Abstract
Selective breeding for response duration of the lever press was practiced over 6 generations of Swiss Webster white mice. The heritability of response duration was determined as h2 = .338 ± .336 (95% confidence interval) under H o ∴ h2 = 0; Ho ∴ h2 ≠ 0 or h2 = .338 ± .228 (95% confidence interval) under Ho ∴ h3 = 0; H ∴ h2 > 0. In maze running tests short-response-duration mice made fewer errors and took less time to learn a problem to criterion than did long response-duration animals. Rats bred at another laboratory for maze intelligence and tested here for response duration analogously had short duration lever responses when they were maze-bright and long duration responses when they were maze-dull.
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