Measuring perceptual centers using the phase correction response Rudi C. Villing & Bruno H. Repp & Tomas E. Ward & Joseph M. Timoney Published online: 24 March 2011 # Psychonomic Society, Inc. 2011 Abstract The perceptual center (P-center) is fundamental to the timing of heterogeneous event sequences, including music and speech. Unfortunately, there is currently no comprehensive and reliable model of P-centers in acoustic events, so P-centers must instead be measured empirically. This study reviews existing measurement methods and evaluates two methods in detail—the rhythm adjustment method and a new method based on the phase correction response (PCR) in a synchro- nous tapping task. The two methods yielded consistent P-center estimates and showed no evidence of P-center context dependence. The PCR method appears promising because it is accurate and efficient and does not require explicit perceptual judgments. As a secondary result, the magnitude of the PCR is shown to vary systematically with the onset complexity of speech sounds, which presumably reflects the perceived clarity of a sound’s P-center. Keywords Temporal processing . Perceptual center (P-center) . Phase correction response (PCR) . Sensorimotor synchronization The fundamental nature of the perceptual center (P-center) may be recognized in its relationship to the elementary temporal perceptions of simultaneity, successiveness, tem- poral order, and interval duration (Pöppel, 1997) and to the higher level perception of temporal patterns, including rhythm. The P-center is the hypothetical specific moment at which a brief event is perceived to occur (Morton, Marcus, & Frankish, 1976). From this definition, it follows that when two such events are synchronized, it is their P-centers that are (approximately) synchronous, and when a sequence of events occurs, it is the pattern of P-centers that determines the perceived sequence timing: rhythmic (regular and predictable) or arrhythmic (unpredictable) and expres- sively or mechanically timed. But what is an event? An event may be defined as a segment of time that an observer conceives as having a beginning and an end (Zacks & Tversky, 2001); the description and identity of the event result from some integration of the sensations and perceptions that occur during its span. Segmenting continuous experience into discrete events appears to be an important ongoing compo- nent of perception (Kurby & Zacks, 2008; Zacks, Speer, Swallow, Braver, & Reynolds, 2007). P-centers are important mainly for events and intervals that are directly sensed, rather than remembered, and take place within the timescale of the psychological present, or about 3 s (see, e.g., Fraisse, 1984; Pöppel, 1997). Furthermore, the P-center concept is applica- ble primarily to events that are perceived to occur at rather well-defined times—for example, musical tones, speech syllables, visual flashes, and dance movements. Unfortunately, no single, well-defined, objectively mea- surable time point of an event has yet been found that reliably corresponds to the P-center. In the auditory modality, for example, rejected candidate time points include the acoustic onset (Morton et al., 1976), absolute or relative onset thresholds (Gordon, 1987), local or global intensity peaks (Gordon, 1987; Marcus, 1981), and the measured vowel onset in syllables (Marcus, 1981). There is an important consequence of the mismatch between the empirically determined P-center and any easily measurable time point of an event: The perceptual timing of a R. C. Villing (*) : T. E. Ward : J. M. Timoney National University of Ireland Maynooth, Maynooth, Ireland e-mail: rudi.villing@nuim.ie B. H. Repp Haskins Laboratories, New Haven, CT, USA Atten Percept Psychophys (2011) 73:1614–1629 DOI 10.3758/s13414-011-0110-1 1637