Temporal productions in a variable environment: timing starts from stimulus identification rather than onset.

Timing an interval is integral in everyday life, from crossing a street or boiling an egg to playing sports and chatting with friends. In the current article, participants were asked to produce durations ranging from 500 to 1250 ms by either terminating an automatically initiated duration, or by maintaining a key press. When participants expected this production to start was manipulated using a variable foreperiod. Further, between subjects, the durations required for production were either variable or constant within a block. Together, these manipulations set up a temporally-and event-uncertain environment. When participants both initiated and terminated an interval, the uncertainty of the environment did not systematically affect productions. However, when productions were only terminated, productions were longer and given more uncertainty. While the effects of timing onset could be attributed to when a participant registers a stimulus, the effects of uncertainty with regards to what duration would be required for production indicates that participants appear to register what a stimulus is prior to initiating their timing. This finding indicates that timing may relate to when a stimulus is identified, rather than when it is first perceived. Alternatively, perhaps the onset of timing is postponed by event uncertainty.