Obligatory “expectations” of expressive timing induced by perception of musical structure

Previous research has shown that, in a task requiring the detection of local deviations from mechanically precise timing in music, the relative detectability of deviations in different positions is closely related to the typical expressive timing pattern musicians produce when playing the music. This result suggests that listeners expect to hear music expressively timed and compensate for the absence of expressive timing. Three new detection experiments shed additional light on the nature of these timing expectations in musically trained listeners. Experiment 1 shows that repeated exposure to an atypically (but not unmusically) timed performance leaves listeners' timing expectations unaffected. Experiment 2 demonstrates that the expectations do not manifest themselves when listeners merely imagine the music in synchrony with a click track. Experiment 3, however, shows that the timing expectations are fully operational when the click track is superimposed on the music. These results reveal timing “expectations” to be an obligatory consequence of the ongoing auditory perception of musical structure. Received: 5 November 1996 / Accepted: 26 February 1997     

Perceptual integration and differentiation of spectral cues for intervocalic stop consonants

The place of articulation of intervocalic stop consonants is conveyed by temporally distributed spectral information, viz, the formant transitions preceding and following the silent closure interval (VC and CV transitions). Experiment 1 shows that more than 200 msec of silent closure is needed to hear VC and CV formant transitions as separate phonemic events (geminate stops). As closure duration is reduced, these cues are integrated into a single phonemic percept, and the VC transitions become increasingly redundant (Experiments 2 and 3). VC and CV transitions conveying different places of articulation, on the other hand, are heard as separate phonemes at closure durations as short as 100 msec. If closure duration is further reduced, a single stop is heard whose place of articulation corresponds to the CV transitions (Experiment 3). Even in the absence of CV transitions, VC transitions carry little perceptual weight at very short closure durations (Experiment 4). Despite their apparent redundancy, however, the VC transitions exert a positive bias on the perception of CV transitions at very short closure durations. At closure durations beyond 100 msec, on the other hand, VC and CV transitions interact contrastively in perception and tend to be heard as different phonemes (Experiments 5 and 6). The results of these experiments suggest two different processes of temporal integration in phonetic perception, one taking place at a precategorical level, the other combining identical phoneme categories within a certain time span.     

Perception of timing is more context sensitive than sensorimotor synchronization

In three experiments, the effects of contextual temporal variation on the perception of timing and on sensorimotor synchronization were examined. Experiment 1 showed that exposure to a variably timed auditory precursor sequence reduces the detectability of deviations from isochrony in a musical test sequence. By contrast, in Experiment 2 there was only a small and transient effect of identical precursor sequences on the variability of finger taps that were synchronized with a similar test sequence. Moreover, the precursor did not impede phase error correction following deviations from isochrony in the test sequence. Experiment 3 employed a within-subjects design that required simultaneous detection of irregularities in and synchronization with nonmusical auditory sequences. Precursor variability impaired only detection, not synchronization performance. These results suggest that perception of deviations from regularity engages context-sensitive tining processes, probably related to conscious awareness, that are not involved in sensorimotor synchronization.     

Phase correction, phase resetting, and phase shifts after subliminal timing perturbations in sensorimotor synchronization.

Recent studies of synchronized finger tapping have shown that perceptually subliminal phase shifts in an auditory sequence are rapidly compensated for in the motor activity (B. H. Repp, 2000a). Experiment 1 used a continuation-tapping task to confirm that this compensation is indeed a phase correction, not an adjustment of the central timekeeper period. Experiments 2-5 revealed that this phase correction occurs even when there is no ordinary sensorimotor asynchrony--when the finger taps are in antiphase or arbitrary phase relative to the auditory sequence (Experiments 2 and 3) or when the tap coinciding with the sequence phase shift is withheld (Experiments 4 and 5). The phase correction observed in the latter conditions was instantaneous, which suggests that phase resetting occurs when the motor activity is discontinuous. A prolonged phase shift suggestive of overcompensation was observed in some conditions, which poses a challenge to pure phase correction models.     

Perceiving the numerosity of rapidly occurring auditory events in metrical and nonmetrical contexts

Experiment 1 determined the fastest tempo at which participants could tap in synchrony with every nth tone (n = 2 to 9) in an isochronous sequence. Tapping was difficult with every 5th or 7th tone but easy with every 2nd, 4th, or 8th tone, suggesting that evenly divisible groups of n tones are automatically subdivided into equal groups of 2 or 3-a form of auditory subitizing that generates metrical hierarchies commonly found in Western music. Experiments 2 and 3 sought evidence of subitizing and subdivision in timed explicit enumeration of short, rapidly presented tone sequences (n = 2 to 10). Enumeration accuracy decreased monotonically with n. Response time increased monotonically up to n = 5 or 6, but less between 2 and 3 than between 3 and 4. Thus, a single group of 2 or 3 tones perhaps can be subitized, but subdivision of larger groups into subgroups of 2 or 3 tones seems to be specific to a repetitive, metrical context.     

Pianists duet better when they play with themselves: on the possible role of action simulation in synchronization

Ensemble musicians play in synchrony despite expressively motivated irregularities in timing. We hypothesized that synchrony is achieved by each performer internally simulating the concurrent actions of other ensemble members, relying initially on how they would perform in their stead. Hence, musicians should be better at synchronizing with recordings of their own earlier performances than with others' recordings. We required pianists to record one part from each of several piano duets, and later to play the complementary part in synchrony with their own or others' recordings. The pianists were also asked to identify their own recordings. The pianists were better at synchronizing with their own than with others' performances, and they were able to recognize their own recordings. Furthermore, synchronization accuracy and recognition were correlated: Pianists who were relatively accurate at synchronizing with their own performances were also good at recognizing them. Thus, action simulation may underlie both synchronization and self-recognition.     

Detecting deviations from metronomic timing in music: Effects of perceptual structure on the mental timekeeper

The detectability of a deviation from metronomic timing—of a small local increment in interonset interval (IOI) duration—in a musical excerpt is subject to positional biases, or “timing expectations,” that are closely related to the expressive timing (sequence of IOI durations) typically produced by musicians in performance (Repp, 1992b, 1998c, 1998d). Experiment 1 replicated this finding with some changes in procedure and showed that the perception-performance correlation is not the result of formal musical training or availability of a musical score. Experiments 2 and 3 used a synchronization task to examine the hypothesis that participants’ perceptual timing expectations are due to systematic modulations in the period of a mental timekeeper that also controls perceptual-motor coordination. Indeed, there was systematic variation in the asynchronies between taps and metronomically timed musical event onsets, and this variation was correlated both with the variations in IOI increment detectability (Experiment 1) and with the typical expressive timing pattern in performance. When the music contained local IOI increments (Experiment 2), they were almost perfectly compensated for on the next tap, regardless of their detectability in Experiment 1, which suggests a perceptual-motor feed-back mechanism that is sensitive to subthreshold timing deviations. Overall, the results suggest that aspects of perceived musical structure influence the predictions of mental timekeeping mechanisms, thereby creating a subliminal warping of experienced time.     

Basing the treatment of stereotypic and self-injurious behaviors on hypotheses of their causes.

Stereotypic and self-injurious behaviors are common forms of maladaptive responding demonstrated by severely handicapped persons. Various review papers suggest that no single treatment procedure is universally effective. Although there may be many reasons for this finding, one could be that people engage in these behaviors for various reasons, and that procedures that are incompatible with the cause of the behavior are unlikely to be effective. These studies also suggest many hypotheses for the development and maintenance of these behaviors, three of which are the self-stimulation, positive reinforcement, and negative reinforcement hypotheses. The purpose of this paper was to determine whether one of these hypotheses could be matched to the cause of the behavior and used as an effective treatment procedure. We therefore compared one hypothesis with one other for 3 subjects in a three-phase study. During baseline, data were taken in two classrooms for each subject, and a judgement was made about the hypothesis most likely to be related to the cause of the behavior. During the second phase, a treatment based on that hypothesis was used in one classroom, and a treatment based on another hypothesis was used in the second classroom. During the third phase, the treatment that was most effective in the second phase was used in both classrooms. Results showed that a successful treatment program can be developed on an hypothesis of why the behavior occurred during baseline. Results are discussed in terms of supporting the argument that treatment programs should be based on a functional analysis of the behavior in its environmental context.