Stimulus variation and sequential judgements of duration

When a series of reproductions of an interval is made in the absence of a standard the judgements progressively lengthen. The similarity between stimulus conditions in this type of time estimation experiment and the conditions which produce a decrement in human vigilance is discussed. It is argued that failure to detect cues for the passage of time reduces the amount of time perceived to elapse. Reproduced judgements must consequently be increased in length to match remembered standards. The hypothesis is then made that the kind of variation in background stimulation which facilitates vigilance should increase the frequency of detection of cues for duration and reduce reproduced judgements. This hypothesis is tested with 80 subjects and a reversal of the serial reproduction effect is found on trials with changed background conditions.