The speed of time

Abstract

Event Abstract Back to Event The speed of time Misha Ahrens1, 2* and Maneesh Sahani3 1 Cambridge University, United Kingdom 2 Janelia Farm Research Campus , United States 3 UCL, Gatsby Computational Neuroscience Unit, Wellcome Trust Neuroimaging Centre and Medical School, United Kingdom The content of a visual stimulus affects its perceived duration. In particular, stimuli that change rapidly generally appear to last longer than equal-duration stimuli that change more slowly. Exactly why this is, and how stimulus-driven biases interact with internal estimates of elapsed time, is not known. One possible account is that observers expect a certain rate of discrete "events" in the world (Fraisse, 1964). The rapidly changing stimuli contain more of these events per unit time, and so observers believe that more time has elapsed. We have proposed a different view as part of a general framework for psychological time estimation (Cosyne, 2008). In our account, observers have an expection regarding the temporal correlations in the environment, which they use to translate the amount by which the stimulus changes during presentation into probabilistic infomation about its duration. Here, we contrast these two accounts, showing that they make very different predictions regarding the variability of timing estimates, and testing these predictions experimentally. Internal duration estimates are known to follow a Scalar law, whereby the distribution of estimates scales in proportion to its mean (this, in turn, suggests that the variability in estimates follows a Weber law). We measured the variability of observers’ estimates of the duration of colored (i.e. space-time smoothed) Gaussian noise stimuli for a range of different true durations, and found (1) that estimates of the duration of these dynamic stimuli were less variable that estimates of the durations of static stimuli; and (2) that the Scalar law continued to hold in the presence of these random dynamic stimuli. Both models are consistent with observation (1), as the added information in the stimulus should help to reduce variability. We have previously shown that the change-based approach also yields scale-invariant estimates, and it is thus consistent with the second observation too. By contrast, we show here that the event-counting model leads to sub-Weberian growth in variability for these stimuli, and that even when combined with an internal estimate that retains the Scalar property it cannot account for observers’ behavior. Our results thus (1) provide further evidence that the reason the psychological speed of time is affected systematically by stimuli is that observers exploit these stimuli to derive additional information about the passage of time; and (2) argue against simple counting-based sources of this additional information, lending support to the idea that the information derives from more extensive knowledge of the statistics. Conference: Computational and Systems Neuroscience 2010, Salt Lake City, UT, United States, 25 Feb - 2 Mar, 2010. Presentation Type: Poster Presentation Topic: Poster session I Citation: Ahrens M and Sahani M (2010). The speed of time. Front. Neurosci. Conference Abstract: Computational and Systems Neuroscience 2010. doi: 10.3389/conf.fnins.2010.03.00066 Copyright: The abstracts in this collection have not been subject to any Frontiers peer review or checks, and are not endorsed by Frontiers. They are made available through the Frontiers publishing platform as a service to conference organizers and presenters. The copyright in the individual abstracts is owned by the author of each abstract or his/her employer unless otherwise stated. Each abstract, as well as the collection of abstracts, are published under a Creative Commons CC-BY 4.0 (attribution) licence (https://creativecommons.org/licenses/by/4.0/) and may thus be reproduced, translated, adapted and be the subject of derivative works provided the authors and Frontiers are attributed. For Frontiers’ terms and conditions please see https://www.frontiersin.org/legal/terms-and-conditions. Received: 19 Feb 2010; Published Online: 19 Feb 2010. * Correspondence: Misha Ahrens, Cambridge University, Paris, United Kingdom, mba22@cam.ac.uk Login Required This action requires you to be registered with Frontiers and logged in. To register or login click here. Abstract Info Abstract The Authors in Frontiers Misha Ahrens Maneesh Sahani Google Misha Ahrens Maneesh Sahani Google Scholar Misha Ahrens Maneesh Sahani PubMed Misha Ahrens Maneesh Sahani Related Article in Frontiers Google Scholar PubMed Abstract Close Back to top Javascript is disabled. Please enable Javascript in your browser settings in order to see all the content on this page.