Temporal Regularity of the Environment Drives Time Perception

Repertoire of timescales in uni - and transmodal regions mediate working memory capacity

Working memory (WM) describes the dynamic process of maintenance and manipulation of information over a certain time delay. Neuronally, WM recruits a distributed network of cortical regions like the visual and dorsolateral prefrontal cortex as well as the subcortical hippocampus. How the input dynamics and subsequent neural dynamics impact WM remains unclear though. To answer this question, we combined the analysis of behavioral WM capacity with measuring neural dynamics through task-related power spectrum changes, e.g., median frequency (MF) in functional magnetic resonance imaging (fMRI). We show that the processing of the input dynamics, e.g., the task structure's specific timescale, leads to changes in the unimodal visual cortex's corresponding timescale which also relates to working memory capacity. While the more transmodal hippocampus relates to working memory capacity through its balance across multiple timescales or frequencies. In conclusion, we here show the relevance of both input dynamics and different neural timescales for WM capacity in uni - and transmodal regions like visual cortex and hippocampus for the subject's WM performance.

Interval timing in a hierarchical violation-of-expectation task: Dissociable effects of local and global predictions

Predictability associated with an event influences its perceived time. The two forms of predictions that are often discussed and have a dissociable influence on perceived time are repetition and expectation. However, predictions based on expectation can be seen at multiple levels, potentially leading to an inconsistency in the pattern in which expectation influences perceived time. Therefore, the present study aimed to investigate how different levels of predictions impact perceived time. In two separate experiments utilizing visual and auditory stimuli, we used a hierarchical violation-of-expectation paradigm that can dissociate two types of predictions based on local and global rules. Results from analysis of variance computed with local and global predictions revealed a pattern of local and global predictions having a distinct influence on perceived time. More specifically, while the local predictions that consider the immediate stimulus exposure reduced the perceived time, the global predictions that consider the overall regularities of a given context increased the perceived time. These results integrate well with the recent theoretical models rooted in a predictive coding framework that emphasizes the opposing effects of the first order and second order predictions on perceived time.

Reducing the tendency for chronometric counting in duration discrimination tasks

Chronometric counting is a prevalent issue in the study of human time perception as it reduces the construct validity of tasks and can conceal existing timing deficits. Several methods have been proposed to prevent counting strategies, but the factors promoting those strategies in specific tasks are largely uninvestigated. Here, we modified a classical two-interval duration discrimination task in two aspects that could affect the tendency to apply counting strategies. We removed the pause between the two intervals and changed the task instructions: Participants decided whether a short event occurred in the first or in the second half of a reference duration. In Experiment 1, both classical and modified task versions were performed under timing conditions, in which participants were asked not to count, and counting conditions, in which counting was explicitly instructed. The task modifications led to (i) a general decrease in judgment precision, (ii) a shift of the point of subjective equality, and (iii) a counting-related increase in reaction times, suggesting enhanced cognitive effort of counting during the modified task version. Precision in the two task versions was not differently affected by instructed counting. Experiment 2 demonstrates that—in the absence of any counting-related instructions—participants are less likely to engage in spontaneous counting in the modified task version. These results enhance our understanding of the two-interval duration discrimination task and demonstrate that the modifications tested here—although they do not significantly reduce the effectiveness of instructed counting—can diminish the spontaneous tendency to adopt counting strategies.

The implicit sense of agency is not a perceptual effect but is a judgment effect

The sense of agency (SoA) is characterized as the sense of being the causal agent of one's own actions, and it is measured in two forms: explicit and implicit. In the explicit SoA experiments, the participants explicitly report whether they have a sense of control over their actions or whether they or somebody else is the causal agent of seen actions; the implicit SoA experiments study how do participants' agentive or voluntary actions modify perceptual processes (like time, vision, tactility, and audition) without directly asking the participants to explicitly think about their causal agency or sense of control. However, recent implicit SoA literature reported contradictory findings of the relationship between implicit SoA reports and agency states. Thus, I argue that the purported implicit SoA reports are not agency-driven perceptual effects per se but are judgment effects, by showing that (a) the typical operationalizations in implicit SoA domain lead to perceptual uncertainty on the part of the participants, (b) under uncertainty, participants' implicit SoA reports are due to heuristic judgments which are independent of agency states, and (c) under perceptual certainty, the typical implicit SoA reports might not have occurred at all. Thus, I conclude that the instances of implicit SoA are judgments (or response biases)-under uncertainty-rather than perceptual effects.

Discrimination of Regular and Irregular Rhythms Explained by a Time Difference Accumulation Model

Perceiving the temporal regularity in a sequence of repetitive sensory events facilitates the preparation and execution of relevant behaviors with tight temporal constraints. How we estimate temporal regularity from repeating patterns of sensory stimuli is not completely understood. We developed a decision-making task in which participants had to decide whether a train of visual, auditory, or tactile pulses, had a regular or an irregular temporal pattern. We tested the hypothesis that subjects categorize stimuli as irregular by accumulating the time differences between the predicted and observed times of sensory pulses defining a temporal rhythm. Results suggest that instead of waiting for a single large temporal deviation, participants accumulate timing-error signals and judge a pattern as irregular when the amount of evidence reaches a decision threshold. Model fits of bounded integration showed that this accumulation occurs with negligible leak of evidence. Consistent with previous findings, we show that participants perform better when evaluating the regularity of auditory pulses, as compared with visual or tactile stimuli. Our results suggest that temporal regularity is estimated by comparing expected and measured pulse onset times, and that each prediction error is accumulated towards a threshold to generate a behavioral choice.

Temporal bisection is influenced by ensemble statistics of the stimulus set

Although humans are well capable of precise time measurement, their duration judgments are nevertheless susceptible to temporal context. Previous research on temporal bisection has shown that duration comparisons are influenced by both stimulus spacing and ensemble statistics. However, theories proposed to account for bisection performance lack a plausible justification of how the effects of stimulus spacing and ensemble statistics are actually combined in temporal judgments. To explain the various contextual effects in temporal bisection, we develop a unified ensemble-distribution account (EDA), which assumes that the mean and variance of the duration set serve as a reference, rather than the short and long standards, in duration comparison. To validate this account, we conducted three experiments that varied the stimulus spacing (Experiment 1), the frequency of the probed durations (Experiment 2), and the variability of the probed durations (Experiment 3). The results revealed significant shifts of the bisection point in Experiments 1 and 2, and a change of the sensitivity of temporal judgments in Experiment 3-which were all well predicted by EDA. In fact, comparison of EDA to the extant prior accounts showed that using ensemble statistics can parsimoniously explain various stimulus set-related factors (e.g., spacing, frequency, variance) that influence temporal judgments.

Temporal Context affects interval timing at the perceptual level

There is now ample evidence that when observers are asked to estimate features of an object they take into account recent stimulation history and blend the current sensory evidence with the recent stimulus intensity according to their reliability. Most of this evidence has been obtained via estimation or production paradigms both of which entail a conspicuous post-perceptual decision stage. So it is an unsolved question, as to whether the trace of previous stimulation contributes at the decision stage or as early as the perceptual stage. To this aim we focused on duration judgments, which typically exhibit strong central tendency effects and asked a duration comparison between two intervals, one of which characterized by high uncertainty. We found that the perceived duration of this interval regressed toward the average duration, demonstrating a genuine perceptual bias. Regression did not transfer between the visual and the auditory modality, indicating it is modality specific, but generalized across passively observed and actively produced intervals. These findings suggest that temporal central tendency effects modulate how long an interval appears to us and that integration of current sensory evidence can occur as early as in the sensory systems.

The Effect of a Regular Auditory Context on Perceived Interval Duration

In the auditory domain, the perceived duration of time intervals is influenced by background sounds - the auditory context in which the intervals are embedded - even when the background may be ignored. Previous research has shown that a regular context made of evenly spaced sounds improves participants' discrimination of intervals close in duration to the context intervals. These results have been explained in terms of attention and anticipation. The present study reconsiders the effect of context regularity, focusing on the relationships among the intervals in the context and the interval to be estimated. The influence of a regular compared to a non-regular auditory context on interval discrimination was examined with a two interval forced choice task, which required participants to discriminate between the durations of two time intervals. Duration perception was more precise when the intervals to be discriminated were preceded by a regular compared to a non-regular context. This effect of the regular context, however, was not selective for the duration of the first interval to be estimated, contrary to suggestions based on previous evidence.

Seeking Temporal Predictability in Speech: Comparing Statistical Approaches on 18 World Languages

Temporal regularities in speech, such as interdependencies in the timing of speech events, are thought to scaffold early acquisition of the building blocks in speech. By providing on-line clues to the location and duration of upcoming syllables, temporal structure may aid segmentation and clustering of continuous speech into separable units. This hypothesis tacitly assumes that learners exploit predictability in the temporal structure of speech. Existing measures of speech timing tend to focus on first-order regularities among adjacent units, and are overly sensitive to idiosyncrasies in the data they describe. Here, we compare several statistical methods on a sample of 18 languages, testing whether syllable occurrence is predictable over time. Rather than looking for differences between languages, we aim to find across languages (using clearly defined acoustic, rather than orthographic, measures), temporal predictability in the speech signal which could be exploited by a language learner. First, we analyse distributional regularities using two novel techniques: a Bayesian ideal learner analysis, and a simple distributional measure. Second, we model higher-order temporal structure—regularities arising in an ordered series of syllable timings—testing the hypothesis that non-adjacent temporal structures may explain the gap between subjectively-perceived temporal regularities, and the absence of universally-accepted lower-order objective measures. Together, our analyses provide limited evidence for predictability at different time scales, though higher-order predictability is difficult to reliably infer. We conclude that temporal predictability in speech may well arise from a combination of individually weak perceptual cues at multiple structural levels, but is challenging to pinpoint.

Correction: Temporal Regularity of the Environment Drives Time Perception

[This corrects the article DOI: 10.1371/journal.pone.0159842.].