# Keeping the Time: The Impact of External Clock-Speed Manipulation on Time-Based Prospective Memory

## TL;DR

This study explores how manipulating clock speed affects people's ability to monitor time for future tasks, suggesting they track time by counting clock digits.

## Contribution

The study provides new evidence that people use numerical progression of clock ticks to track target times for prospective memory.

## Key findings

- Participants in the slower clock condition increased time monitoring in the second TBPM block.
- Participants in the faster clock condition checked the clock less frequently during the 4th minute.
- TBPM performance was not affected by clock-speed manipulation.

## Abstract

Several studies have suggested that time monitoring is important for appropriate time-based prospective memory (TBPM). However, it is still unknown if people actively use internal timing processes to monitor the approaching target time, and whether they do so by tracking the duration between clock digits, or by counting and matching the numerical progression of clock ticks’ digits with the target time. Therefore, in the present study, we investigated whether a manipulation of the external time affected time monitoring and TBPM performance. In two experiments, participants performed two identical TBPM tasks: a first TBPM block with no clock-speed manipulation followed by a second TBPM block, where the clock-speed was manipulated as faster or slower (experimental conditions) or normal (control condition). The results showed that only participants in the slower clock condition increased time monitoring in the second compared to the first TBPM block (d = 0.42 and 1.70); moreover, particularly in Experiment 2, participants in the faster clock condition checked the clock significantly less frequently than participants in the slower clock (d = –1.70) and in the control condition (d = –0.98), but only during the 4th minute. No effect was found for TBPM performance. Overall, results suggested that people tracked the target time by counting and matching the numerical progression of clock ticks’ digits with the target time. The findings are discussed considering the most recent theoretical advancements about the relationship between time perception and TBPM.