The Location Effect In Endogenous Temporal Expectation

A frontier topic in cognitive psychology is how human beings process the lapse of perceived time implicitly. Recently, studies had demonstrated different types of implicit timing due to various non-temporal tasks used. However, so far, there is lack of systematic investigation on issue such as whether implicit timing shares similar mechanisms of temporal pulse accumulation and attentional modulation as explicit timing. Location effect was widely found in explicit time perception in that different locations of the non-temporal task can modulate the length of the perceived time. Our study intended to explore whether there was a similar location effect in endogenous temporal expectation which is a signature of the mechanism of temporal pulse accumulation and whether there was an effect of processing demand of a non-temporal task which is predicted by the framework of attentional sharing and shifting.In our study, all of three experiments use a temporal orienting task and a pitch discrimination task. The temporal orienting task ask participants to respond to the targeted stimulus as soon as possible. A symbolic cue before the target presentation was used to predict specifically a short or a long time interval before the target, which was effective in most cases. The pitch discrimination task ask participants to distinguish sounds ("high" or "low") which appeared within the pre-cued interval. In the experiment 1, participants were required to complete a single task and a dual-task in turn. The results showed that participants’RTs increased significantly as the position of the pitch discrimination task became closer to the target, a location effect similar to that found in explicit time perception. It is likely that attention was directed away from time processing for a longer time when the pitch discrimination appeared later, resulting in a greater number of temporal pulse lost and a subsequent less-accurate estimation of temporal expectation. In addition, experiment 1 showed that the temporal expectation could be found in the interval of more than 2s:A temporal orienting effect was found in both single and dual-tasks but the effects of cue validity were significantly greater in the single task than those in the dual-task. Sequence effect was found in both single and dual-tasks, and were not significantly different between the single and the dual-task. In order to explore whether the location effect was induced by automatic shifts that are triggered by a stimulus that is completely irrelevant to the experimental task, we designed the experiment 2. In the experiment 2, participants were required to complete a single task and an ignore-task in turn. The results showed that a significant location effect in the ignore condition. However, we found that the location effect was stronger in the process condition in the experiment 1 than in the ignore condition in the experiment 2. We could not rule out the effect of the automatic shifts, but the effect was weak. We designed the experiment 3 to investigate whether the location effect was derived from the attentional modulation mechanism. In experiment 3, participants were asked to complete two dual-tasks successively. The temporal orienting task was same between the two dual-tasks, but the difficulty of the pitch discrimination task was different. The results showed that the location effect was stronger as the non-temporal task was more difficult. So it revealed that there is an attentional modulation mechanism in implicit timing.Our results revealed in the first time both a location effect in endogenous temporal expectation, providing strong evidence to the idea that implicit time perception shares similar mechanisms of both temporal pulse accumulation and attentional modulation, as those in explicit time perception.