Slowing down an internal clock: implications for accounts of performance on four timing tasks.

An experiment investigated the potential effects of lowering arousal on performance on time perception tasks. Four participant groups received different tasks: Normal and episodic temporal generalization, bisection, and verbal estimation, all involving judgements of the duration of visual stimuli. Self-rated arousal during the experimental session was lowered by spacing experimental trials approximately 10 s apart. Between the early and late blocks of the experiment, performance changed on normal temporal generalization and verbal estimation, but not on episodic temporal generalization and bisection. The changes were consistent with the idea that the pacemaker of the participant's internal clock had been slowed down by the slow trial spacing. Results suggested that bisection was based on a criterion that adjusted during the experiment, whereas verbal estimation was based on preexisting standards, or those established early in the experiment.