running, demonstrating core principles of behavior genetics.
Tryon’s Rat Experiment is a multi-decade selective breeding animal experiment in the 1920s–1940s which employed automated maze-running machinery to minimize measurement error and, using truncation selection, bred two different strains of rats: “maze-bright” and “maze-dull” rats, selected for high & low maze-running performance.
Within a few generations, the rats showed increasing differences in maze-running performance, and the two strains eventually had non-overlapping distributions. Tryon’s Rat Experiment rapidly bred enormous differences in a complex psychological trait, demonstrating core principles of behavior genetics: the heritability of even psychological traits far removed from standard examples of genetics like coat color, and the ability of selection produce large population-wide changes in a short time for even highly polygenic traits like maze-running.
The etiology of the changes in performance were subsequently investigated: the performance changes were not on the g-factor of intelligence, but were more maze-running-specific, and have neurological correlates.
The experiment was widely-cited in psychology and early behavior genetics, and paralleled various later experiments in selection on complex behavioral traits.