Investing the 'time' in time-based prospective memory

Time-based (TB) prospective memory tasks require the estimation of time in passing---known as prospective timing. Prospective timing is said to depend on an attentionally-driven internal clock mechanism, and is thought to be unaffected by memory for interval information (for a review see, Block & Zakay, 1997). A prospective timing task that required a verbal estimate following the entire interval (Experiment 1) and a TB prospective memory task that required production of a target response during the interval (Experiment 2) were used to test an alternative view that memory does influence prospective timing. In both experiments, participants performed an ongoing task for 11.02 minutes while a varying number of songs were played in the background.;Experiment 1 results revealed that participants' time estimates became longer the more songs they remembered from the interval, suggesting that memory for interval information influences prospective time estimates. In Experiment 2, participants who were asked to perform the TB prospective memory task without the aid of an external clock made their target responses earlier as the number of songs increased, indicating that estimates of elapsed time increased as more songs were experienced. For participants who had access to a clock, changes in clock-checking coincided with the occurrence of song boundaries, indicating that participants used both song information and clock information to estimate time. Finally, ongoing task performance and verbal reports in both experiments further substantiate a role for memory in prospective timing.