Michael J. Richardson - Academia.edu (original) (raw)

Papers by Michael J. Richardson

Frontiers in Psychology, 2015

Understanding everyday behavior relies heavily upon understanding our ability to improvise, how w... more Understanding everyday behavior relies heavily upon understanding our ability to improvise, how we are able to continuously anticipate and adapt in order to coordinate with our environment and others. Here we consider the ability of musicians to improvise, where they must spontaneously coordinate their actions with co-performers in order to produce novel musical expressions. Investigations of this behavior have traditionally focused on describing the organization of cognitive structures. The focus, here, however, is on the ability of the time-evolving patterns of inter-musician movement coordination as revealed by the mathematical tools of complex dynamical systems to provide a new understanding of what potentiates the novelty of spontaneous musical action. We demonstrate this approach through the application of cross wavelet spectral analysis, which isolates the strength and patterning of the behavioral coordination that occurs between improvising musicians across a range of nested time-scales. Revealing the sophistication of the previously unexplored dynamics of movement coordination between improvising musicians is an important step toward understanding how creative musical expressions emerge from the spontaneous coordination of multiple musical bodies.

Biological systems are capable of acting in a shared environment to produce emergent, self-organi... more Biological systems are capable of acting in a shared environment to produce emergent, self-organized behavior that is the result of the constraints imposed by local interactions– such as bird flocking or ant swarming behavior. These examples present minimal demands for a shared-intention between co-actors, whereas other instances necessitate the formation of a shared goal. In these goal-directed tasks, how much of the observed complexity can be explained by the constraints imposed by both the environment and adherence to the shared task goal? This paper begins to investigate this question by presenting results from a two-person cooperative " shepherding " task first developed in Nalepka et al. (2017) but with fewer constraints. Results provide further evidence that the emergent behavior is the result of the constraints imposed by the task. The included task-dynamic model suggests a general model that can be used to understand multiagent herding behavior in a variety of contexts.

The actualization of affordances can often be accomplished in numerous, equifinal ways. For insta... more The actualization of affordances can often be accomplished in numerous, equifinal ways. For instance, an individual could discard an item in a rubbish bin by walking over and dropping it, or by throwing it from a distance. The aim of the current study was to investigate the behavioral dynamics associated with such metastability using a ball-to-bin transportation task. Using time-interval between sequential ball-presentation as a control parameter, participants transported balls from a pickup location to a drop-off bin 9m away. A high degree of variability in task-actualization was expected and found, and the Cusp Catatrophe model was used to understand how this behavioral variability emerged as a function of hard (time interval) and soft (e.g. motivation) task dynamic constraints. Simulations demonstrated that this two parameter state manifold could capture the wide range of participant behaviors, and explain how these behaviors naturally emerge in an under-constrained task context.

Journal of Biomechanics, 2011

Continuous relative phase measures have been used to quantify the coordination between different ... more Continuous relative phase measures have been used to quantify the coordination between different body segments in several activities. Our aim in this study was to investigate how the methods traditionally used to compute the continuous phase of human rhythmic movement are affected by modulations of frequency. We compared the continuous phase computed method with the traditional method derived from the position-velocity phase plane and with the Hilbert Transform. The methods were tested using sinusoidal signals with a modulation of frequency between or within cycles. Our results showed that the continuous phase computed with the first method results in oscillations in the phase time-series not expected for a sinusoidal signal and that the continuous phase is overestimated with the Hilbert Transform. We proposed a new method that produces a correct estimation of continuous phase by using half-cycle estimations of frequency to normalize the phase planes prior to calculating phase angles. The findings of the current study have important implications for computing continuous relative phase when investigating human movement coordination.

There is contention in perceptual-motor research concerning the degree to which observing biologi... more There is contention in perceptual-motor research concerning the degree to which observing biological and non-biological movements have equivalent effects on movement production. This issue results from the proposal that action observation and production share neural resources (i.e., mirror neurons) particularly sensitive to actions performed by other 'agents' (i.e., beings with goals/intentions). In support of this claim, several discrete and rhythmic action-observation studies found that action production is only affected when participants believed that observed actions were produced by an agent. Here we present data from two experiments investigating whether similar agency manipulations also affect spontaneous movement synchrony. Collectively, the results suggest that belief in the 'agency' of an observed movement does not affect the emergence and stability of rhythmic movement synchrony. These results question whether the actions of other agents are truly privileged across all scales of coordinated activity, particularly with respect to the lawful dynamics underlying movement synchrony.

Frontiers in human neuroscience, 2012

Traditional theories of cognitive science have typically accounted for the organization of human ... more Traditional theories of cognitive science have typically accounted for the organization of human behavior by detailing requisite computational/representational functions and identifying neurological mechanisms that might perform these functions. Put simply, such approaches hold that neural activity causes behavior. This same general framework has been extended to accounts of human social behavior via concepts such as "common-coding" and "co-representation" and much recent neurological research has been devoted to brain structures that might execute these social-cognitive functions. Although these neural processes are unquestionably involved in the organization and control of human social interactions, there is good reason to question whether they should be accorded explanatory primacy. Alternatively, we propose that a full appreciation of the role of neural processes in social interactions requires appropriately situating them in their context of embodied-embedde...

Experimental Brain Research, 2011

The current project evaluated the relationship between the stability of intrapersonal coordinatio... more The current project evaluated the relationship between the stability of intrapersonal coordination and the emergence of spontaneous interpersonal coordination. Participants were organized into pairs, and each participant was instructed to produce either an inphase or antiphase pattern of intrapersonal bimanual coordination using two hand-held pendulums, while simultaneously performing an interpersonal puzzle task. At issue was whether the emergence and stability of spontaneous interpersonal rhythmic coordination is inXuenced by ("Experiment 1") the stability of the intrapersonal coordination patterns produced by coactors and ("Experiment 2") the congruency of the intrapersonal coordination patterns produced by co-actors. The stability of intrapersonal movement coordination did not aVect the emergence of spontaneous interpersonal coordination. The degree of interpersonal coordination observed was similar when both participants in a pair produced either inphase or antiphase patterns of intrapersonal bimanual coordination. Moreover, the congruency of the intrapersonal coordination patterns only slightly aVected the emergence of interpersonal coordination, with only marginally lower inphase interpersonal entrainment when participants produced incongruent patterns of intrapersonal coordination (e.g., inphase-antiphase). Interestingly, movement observation and the emergence of interpersonal coordination did not aVect the stability of intrapersonal bimanual coordination. The results suggest that interlimb rhythmic bimanual coordination reXects a single intrapersonal perceptual-motor synergy and that these bimanual synergies (not individual limbs) are what become spontaneously entrained interpersonally.

Human movement science, Jan 7, 2015

Past research has revealed that an individual's rhythmic limb movements become spontaneously ... more Past research has revealed that an individual's rhythmic limb movements become spontaneously entrained to an environmental rhythm if visual information about the rhythm is available and its frequency is near that of the individual's movements. Research has also demonstrated that if the eyes track an environmental stimulus, the spontaneous entrainment to the rhythm is strengthened. One hypothesis explaining this enhancement of spontaneous entrainment is that the limb movements and eye movements are linked through a neuromuscular coupling or synergy. Another is that eye-tracking facilitates the pick up of important coordinating information. Experiment 1 investigated the first hypothesis by evaluating whether any rhythmic movement of the eyes would facilitate spontaneous entrainment. Experiments 2 and 3 (respectively) explored whether eye-tracking strengthens spontaneous entrainment by allowing the pickup of trajectory direction change information or allowing an increase in the...

Journal of experimental psychology. Human perception and performance, 2014

Every day, we visually coordinate our movements with environmental rhythms. Despite its ubiquity,... more Every day, we visually coordinate our movements with environmental rhythms. Despite its ubiquity, it largely remains unclear why certain visual rhythms or stimuli facilitate such visuomotor coordination. The goal of the current study was to investigate whether the velocity profile of a rhythmic stimulus modulated the emergence and stability of this coordination. We examined both intended (Experiment 1) and unintended or spontaneous coordination (Experiment 2) between the rhythmic limb movements of participants and stimuli exhibiting different velocity profiles. Specifically, the stimuli oscillated with either a sinusoidal (harmonic), nonlinear Rayleigh, or nonlinear Van der Pol velocity profile, all of which are typical of human or biological rhythmic movement. The results demonstrated that the dynamics of both intended and unintended visuomotor coordination were modulated by the stimulus velocity profile, and that the Rayleigh velocity profile facilitated the coordination, suggesti...

Journal of Experimental Psychology: Human Perception and Performance, 2015

Despite the desire of athletes to separate themselves from their competitors, to be faster or bet... more Despite the desire of athletes to separate themselves from their competitors, to be faster or better, their performance is often influenced by those they are competing with. Here we show that the unintentional or spontaneous interpersonal synchronization of athletes' movements may partially account for such performance modifications. We examined the 100-m final of Usain Bolt in the 12th IAAF World Championship in Athletics (Berlin, 2009) in which he broke the world record, and demonstrate that Usain Bolt and Tyson Gay who ran side-by-side throughout the race spontaneously and intermittently synchronized their steps. This finding demonstrates that even the most optimized individual motor skills can be modulated by the simple presence of another individual via interpersonal coordination processes. It extends previous research by showing that the hard constraints of individual motor performance do not overwhelm the occurrence of spontaneous interpersonal synchronization and open promising new research directions for better understanding and improving athletic performance.

Human Movement Science, 2012

Rhythmic limb movements have been shown to spontaneously coordinate with rhythmic environmental s... more Rhythmic limb movements have been shown to spontaneously coordinate with rhythmic environmental stimuli. Previous research has demonstrated how such entrainment depends on the difference between the movement periods of the limb and the stimulus, and on the degree to which the actor visually tracks the stimulus. Here we present an experiment that investigated how stimulus amplitude influences unintended visuomotor entrainment. Participants performed rhythmic forearm movements while visually tracking an oscillating stimulus. The amplitude and period of stimulus motion were manipulated. Larger stimulus amplitudes resulted in stronger entrainment irrespective of how participants visually tracked the movements of the stimulus. Visual tracking, however, did result in increased entrainment for large, but not small, stimulus amplitudes. Collectively, the results indicate that the movement amplitude of environmental stimuli plays a significant role in the emergence of unintended visuomotor entrainment.

Frontiers in Psychology, 2015

Understanding everyday behavior relies heavily upon understanding our ability to improvise, how w... more Understanding everyday behavior relies heavily upon understanding our ability to improvise, how we are able to continuously anticipate and adapt in order to coordinate with our environment and others. Here we consider the ability of musicians to improvise, where they must spontaneously coordinate their actions with co-performers in order to produce novel musical expressions. Investigations of this behavior have traditionally focused on describing the organization of cognitive structures. The focus, here, however, is on the ability of the time-evolving patterns of inter-musician movement coordination as revealed by the mathematical tools of complex dynamical systems to provide a new understanding of what potentiates the novelty of spontaneous musical action. We demonstrate this approach through the application of cross wavelet spectral analysis, which isolates the strength and patterning of the behavioral coordination that occurs between improvising musicians across a range of nested time-scales. Revealing the sophistication of the previously unexplored dynamics of movement coordination between improvising musicians is an important step toward understanding how creative musical expressions emerge from the spontaneous coordination of multiple musical bodies.

Nonlinear dynamics, psychology, and life sciences, 2015

A display that contains hierarchically nested levels of order requires the perceiver to selective... more A display that contains hierarchically nested levels of order requires the perceiver to selectively attend to one of the levels. We investigate the degree to which such selective attention is sustained by a soft-assembled emergent coordinative process, one that does not require designated executive control. In the case of emergent soft-assembly, performance from one trial to the next should show characteristic interdependence, visible in the fractal structure of reaction time. To test this hypothesis, we asked participants across three experiments to decide whether two displays matched in a certain way (e.g., in a local element). In order to gauge this coordinative process, task constraints were experimentally manipulated (e.g., familiarity, predictability, and task instruction). Obtained reaction-time data were subjected to a spectral analysis to measure the degree of interdependence among trials. As predicted, results show correlated structure across trials, significantly differen...

Journal of experimental psychology. Human perception and performance, Jan 9, 2015

Understanding stable patterns of interpersonal movement coordination is essential to understandin... more Understanding stable patterns of interpersonal movement coordination is essential to understanding successful social interaction and activity (i.e., joint action). Previous research investigating such coordination has primarily focused on the synchronization of simple rhythmic movements (e.g., finger/forearm oscillations or pendulum swinging). Very few studies, however, have explored the stable patterns of coordination that emerge during task-directed complementary coordination tasks. Thus, the aim of the current study was to investigate and model the behavioral dynamics of a complementary collision-avoidance task. Participant pairs performed a repetitive targeting task in which they moved computer stimuli back and forth between sets of target locations without colliding into each other. The results revealed that pairs quickly converged onto a stable, asymmetric pattern of movement coordination that reflected differential control across participants, with 1 participant adopting a mo...

Frontiers in Human Neuroscience, 2014

For many everyday sensorimotor tasks, trained dancers have been found to exhibit distinct and som... more For many everyday sensorimotor tasks, trained dancers have been found to exhibit distinct and sometimes superior (more stable or robust) patterns of behavior compared to non-dancers. Past research has demonstrated that experts in fields requiring specialized physical training and behavioral control exhibit superior interpersonal coordination capabilities for expertise-related tasks. To date, however, no published studies have compared dancers' abilities to coordinate their movements with the movements of another individual-i.e., during a so-called visual-motor interpersonal coordination task. The current study was designed to investigate whether trained dancers would be better able to coordinate with a partner performing short sequences of dance-like movements than non-dancers. Movement time series were recorded for individual dancers and non-dancers asked to synchronize with a confederate during three different movement sequences characterized by distinct dance styles (i.e., dance team routine, contemporary ballet, mixed style) without hearing any auditory signals or music. A diverse range of linear and non-linear analyses (i.e., cross-correlation, cross-recurrence quantification analysis, and cross-wavelet analysis) provided converging measures of coordination across multiple time scales. While overall levels of interpersonal coordination were influenced by differences in movement sequence for both groups, dancers consistently displayed higher levels of coordination with the confederate at both short and long time scales. These findings demonstrate that the visual-motor coordination capabilities of trained dancers allow them to better synchronize with other individuals performing dance-like movements than non-dancers. Further investigation of similar tasks may help to increase the understanding of visual-motor entrainment in general, as well as provide insight into the effects of focused training on visual-motor and interpersonal coordination.

Frontiers in Physiology

A new method for assessing group synchrony is introduced as being potentially useful for objectiv... more A new method for assessing group synchrony is introduced as being potentially useful for objectively determining degree of group cohesiveness or entitativity. The cluster-phase method of Frank and Richardson (2010) was used to analyze movement data from the rocking chair movements of six-member groups who rocked their chairs while seated in a circle facing the center. In some trials group members had no information about others' movements (their eyes were shut) or they had their eyes open and gazed at a marker in the center of the group. As predicted, the group level synchrony measure was able to distinguish between situations where synchrony would have been possible and situations where it would be impossible. Moreover, other aspects of the analysis illustrated how the cluster phase measures can be used to determine the type of patterning of group synchrony, and, when integrated with multi-level modeling, can be used to examine individual-level differences in synchrony and dyad...

PLoS ONE, 2014

The mere presence of a co-actor can influence an individual's response behavior. For instance, a ... more The mere presence of a co-actor can influence an individual's response behavior. For instance, a social Simon effect has been observed when two individuals perform a Go/No-Go response to one of two stimuli in the presence of each other, but not when they perform the same task alone. Such effects are argued to provide evidence that individuals co-represent the task goals and the to-be-performed actions of a co-actor. Motivated by the complex-systems approach, the present study was designed to investigate an alternative hypothesisthat such joint-action effects are due to dynamical (timeevolving) entrainment processes that perturb and couple the behavior of socially situated actors. To investigate this possibility, participants performed a standard Go/No-Go Simon task in joint and individual conditions. The dynamic structure of recorded response times (RTs) was examined using fractal statistics and instantaneous cross-correlation. Consistent with our hypothesis that participants responding in a shared space would become behaviorally coupled, the analyses revealed that RTs in the joint condition displayed decreased fractal structure (indicative of an interpersonal coupling perturbing and constraining participant behavior) compared to the individual condition, and were more correlated across a range of time-scales compared to the RTs of pseudo-pair controls. Collectively, the findings imply that self-organizing dynamic processes might underlie social stimulus-response compatibility effects and shape joint cognitive processes in general.

Journal of Motor Behavior, 2009

Motivated by previous research suggesting that informational and mechanical interlimb coupling ca... more Motivated by previous research suggesting that informational and mechanical interlimb coupling can stabilize rhythmic movement patterns, the authors show that stable 4-legged patterns between 2 individuals, either walking or running, can emerge unintentionally from simple forms of coupling. Specifically, they show that the leg movements of pairs of naive individuals become spontaneously phase locked when visually or mechanically coupled via a foam appendage. Analysis of each of the phase locked trials revealed distinct preferences for particular 4-legged patterns, with interpersonal in-and anti-phase coordination patterns (equitable with quadruped pace and trot, respectively) observed almost exclusively. Preference for either pattern depended on the strength of coupling. The authors discuss these findings in light of previous claims that the patterns of human and animal locomotion-as well as coordinated movements in general-can emerge from lawful coupling relations that exist between the subcomponents of perceptual-motor systems.

Human Movement Science, 2007

The current study investigated the interpersonal coordination that occurred between two people wh... more The current study investigated the interpersonal coordination that occurred between two people when sitting side-by-side in rocking chairs. In two experiments participant pairs rocked in chairs that had the same or different natural periods. By instructing pairs to coordinate their movements inphase or antiphase, Experiment 1 investigated whether the stable patterns of intentional interpersonal coordination were consistent with the dynamics of within person interlimb coordination. By instructing the participants to rock at their own preferred tempo, Experiment 2 investigated whether the rocking chair movements of visually coupled individuals would become unintentionally coordinated. The degree to which the participants fixated on the movements of their co-actor was also manipulated to examine whether visual focus modulates the strength of interpersonal coordination. As expected, the patterns of coordination observed in both experiments demonstrated that the intentional and unintentional interpersonal coordination of rocking chair movements is constrained by the self-organizing dynamics of a coupled oscillator system. The results of the visual focus manipulations indicate that the stability of a visual interpersonal coupling is mediated by attention and the degree to which an individual is able to detect information about a co-actor's movements.

Frontiers in Integrative Neuroscience, 2013

Individuals with autism spectrum disorders (ASDs) have significant visuomotor processing deficits... more Individuals with autism spectrum disorders (ASDs) have significant visuomotor processing deficits, atypical motoric behavior, and often substantial problems connecting socially. We suggest that the perceptual, attentional, and adaptive timing deficiencies associated with autism might directly impact the ability to become a socially connected unit with others. Using a rocking chair paradigm previously employed with typical adults, we demonstrate that typically-developing (TD) children exhibit spontaneous social rocking with their caregivers. In contrast, children diagnosed with ASD do not demonstrate a tendency to rock in a symmetrical state with their parents. We argue that the movement of our bodies is one of the fundamental ways by which we connect with our environment and, especially, ground ourselves in social environments. Deficiencies in perceiving and responding to the rhythms of the world may have serious consequences for the ability to become adequately embedded in a social context.

Frontiers in Psychology, 2015

Understanding everyday behavior relies heavily upon understanding our ability to improvise, how w... more Understanding everyday behavior relies heavily upon understanding our ability to improvise, how we are able to continuously anticipate and adapt in order to coordinate with our environment and others. Here we consider the ability of musicians to improvise, where they must spontaneously coordinate their actions with co-performers in order to produce novel musical expressions. Investigations of this behavior have traditionally focused on describing the organization of cognitive structures. The focus, here, however, is on the ability of the time-evolving patterns of inter-musician movement coordination as revealed by the mathematical tools of complex dynamical systems to provide a new understanding of what potentiates the novelty of spontaneous musical action. We demonstrate this approach through the application of cross wavelet spectral analysis, which isolates the strength and patterning of the behavioral coordination that occurs between improvising musicians across a range of nested time-scales. Revealing the sophistication of the previously unexplored dynamics of movement coordination between improvising musicians is an important step toward understanding how creative musical expressions emerge from the spontaneous coordination of multiple musical bodies.

Biological systems are capable of acting in a shared environment to produce emergent, self-organi... more Biological systems are capable of acting in a shared environment to produce emergent, self-organized behavior that is the result of the constraints imposed by local interactions– such as bird flocking or ant swarming behavior. These examples present minimal demands for a shared-intention between co-actors, whereas other instances necessitate the formation of a shared goal. In these goal-directed tasks, how much of the observed complexity can be explained by the constraints imposed by both the environment and adherence to the shared task goal? This paper begins to investigate this question by presenting results from a two-person cooperative " shepherding " task first developed in Nalepka et al. (2017) but with fewer constraints. Results provide further evidence that the emergent behavior is the result of the constraints imposed by the task. The included task-dynamic model suggests a general model that can be used to understand multiagent herding behavior in a variety of contexts.

The actualization of affordances can often be accomplished in numerous, equifinal ways. For insta... more The actualization of affordances can often be accomplished in numerous, equifinal ways. For instance, an individual could discard an item in a rubbish bin by walking over and dropping it, or by throwing it from a distance. The aim of the current study was to investigate the behavioral dynamics associated with such metastability using a ball-to-bin transportation task. Using time-interval between sequential ball-presentation as a control parameter, participants transported balls from a pickup location to a drop-off bin 9m away. A high degree of variability in task-actualization was expected and found, and the Cusp Catatrophe model was used to understand how this behavioral variability emerged as a function of hard (time interval) and soft (e.g. motivation) task dynamic constraints. Simulations demonstrated that this two parameter state manifold could capture the wide range of participant behaviors, and explain how these behaviors naturally emerge in an under-constrained task context.

Journal of Biomechanics, 2011

Continuous relative phase measures have been used to quantify the coordination between different ... more Continuous relative phase measures have been used to quantify the coordination between different body segments in several activities. Our aim in this study was to investigate how the methods traditionally used to compute the continuous phase of human rhythmic movement are affected by modulations of frequency. We compared the continuous phase computed method with the traditional method derived from the position-velocity phase plane and with the Hilbert Transform. The methods were tested using sinusoidal signals with a modulation of frequency between or within cycles. Our results showed that the continuous phase computed with the first method results in oscillations in the phase time-series not expected for a sinusoidal signal and that the continuous phase is overestimated with the Hilbert Transform. We proposed a new method that produces a correct estimation of continuous phase by using half-cycle estimations of frequency to normalize the phase planes prior to calculating phase angles. The findings of the current study have important implications for computing continuous relative phase when investigating human movement coordination.

There is contention in perceptual-motor research concerning the degree to which observing biologi... more There is contention in perceptual-motor research concerning the degree to which observing biological and non-biological movements have equivalent effects on movement production. This issue results from the proposal that action observation and production share neural resources (i.e., mirror neurons) particularly sensitive to actions performed by other 'agents' (i.e., beings with goals/intentions). In support of this claim, several discrete and rhythmic action-observation studies found that action production is only affected when participants believed that observed actions were produced by an agent. Here we present data from two experiments investigating whether similar agency manipulations also affect spontaneous movement synchrony. Collectively, the results suggest that belief in the 'agency' of an observed movement does not affect the emergence and stability of rhythmic movement synchrony. These results question whether the actions of other agents are truly privileged across all scales of coordinated activity, particularly with respect to the lawful dynamics underlying movement synchrony.

Frontiers in human neuroscience, 2012

Traditional theories of cognitive science have typically accounted for the organization of human ... more Traditional theories of cognitive science have typically accounted for the organization of human behavior by detailing requisite computational/representational functions and identifying neurological mechanisms that might perform these functions. Put simply, such approaches hold that neural activity causes behavior. This same general framework has been extended to accounts of human social behavior via concepts such as "common-coding" and "co-representation" and much recent neurological research has been devoted to brain structures that might execute these social-cognitive functions. Although these neural processes are unquestionably involved in the organization and control of human social interactions, there is good reason to question whether they should be accorded explanatory primacy. Alternatively, we propose that a full appreciation of the role of neural processes in social interactions requires appropriately situating them in their context of embodied-embedde...

Experimental Brain Research, 2011

The current project evaluated the relationship between the stability of intrapersonal coordinatio... more The current project evaluated the relationship between the stability of intrapersonal coordination and the emergence of spontaneous interpersonal coordination. Participants were organized into pairs, and each participant was instructed to produce either an inphase or antiphase pattern of intrapersonal bimanual coordination using two hand-held pendulums, while simultaneously performing an interpersonal puzzle task. At issue was whether the emergence and stability of spontaneous interpersonal rhythmic coordination is inXuenced by ("Experiment 1") the stability of the intrapersonal coordination patterns produced by coactors and ("Experiment 2") the congruency of the intrapersonal coordination patterns produced by co-actors. The stability of intrapersonal movement coordination did not aVect the emergence of spontaneous interpersonal coordination. The degree of interpersonal coordination observed was similar when both participants in a pair produced either inphase or antiphase patterns of intrapersonal bimanual coordination. Moreover, the congruency of the intrapersonal coordination patterns only slightly aVected the emergence of interpersonal coordination, with only marginally lower inphase interpersonal entrainment when participants produced incongruent patterns of intrapersonal coordination (e.g., inphase-antiphase). Interestingly, movement observation and the emergence of interpersonal coordination did not aVect the stability of intrapersonal bimanual coordination. The results suggest that interlimb rhythmic bimanual coordination reXects a single intrapersonal perceptual-motor synergy and that these bimanual synergies (not individual limbs) are what become spontaneously entrained interpersonally.

Human movement science, Jan 7, 2015

Past research has revealed that an individual's rhythmic limb movements become spontaneously ... more Past research has revealed that an individual's rhythmic limb movements become spontaneously entrained to an environmental rhythm if visual information about the rhythm is available and its frequency is near that of the individual's movements. Research has also demonstrated that if the eyes track an environmental stimulus, the spontaneous entrainment to the rhythm is strengthened. One hypothesis explaining this enhancement of spontaneous entrainment is that the limb movements and eye movements are linked through a neuromuscular coupling or synergy. Another is that eye-tracking facilitates the pick up of important coordinating information. Experiment 1 investigated the first hypothesis by evaluating whether any rhythmic movement of the eyes would facilitate spontaneous entrainment. Experiments 2 and 3 (respectively) explored whether eye-tracking strengthens spontaneous entrainment by allowing the pickup of trajectory direction change information or allowing an increase in the...

Journal of experimental psychology. Human perception and performance, 2014

Every day, we visually coordinate our movements with environmental rhythms. Despite its ubiquity,... more Every day, we visually coordinate our movements with environmental rhythms. Despite its ubiquity, it largely remains unclear why certain visual rhythms or stimuli facilitate such visuomotor coordination. The goal of the current study was to investigate whether the velocity profile of a rhythmic stimulus modulated the emergence and stability of this coordination. We examined both intended (Experiment 1) and unintended or spontaneous coordination (Experiment 2) between the rhythmic limb movements of participants and stimuli exhibiting different velocity profiles. Specifically, the stimuli oscillated with either a sinusoidal (harmonic), nonlinear Rayleigh, or nonlinear Van der Pol velocity profile, all of which are typical of human or biological rhythmic movement. The results demonstrated that the dynamics of both intended and unintended visuomotor coordination were modulated by the stimulus velocity profile, and that the Rayleigh velocity profile facilitated the coordination, suggesti...

Journal of Experimental Psychology: Human Perception and Performance, 2015

Despite the desire of athletes to separate themselves from their competitors, to be faster or bet... more Despite the desire of athletes to separate themselves from their competitors, to be faster or better, their performance is often influenced by those they are competing with. Here we show that the unintentional or spontaneous interpersonal synchronization of athletes' movements may partially account for such performance modifications. We examined the 100-m final of Usain Bolt in the 12th IAAF World Championship in Athletics (Berlin, 2009) in which he broke the world record, and demonstrate that Usain Bolt and Tyson Gay who ran side-by-side throughout the race spontaneously and intermittently synchronized their steps. This finding demonstrates that even the most optimized individual motor skills can be modulated by the simple presence of another individual via interpersonal coordination processes. It extends previous research by showing that the hard constraints of individual motor performance do not overwhelm the occurrence of spontaneous interpersonal synchronization and open promising new research directions for better understanding and improving athletic performance.

Human Movement Science, 2012

Rhythmic limb movements have been shown to spontaneously coordinate with rhythmic environmental s... more Rhythmic limb movements have been shown to spontaneously coordinate with rhythmic environmental stimuli. Previous research has demonstrated how such entrainment depends on the difference between the movement periods of the limb and the stimulus, and on the degree to which the actor visually tracks the stimulus. Here we present an experiment that investigated how stimulus amplitude influences unintended visuomotor entrainment. Participants performed rhythmic forearm movements while visually tracking an oscillating stimulus. The amplitude and period of stimulus motion were manipulated. Larger stimulus amplitudes resulted in stronger entrainment irrespective of how participants visually tracked the movements of the stimulus. Visual tracking, however, did result in increased entrainment for large, but not small, stimulus amplitudes. Collectively, the results indicate that the movement amplitude of environmental stimuli plays a significant role in the emergence of unintended visuomotor entrainment.

Frontiers in Psychology, 2015

Understanding everyday behavior relies heavily upon understanding our ability to improvise, how w... more Understanding everyday behavior relies heavily upon understanding our ability to improvise, how we are able to continuously anticipate and adapt in order to coordinate with our environment and others. Here we consider the ability of musicians to improvise, where they must spontaneously coordinate their actions with co-performers in order to produce novel musical expressions. Investigations of this behavior have traditionally focused on describing the organization of cognitive structures. The focus, here, however, is on the ability of the time-evolving patterns of inter-musician movement coordination as revealed by the mathematical tools of complex dynamical systems to provide a new understanding of what potentiates the novelty of spontaneous musical action. We demonstrate this approach through the application of cross wavelet spectral analysis, which isolates the strength and patterning of the behavioral coordination that occurs between improvising musicians across a range of nested time-scales. Revealing the sophistication of the previously unexplored dynamics of movement coordination between improvising musicians is an important step toward understanding how creative musical expressions emerge from the spontaneous coordination of multiple musical bodies.

Nonlinear dynamics, psychology, and life sciences, 2015

A display that contains hierarchically nested levels of order requires the perceiver to selective... more A display that contains hierarchically nested levels of order requires the perceiver to selectively attend to one of the levels. We investigate the degree to which such selective attention is sustained by a soft-assembled emergent coordinative process, one that does not require designated executive control. In the case of emergent soft-assembly, performance from one trial to the next should show characteristic interdependence, visible in the fractal structure of reaction time. To test this hypothesis, we asked participants across three experiments to decide whether two displays matched in a certain way (e.g., in a local element). In order to gauge this coordinative process, task constraints were experimentally manipulated (e.g., familiarity, predictability, and task instruction). Obtained reaction-time data were subjected to a spectral analysis to measure the degree of interdependence among trials. As predicted, results show correlated structure across trials, significantly differen...

Journal of experimental psychology. Human perception and performance, Jan 9, 2015

Understanding stable patterns of interpersonal movement coordination is essential to understandin... more Understanding stable patterns of interpersonal movement coordination is essential to understanding successful social interaction and activity (i.e., joint action). Previous research investigating such coordination has primarily focused on the synchronization of simple rhythmic movements (e.g., finger/forearm oscillations or pendulum swinging). Very few studies, however, have explored the stable patterns of coordination that emerge during task-directed complementary coordination tasks. Thus, the aim of the current study was to investigate and model the behavioral dynamics of a complementary collision-avoidance task. Participant pairs performed a repetitive targeting task in which they moved computer stimuli back and forth between sets of target locations without colliding into each other. The results revealed that pairs quickly converged onto a stable, asymmetric pattern of movement coordination that reflected differential control across participants, with 1 participant adopting a mo...

Frontiers in Human Neuroscience, 2014

For many everyday sensorimotor tasks, trained dancers have been found to exhibit distinct and som... more For many everyday sensorimotor tasks, trained dancers have been found to exhibit distinct and sometimes superior (more stable or robust) patterns of behavior compared to non-dancers. Past research has demonstrated that experts in fields requiring specialized physical training and behavioral control exhibit superior interpersonal coordination capabilities for expertise-related tasks. To date, however, no published studies have compared dancers' abilities to coordinate their movements with the movements of another individual-i.e., during a so-called visual-motor interpersonal coordination task. The current study was designed to investigate whether trained dancers would be better able to coordinate with a partner performing short sequences of dance-like movements than non-dancers. Movement time series were recorded for individual dancers and non-dancers asked to synchronize with a confederate during three different movement sequences characterized by distinct dance styles (i.e., dance team routine, contemporary ballet, mixed style) without hearing any auditory signals or music. A diverse range of linear and non-linear analyses (i.e., cross-correlation, cross-recurrence quantification analysis, and cross-wavelet analysis) provided converging measures of coordination across multiple time scales. While overall levels of interpersonal coordination were influenced by differences in movement sequence for both groups, dancers consistently displayed higher levels of coordination with the confederate at both short and long time scales. These findings demonstrate that the visual-motor coordination capabilities of trained dancers allow them to better synchronize with other individuals performing dance-like movements than non-dancers. Further investigation of similar tasks may help to increase the understanding of visual-motor entrainment in general, as well as provide insight into the effects of focused training on visual-motor and interpersonal coordination.

Frontiers in Physiology

A new method for assessing group synchrony is introduced as being potentially useful for objectiv... more A new method for assessing group synchrony is introduced as being potentially useful for objectively determining degree of group cohesiveness or entitativity. The cluster-phase method of Frank and Richardson (2010) was used to analyze movement data from the rocking chair movements of six-member groups who rocked their chairs while seated in a circle facing the center. In some trials group members had no information about others' movements (their eyes were shut) or they had their eyes open and gazed at a marker in the center of the group. As predicted, the group level synchrony measure was able to distinguish between situations where synchrony would have been possible and situations where it would be impossible. Moreover, other aspects of the analysis illustrated how the cluster phase measures can be used to determine the type of patterning of group synchrony, and, when integrated with multi-level modeling, can be used to examine individual-level differences in synchrony and dyad...

PLoS ONE, 2014

The mere presence of a co-actor can influence an individual's response behavior. For instance, a ... more The mere presence of a co-actor can influence an individual's response behavior. For instance, a social Simon effect has been observed when two individuals perform a Go/No-Go response to one of two stimuli in the presence of each other, but not when they perform the same task alone. Such effects are argued to provide evidence that individuals co-represent the task goals and the to-be-performed actions of a co-actor. Motivated by the complex-systems approach, the present study was designed to investigate an alternative hypothesisthat such joint-action effects are due to dynamical (timeevolving) entrainment processes that perturb and couple the behavior of socially situated actors. To investigate this possibility, participants performed a standard Go/No-Go Simon task in joint and individual conditions. The dynamic structure of recorded response times (RTs) was examined using fractal statistics and instantaneous cross-correlation. Consistent with our hypothesis that participants responding in a shared space would become behaviorally coupled, the analyses revealed that RTs in the joint condition displayed decreased fractal structure (indicative of an interpersonal coupling perturbing and constraining participant behavior) compared to the individual condition, and were more correlated across a range of time-scales compared to the RTs of pseudo-pair controls. Collectively, the findings imply that self-organizing dynamic processes might underlie social stimulus-response compatibility effects and shape joint cognitive processes in general.

Journal of Motor Behavior, 2009

Motivated by previous research suggesting that informational and mechanical interlimb coupling ca... more Motivated by previous research suggesting that informational and mechanical interlimb coupling can stabilize rhythmic movement patterns, the authors show that stable 4-legged patterns between 2 individuals, either walking or running, can emerge unintentionally from simple forms of coupling. Specifically, they show that the leg movements of pairs of naive individuals become spontaneously phase locked when visually or mechanically coupled via a foam appendage. Analysis of each of the phase locked trials revealed distinct preferences for particular 4-legged patterns, with interpersonal in-and anti-phase coordination patterns (equitable with quadruped pace and trot, respectively) observed almost exclusively. Preference for either pattern depended on the strength of coupling. The authors discuss these findings in light of previous claims that the patterns of human and animal locomotion-as well as coordinated movements in general-can emerge from lawful coupling relations that exist between the subcomponents of perceptual-motor systems.

Human Movement Science, 2007

The current study investigated the interpersonal coordination that occurred between two people wh... more The current study investigated the interpersonal coordination that occurred between two people when sitting side-by-side in rocking chairs. In two experiments participant pairs rocked in chairs that had the same or different natural periods. By instructing pairs to coordinate their movements inphase or antiphase, Experiment 1 investigated whether the stable patterns of intentional interpersonal coordination were consistent with the dynamics of within person interlimb coordination. By instructing the participants to rock at their own preferred tempo, Experiment 2 investigated whether the rocking chair movements of visually coupled individuals would become unintentionally coordinated. The degree to which the participants fixated on the movements of their co-actor was also manipulated to examine whether visual focus modulates the strength of interpersonal coordination. As expected, the patterns of coordination observed in both experiments demonstrated that the intentional and unintentional interpersonal coordination of rocking chair movements is constrained by the self-organizing dynamics of a coupled oscillator system. The results of the visual focus manipulations indicate that the stability of a visual interpersonal coupling is mediated by attention and the degree to which an individual is able to detect information about a co-actor's movements.

Frontiers in Integrative Neuroscience, 2013

Individuals with autism spectrum disorders (ASDs) have significant visuomotor processing deficits... more Individuals with autism spectrum disorders (ASDs) have significant visuomotor processing deficits, atypical motoric behavior, and often substantial problems connecting socially. We suggest that the perceptual, attentional, and adaptive timing deficiencies associated with autism might directly impact the ability to become a socially connected unit with others. Using a rocking chair paradigm previously employed with typical adults, we demonstrate that typically-developing (TD) children exhibit spontaneous social rocking with their caregivers. In contrast, children diagnosed with ASD do not demonstrate a tendency to rock in a symmetrical state with their parents. We argue that the movement of our bodies is one of the fundamental ways by which we connect with our environment and, especially, ground ourselves in social environments. Deficiencies in perceiving and responding to the rhythms of the world may have serious consequences for the ability to become adequately embedded in a social context.