Your move or mine? Music training and kinematic compatibility modulate synchronization with self- versus other-generated dance movement.

Motor simulation has been implicated in how musicians anticipate the rhythm of another musician's action to achieve interpersonal synchronization. Here, we investigated whether similar mechanisms govern a related form of rhythmic action: dance. We examined (1) whether synchronization with visual dance stimuli was influenced by movement agency, (2) whether music training modulated simulation efficiency, and (3) what cues were relevant for simulating the dance rhythm. Participants were first recorded dancing the basic Charleston steps paced by a metronome, and later in a synchronization task they tapped to the rhythm of their own point-light dance stimuli, stimuli of another physically matched participant or one matched in movement kinematics, and a quantitative average across individuals. Results indicated that, while there was no overall "self advantage" and synchronization was generally most stable with the least variable (averaged) stimuli, motor simulation was driven-indicated by high tap-beat variability correlations-by familiar movement kinematics rather than morphological features. Furthermore, music training facilitated simulation, such that musicians outperformed non-musicians when synchronizing with others' movements but not with their own movements. These findings support action simulation as underlying synchronization in dance, linking action observation and rhythm processing in a common motor framework.

Metrical congruency and kinematic familiarity facilitate temporal binding between musical and dance rhythms.

Although music and dance are often experienced simultaneously, it is unclear what modulates their perceptual integration. This study investigated how two factors related to music-dance correspondences influenced audiovisual binding of their rhythms: the metrical match between the music and dance, and the kinematic familiarity of the dance movement. Participants watched a point-light figure dancing synchronously to a triple-meter rhythm that they heard in parallel, whereby the dance communicated a triple (congruent) or a duple (incongruent) visual meter. The movement was either the participant's own or that of another participant. Participants attended to both streams while detecting a temporal perturbation in the auditory beat. The results showed lower sensitivity to the auditory deviant when the visual dance was metrically congruent to the auditory rhythm and when the movement was the participant's own. This indicated stronger audiovisual binding and a more coherent bimodal rhythm in these conditions, thus making a slight auditory deviant less noticeable. Moreover, binding in the metrically incongruent condition involving self-generated visual stimuli was correlated with self-recognition of the movement, suggesting that action simulation mediates the perceived coherence between one's own movement and a mismatching auditory rhythm. Overall, the mechanisms of rhythm perception and action simulation could inform the perceived compatibility between music and dance, thus modulating the temporal integration of these audiovisual stimuli.

Visual Enhancement of Illusory Phenomenal Accents in Non-Isochronous Auditory Rhythms.

Musical rhythms encompass temporal patterns that often yield regular metrical accents (e.g., a beat). There have been mixed results regarding perception as a function of metrical saliency, namely, whether sensitivity to a deviant was greater in metrically stronger or weaker positions. Besides, effects of metrical position have not been examined in non-isochronous rhythms, or with respect to multisensory influences. This study was concerned with two main issues: (1) In non-isochronous auditory rhythms with clear metrical accents, how would sensitivity to a deviant be modulated by metrical positions? (2) Would the effects be enhanced by multisensory information? Participants listened to strongly metrical rhythms with or without watching a point-light figure dance to the rhythm in the same meter, and detected a slight loudness increment. Both conditions were presented with or without an auditory interference that served to impair auditory metrical perception. Sensitivity to a deviant was found greater in weak beat than in strong beat positions, consistent with the Predictive Coding hypothesis and the idea of metrically induced illusory phenomenal accents. The visual rhythm of dance hindered auditory detection, but more so when the latter was itself less impaired. This pattern suggested that the visual and auditory rhythms were perceptually integrated to reinforce metrical accentuation, yielding more illusory phenomenal accents and thus lower sensitivity to deviants, in a manner consistent with the principle of inverse effectiveness. Results were discussed in the predictive framework for multisensory rhythms involving observed movements and possible mediation of the motor system.

Visual Timing of Structured Dance Movements Resembles Auditory Rhythm Perception.

Temporal mechanisms for processing auditory musical rhythms are well established, in which a perceived beat is beneficial for timing purposes. It is yet unknown whether such beat-based timing would also underlie visual perception of temporally structured, ecological stimuli connected to music: dance. In this study, we investigated whether observers extracted a visual beat when watching dance movements to assist visual timing of these movements. Participants watched silent videos of dance sequences and reproduced the movement duration by mental recall. We found better visual timing for limb movements with regular patterns in the trajectories than without, similar to the beat advantage for auditory rhythms. When movements involved both the arms and the legs, the benefit of a visual beat relied only on the latter. The beat-based advantage persisted despite auditory interferences that were temporally incongruent with the visual beat, arguing for the visual nature of these mechanisms. Our results suggest that visual timing principles for dance parallel their auditory counterparts for music, which may be based on common sensorimotor coupling. These processes likely yield multimodal rhythm representations in the scenario of music and dance.

Sensorimotor Synchronization with Different Metrical Levels of Point-Light Dance Movements.

Rhythm perception and synchronization have been extensively investigated in the auditory domain, as they underlie means of human communication such as music and speech. Although recent studies suggest comparable mechanisms for synchronizing with periodically moving visual objects, the extent to which it applies to ecologically relevant information, such as the rhythm of complex biological motion, remains unknown. The present study addressed this issue by linking rhythm of music and dance in the framework of action-perception coupling. As a previous study showed that observers perceived multiple metrical periodicities in dance movements that embodied this structure, the present study examined whether sensorimotor synchronization (SMS) to dance movements resembles what is known of auditory SMS. Participants watched a point-light figure performing two basic steps of Swing dance cyclically, in which the trunk bounced at every beat and the limbs moved at every second beat, forming two metrical periodicities. Participants tapped synchronously to the bounce of the trunk with or without the limbs moving in the stimuli (Experiment 1), or tapped synchronously to the leg movements with or without the trunk bouncing simultaneously (Experiment 2). Results showed that, while synchronization with the bounce (lower-level pulse) was not influenced by the presence or absence of limb movements (metrical accent), synchronization with the legs (beat) was improved by the presence of the bounce (metrical subdivision) across different movement types. The latter finding parallels the "subdivision benefit" often demonstrated in auditory tasks, suggesting common sensorimotor mechanisms for visual rhythms in dance and auditory rhythms in music.

Visual tuning and metrical perception of realistic point-light dance movements.

Humans move to music spontaneously, and this sensorimotor coupling underlies musical rhythm perception. The present research proposed that, based on common action representation, different metrical levels as in auditory rhythms could emerge visually when observing structured dance movements. Participants watched a point-light figure performing basic steps of Swing dance cyclically in different tempi, whereby the trunk bounced vertically at every beat and the limbs moved laterally at every second beat, yielding two possible metrical periodicities. In Experiment 1, participants freely identified a tempo of the movement and tapped along. While some observers only tuned to the bounce and some only to the limbs, the majority tuned to one level or the other depending on the movement tempo, which was also associated with individuals' preferred tempo. In Experiment 2, participants reproduced the tempo of leg movements by four regular taps, and showed a slower perceived leg tempo with than without the trunk bouncing simultaneously in the stimuli. This mirrors previous findings of an auditory 'subdivision effect', suggesting the leg movements were perceived as beat while the bounce as subdivisions. Together these results support visual metrical perception of dance movements, which may employ similar action-based mechanisms to those underpinning auditory rhythm perception.

Content congruency and its interplay with temporal synchrony modulate integration between rhythmic audiovisual streams.

Both lower-level stimulus factors (e.g., temporal proximity) and higher-level cognitive factors (e.g., content congruency) are known to influence multisensory integration. The former can direct attention in a converging manner, and the latter can indicate whether information from the two modalities belongs together. The present research investigated whether and how these two factors interacted in the perception of rhythmic, audiovisual (AV) streams derived from a human movement scenario. Congruency here was based on sensorimotor correspondence pertaining to rhythm perception. Participants attended to bimodal stimuli consisting of a humanlike figure moving regularly to a sequence of auditory beat, and detected a possible auditory temporal deviant. The figure moved either downwards (congruently) or upwards (incongruently) to the downbeat, while in both situations the movement was either synchronous with the beat, or lagging behind it. Greater cross-modal binding was expected to hinder deviant detection. Results revealed poorer detection for congruent than for incongruent streams, suggesting stronger integration in the former. False alarms increased in asynchronous stimuli only for congruent streams, indicating greater tendency for deviant report due to visual capture of asynchronous auditory events. In addition, a greater increase in perceived synchrony was associated with a greater reduction in false alarms for congruent streams, while the pattern was reversed for incongruent ones. These results demonstrate that content congruency as a top-down factor not only promotes integration, but also modulates bottom-up effects of synchrony. Results are also discussed regarding how theories of integration and attentional entrainment may be combined in the context of rhythmic multisensory stimuli.

Visual enhancement of auditory beat perception across auditory interference levels.

This study dealt with audiovisual rhythm perception involving an observed movement. Two experiments investigated whether a visual beat conveyed by a bouncing human point-light figure facilitated beat perception of concurrent auditory rhythms, and whether this enhancement followed a profile of multisensory integration. In Experiment 1, participants listened to three repetitions of a metrically simple rhythm and detected a perturbation in the third repetition. The rhythm was presented alone or with a visual beat in phase to it. Both conditions were presented with or without an auditory interference sequence at four increasing tempi, which served to progressively weaken the beat of the auditory rhythm. In Experiment 2, participants tapped to a regular auditory beat in the same combinations of visual beat and auditory interference. Results showed that the visual beat improved the perception of (Experiment 1) and the synchronization to (Experiment 2) the auditory rhythms. Moreover, in both experiments, visual enhancement was greater when the performance in the unisensory (auditory) conditions was poorer, consistent with the principle of inverse effectiveness. The relative multisensory gain increased as auditory performance deteriorated, except in one intermediate level. Together these results demonstrate that rhythmic visual movement aids auditory rhythm perception, which may be subserved by a perceptually integrated audiovisual beat that couples the internal motor system.

Audiovisual beat induction in complex auditory rhythms: point-light figure movement as an effective visual beat.

This study investigated whether explicit beat induction in the auditory, visual, and audiovisual (bimodal) modalities aided the perception of weakly metrical auditory rhythms, and whether it reinforced attentional entrainment to the beat of these rhythms. The visual beat-inducer was a periodically bouncing point-light figure, which aimed to examine whether an observed rhythmic human movement could induce a beat that would influence auditory rhythm perception. In two tasks, participants listened to three repetitions of an auditory rhythm that were preceded and accompanied by (1) an auditory beat, (2) a bouncing point-light figure, (3) a combination of (1) and (2) synchronously, or (4) a combination of (1) and (2), with the figure moving in anti-phase to the auditory beat. Participants reproduced the auditory rhythm subsequently (Experiment 1), or detected a possible temporal change in the third repetition (Experiment 2). While an explicit beat did not improve rhythm reproduction, possibly due to the syncopated rhythms when a beat was imposed, bimodal beat induction yielded greater sensitivity to a temporal deviant in on-beat than in off-beat positions. Moreover, the beat phase of the figure movement determined where on-beat accents were perceived during bimodal induction. Results are discussed with regard to constrained beat induction in complex auditory rhythms, visual modulation of auditory beat perception, and possible mechanisms underlying the preferred visual beat consisting of rhythmic human motions.

Adjustments of speed and path when avoiding collisions with another pedestrian.

When walking in open space, collision avoidance with other pedestrians is a process that successfully takes place many times. To pass another pedestrian (an interferer) walking direction, walking speed or both can be adjusted. Currently, the literature is not yet conclusive of how humans adjust these two parameters in the presence of an interferer. This impedes the development of models predicting general obstacle avoidance strategies in humans' walking behavior. The aim of this study was to investigate the adjustments of path and speed when a pedestrian is crossing a non-reactive human interferer at different angles and speeds, and to compare the results to general model predictions. To do so, we designed an experiment where a pedestrian walked a 12 m distance to reach a goal position. The task was designed in such a way that collision with an interferer would always occur if the pedestrian would not apply a correction of movement path or speed. Results revealed a strong dependence of path and speed adjustments on crossing angle and walking speed, suggesting local planning of the collision avoidance strategy. Crossing at acute angles (i.e. 45° and 90°) seems to require more complex collision avoidance strategies involving both path and speed adjustments than crossing at obtuse angles, where only path adjustments were observed. Overall, the results were incompatible with predictions from existing models of locomotor collision avoidance. The observed initiations of both adjustments suggest a collision avoidance strategy that is temporally controlled. The present study provides a comprehensive picture of human collision avoidance strategies in walking, which can be used to evaluate and adjust existing pedestrian dynamics models, or serve as an empirical basis to develop new models.

Peak velocity as a cue in audiovisual synchrony perception of rhythmic stimuli.

This study investigated audiovisual synchrony perception in a rhythmic context, where the sound was not consequent upon the observed movement. Participants judged synchrony between a bouncing point-light figure and an auditory rhythm in two experiments. Two questions were of interest: (1) whether the reference in the visual movement, with which the auditory beat should coincide, relies on a position or a velocity cue; (2) whether the figure form and motion profile affect synchrony perception. Experiment 1 required synchrony judgment with regard to the same (lowest) position of the movement in four visual conditions: two figure forms (human or non-human) combined with two motion profiles (human or ball trajectory). Whereas figure form did not affect synchrony perception, the point of subjective simultaneity differed between the two motions, suggesting that participants adopted the peak velocity in each downward trajectory as their visual reference. Experiment 2 further demonstrated that, when judgment was required with regard to the highest position, the maximal synchrony response was considerably low for ball motion, which lacked a peak velocity in the upward trajectory. The finding of peak velocity as a cue parallels results of visuomotor synchronization tasks employing biological stimuli, suggesting that synchrony judgment with rhythmic motions relies on the perceived visual beat.

A unique visual rhythm does not pop out.

We investigated attentional demands in visual rhythm perception of periodically moving stimuli using a visual search paradigm. A dynamic search display consisted of vertically "bouncing dots" with regular rhythms. The search target was defined by a unique visual rhythm (i.e., a shorter or longer period) among rhythmic distractors with identical periods. We found that search efficiency for a faster or a slower periodically moving target decreased as the number of distractors increased, although searching for a faster target was about one second faster than searching for a slower target. We conclude that perception of a visual rhythm defined by a unique period is not a "pop-out" process, but a serial one that demands considerable attention.

Sensorimotor synchronization: a review of recent research (2006-2012).

Sensorimotor synchronization (SMS) is the coordination of rhythmic movement with an external rhythm, ranging from finger tapping in time with a metronome to musical ensemble performance. An earlier review (Repp, 2005) covered tapping studies; two additional reviews (Repp, 2006a, b) focused on music performance and on rate limits of SMS, respectively. The present article supplements and extends these earlier reviews by surveying more recent research in what appears to be a burgeoning field. The article comprises four parts, dealing with (1) conventional tapping studies, (2) other forms of moving in synchrony with external rhythms (including dance and nonhuman animals' synchronization abilities), (3) interpersonal synchronization (including musical ensemble performance), and (4) the neuroscience of SMS. It is evident that much new knowledge about SMS has been acquired in the last 7 years.

Body movement enhances the extraction of temporal structures in auditory sequences.

Auditory and motor systems interact in processing auditory rhythms. This study investigated the effect of intuitive body movement, such as head nodding or foot tapping, on listeners' ability to entrain to the pulse of an auditory sequence. A pulse-finding task was employed using an isochronous sequence of tones in which tones were omitted at pseudorandom positions. Musicians and non-musicians identified their subjectively fitting pulse either using periodic body movement or through listening only. The identified pulse was measured subsequently by finger tapping. Movement appeared to assist pulse extraction especially for non-musicians. The chosen pulse tempi tended to be faster with movement. Additionally, movement led to higher synchronization stabilities of the produced pulse along the sequence, regardless of musical training. These findings demonstrated the facilitatory role of body movement in entraining to auditory rhythms and its interaction with musical training.

Hearing the speed: visual motion biases the perception of auditory tempo.

The coupling between sensory and motor processes has been established in various scenarios: for example, the perception of auditory rhythm entails an audiomotor representation of the sounds. Similarly, visual action patterns can also be represented via a visuomotor transformation. In this study, we tested the hypothesis that the visual motor information, such as embedded in a coherent motion flow, can interact with the perception of a motor-related aspect in auditory rhythm: the tempo. In the first two experiments, we employed an auditory tempo judgment task where participants listened to a standard auditory sequence while concurrently watching visual stimuli of different motion information, after which they judged the tempo of a comparison sequence related to the standard. In Experiment 1, we found that the same auditory tempo was perceived as faster when it was accompanied by accelerating visual motion than by non-motion luminance change. In Experiment 2, we compared the perceived auditory tempo among three visual motion conditions, increase in speed, decrease in speed, and no speed change, and found the corresponding bias in judgment of auditory tempo: faster than it was, slower than it was, and no bias. In Experiment 3, the perceptual bias induced by the change in motion speed was consistently reflected in the tempo reproduction task. Taken together, these results indicate that between a visual spatiotemporal and an auditory temporal stimulation, the embedded motor representations from each can interact across modalities, leading to a spatial-to-temporal bias. This suggests that the perceptual process in one modality can incorporate concurrent motor information from cross-modal sensory inputs to form a coherent experience.