Emotion Effects on Timing: Attention versus Pacemaker Accounts Ming Ann Lui1,2, Trevor B. Penney1, Annett Schirmer1* 1 Department of Psychology, National University of Singapore, Singapore, Singapore, 2 Institute of Cognitive Neuroscience, National Central University, Jhongli City, Taiwan Abstract Emotions change our perception of time. In the past, this has been attributed primarily to emotions speeding up an ‘‘internal clock’’ thereby increasing subjective time estimates. Here we probed this account using an S1/S2 temporal discrimination paradigm. Participants were presented with a stimulus (S1) followed by a brief delay and then a second stimulus (S2) and indicated whether S2 was shorter or longer in duration than S1. We manipulated participants’ emotions by presenting a task-irrelevant picture following S1 and preceding S2. Participants were more likely to judge S2 as shorter than S1 when the intervening picture was emotional as compared to neutral. This effect held independent of S1 and S2 modality (Visual: Exps. 1, 2, & 3; Auditory: Exp. 4) and intervening picture valence (Negative: Exps. 1, 2 & 4; Positive: Exp. 3). Moreover, it was replicated in a temporal reproduction paradigm (Exp. 5) where a timing stimulus was preceded by an emotional or neutral picture and participants were asked to reproduce the duration of the timing stimulus. Taken together, these findings indicate that emotional experiences may decrease temporal estimates and thus raise questions about the suitability of internal clock speed explanations of emotion effects on timing. Moreover, they highlight attentional mechanisms as a viable alternative. Citation: Lui MA, Penney TB, Schirmer A (2011) Emotion Effects on Timing: Attention versus Pacemaker Accounts. PLoS ONE 6(7): e21829. doi:10.1371/ journal.pone.0021829 Editor: Warren H. Meck, Duke University, United States of America Received February 3, 2011; Accepted June 9, 2011; Published July 20, 2011 Copyright: 2011 Lui et al. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. Funding: This research was supported by the NUS Young Investigator Award conferred to Annett Schirmer (R581-000-066-101) and the Taiwan National Science Council Grants (NSC 98-2410-H-008 -082 & NSC 99-2410-H-008 -029) awarded to Ming Lui. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript. Competing Interests: The authors have declared that no competing interests exist. * E-mail: schirmer@nus.edu.sg Introduction In an effort to distinguish man from beast, ancient philosophers dissociated thought from passion and attributed thought to the workings of the brain and passion to the workings of other bodily organs [1]. Although research since then has demonstrated thought in non-human animals and identified the brain as the substrate for both thought and the subjective feeling state called emotion [2], it is only recently that putative interactions between emotions and various cognitive functions have been subject to significant research (for a review see [3]). This work demonstrated that emotions facilitate perceptual processing by lowering the threshold for awareness [4]; items of emotional relevance to the observer are more likely to be noticed than are neutral items. Emotions have also been found to influence memory [5]; images and verbal information are better remembered if they are emotional as compared to neutral [6–8]. Furthermore, there is evidence for emotions affecting language. Positive emotional states enhance the spread of activation among associatively linked words in semantic memory making it easier for individuals to relate these words and to generate ideas based on their perceived relationship [9]. Amidst the growth of studies on the interaction between emotion and cognition, insights into the role of emotions on interval timing have remained limited. Interval timing typically refers to our capacity to monitor and store durations in the hundreds of milliseconds to minutes range and to adjust our behavior based on these durations. For example, we may have a stored temporal representation of how long it takes for someone to answer a knock at their door. Thus, if a person fails to open the door within that time period, we will not continue knocking indefinitely, but will instead move on once the evoked temporal representation has elapsed. Sensitivity to time is a fundamental aspect of many higher order cognitive processes including decision making, memory and language (for a review see [10]). As such it has been a vivid area of research resulting in a number of interval timing models. The most influential model to date is Scalar Expectancy Theory (SET) [11]. The information-processing version of SET [12] postulates clock, memory, and decision stages. When timing the duration of an event, pulses from a pacemaker accumulate to form a temporal representation of the currently elapsing duration. This temporal representation is compared with duration representations previously stored in memory and behavior results when the current interval exceeds some threshold of similarity to the remembered interval. According to this model, interval timing taps a range of cognitive functions including perception, attention, and memory. Thus, when considering the potential influence of emotions on interval timing, the relationship between emotions and these functions may prove critical. An indication of a role for emotions in time perception comes from both linguistics and timing experiments. The saying ‘‘time drags’’ is typically used in the context of negative or boring events, whereas the saying ‘‘time flies’’ is used in the context of positive or exciting events [13–14]. Thus, one may infer that positive emotions lead to an underestimation of duration, whereas negative PLoS ONE | www.plosone.org 1 July 2011 | Volume 6 | Issue 7 | e21829