Do Monkeys' Subjective Clocks Run Faster in Red Light than in Blue?

When monkeys are given control of the illumination in a testing chamber, it has been found, under three conditions, that they spend less time with red light than with blue. But the results cannot easily be explained in terms of ‘preference’. Rather, the results suggest that monkeys judge ‘subjective time’ to pass nearly twice as fast in red light as in blue.