© Koninklijke Brill NV, Leiden, 2018 DOI: 10.1163/22134468-00002098 Timing & Time Perception 6 (2018) 14–31 brill.com/time Effect of Acute Physical Activity on Interval Timing Ceyda Sayalı1 , 4, Ezgi Uslu1, Melisa Menceloğlu1 , 5, Reşit Canbeyli2 and Fuat Balcı1 , 3 , * 1Department of Psychology, Koc University, Rumelifeneri Yolu, Sarıyer, Istanbul 34450, Turkey 2Department of Psychology, Bogaziçi University, Istanbul 34342, Turkey 3Koç University Research Center for Translational Medicine, Istanbul 34450, Turkey 4Present address: Brown University Department of Cognitive, Linguistic & Psychological Sciences, Providence, RI 02912, USA 5Present address: Northwestern University, Department of Psychology, Evanston, IL 60208, USA Received 16 October 2016; accepted 6 December 2017 Abstract Timing is an integral part of physical activities. Walking as a routine form of physical activity might affect interval timing primarily in two different ways within the pacemaker–accumulator timing- theoretic framework: (1) by increasing the speed of the pacemaker due to its physiological effects; (2) by decreasing attention to time and consequently slowing the rate of temporal integration by serving as a secondary task. In order to elucidate the effect of movement on subjective time, in two different experiments we employed a temporal reproduction task conducted on the treadmill under four different encoding–decoding conditions: (1) encoding and reproducing (decoding) the duration while standing (rest); (2) encoding the duration at rest and reproducing it while mov- ing: (3) both encoding and reproducing the duration while moving; and (4) encoding the duration while moving and reproducing it at rest. In the first experiment, participants were tested either in the 4 or the 8 km/h movement condition, whereas in the second experiment a larger sample was tested only in the 4 km/h movement condition. Data were de-trended to control for long-term per- formance drifts. In Experiment 1, overall durations encoded at rest and reproduced during motion were under-reproduced whereas durations encoded during motion and reproduced at rest were over-reproduced only in the 8 km/h condition. In Experiment 2, the same results were observed in the 4 km/h condition with a larger sample size. These effects on timing behavior provide support for the clock speed-driven effect of movement and contradicts the predictions of attention-based mediation. Keywords Temporal reproduction, physical activity, movement, attentional-gate model, internal clock, pacemaker–accumulator model * To whom correspondence should be addressed. E-mail: fbalci@ku.edu.tr