PSYCHOPHYSIOLOGY Vol. 28, No. 6 Copyright © 1991 by The Society for Psychophysiological Research, Inc. Printed in U.S.A. The Processing of Temporal Intervals Reflected by CNV-Like Brain Potentials THOMAS ELBERT', ROLF ULRICH^, BRIGITTE ROCKSTROH^, AND WERNER LUTZENBERGER^ 'Institutfur Experimentelle Audiologie, Universitdt MUnster, 'Psychologisches Institut, Eberhard-Karls-Universitdt, Tubingen, and ^Psychologisches Institut, Universitat Konstanz, Germany ABSTRACT The present study employed event-related potentials (ERPs) of the hrain to improve the understanding of temporal processing. A reproduction paradigm was realized by presenting a visual stimulus (illuminated screen) for intervals of varying length. A few seconds after presentation of such standard intervals the visual stimulus was switched on again and subjects were asked to reproduce the duration of the standard interval by turning off the illumination after a corresponding interval had elapsed. The length of standard intervals varied randomly with each of the following lengths being presented 20 times: 1, 2, 3, 4, 6, and 8 s. Reproduction was accurate for standard intervals up to 3 s but deteriorated with increasing interval length. Brain potentials during reproduction intervals of 1-3 s differed from those recorded during the longer intervals. A CNV-like slow negative shift developed during the shorter reproduction intervals. Negativity was reduced or even absent, when subjects had to reproduce standard intervals of 4 s or longer. The ERP results suggest that intervals shorter than 3-4 s may evoke a processing mode that is qualitatively different from the one dominating when periods in the range of several seconds have to be processed. DESCRIPTORS: CNV, Event-related potentials. Time perception. Preparatioti of efficietit behavior, for example, Fraisse (1984), in his review, distinguishes for a fast response, certainly benefits from predict- amotig the perception of instantaneity for intervals ing precisely the point in time when a coming event up to 100 ms, perception of duration in the present would require a response. Consequently, processing for intervals between 100 ms and less than 5 s, and of temporal information can be considered a rele- perception of duration involving memory for long- vant part of response preparation. er intervals, typically exceeding 5 s. Indeed, a num- Temporal processing such as perception and es- ber of findings suggest different types of processing timation of time during short intervals has been for short and longer time intervals. It has been re- studied for more than a century. In the commonly peatedly documented that intervals up to 3-s du- used "reproduction paradigm" subjects are asked ration are reproduced with considerable precision, to reproduce time intervals that have been pre- whereas the variability of reproduction increases sented a short time earlier. Although this research for intervals exceeding 3-4 s (Vierordt, 1868; has provided hypothetical models of time estima- Woodrow, 1930; Thomas & Brown, 1974; Poppel, tion, it remains unclear which psychophysical law 1978, 1983, 1985; Fraisse, 1978). Attempts failed to governs the transformation of objective time into explain the change in reproduction quality by sim- subjective time. ply applying Weber's law, which states that the stan- dard deviation of the reproduced interval (SD(r)) should increase linearly with the duration (d) of the This research was supported by the Deutsche For- standard interval (the Weber fraction SD(r)/d = schungsgemeinschaft. const.) (reviewed by Woodrow, 1951; Allan & Kris- The authors gratefully acknowledge the assistance of toflferson, 1974; Allan, 1979). Reproduction studies Alexander Caviccioli for data collection and the helpful 1 j ..u * or-»/ \ • .. • n u «^/%t ^ „_ T.1.1- V T> • jc • revealed that SEW r) increases monotomcally but not comments of Dan Ruchkin, Kees Brunia, and Francoise ,. , . , , . _, , x^ /,r.-i,n Macar on earlier drafts of this article. linearly wtth duration. Thomas and Brown (1974) Address requests for reprints to: Prof. Dr. Brigitte even reported constancy of SD(r) for standard ln- Rockstroh, Psychologische Institut, Universitat Kon- tervals up to 1.75 s. Only for larger intervals (d>4.5 stanz, Postfach 5566, D-7750 Konstanz, Germany. s) was an augmentation of SD(r) observed with in- 648