Tognoli, Emmanuelle

A fundamental question in Complexity Science is how numerous dynamic processes
coordinate with each other on multiple levels of description to form a complex
whole - a multiscale coordinative structure (e.g. a community of interacting people,
organs, cells, molecules etc.). This dissertation includes a series of empirical, theoretical
and methodological studies of rhythmic coordination between multiple agents
to uncover dynamic principles underlying multiscale coordinative structures. First,
a new experimental paradigm was developed for studying coordination at multiple
levels of description in intermediate-sized (N = 8) ensembles of humans. Based
on this paradigm, coordination dynamics in 15 ensembles was examined experimentally,
where the diversity of subjects movement frequency was manipulated to induce
di erent grouping behavior. Phase coordination between subjects was found to be
metastable with inphase and antiphase tendencies. Higher frequency diversity led
to segregation between frequency groups, reduced intragroup coordination, and dispersion
of dyadic phase relations (i.e. relations at di erent levels of description).
Subsequently, a model was developed, successfully capturing these observations. The
model reconciles the Kuramoto and the extended Haken-Kelso-Bunz model (for large- and small-scale coordination respectively) by adding the second-order coupling from
the latter to the former. The second order coupling is indispensable in capturing
experimental observations and connects behavioral complexity (i.e. multistability) of
coordinative structures across scales. Both the experimental and theoretical studies
revealed multiagent metastable coordination as a powerful mechanism for generating
complex spatiotemporal patterns. Coexistence of multiple phase relations gives rise
to many topologically distinct metastable patterns with di erent degrees of complexity.
Finally, a new data-analytic tool was developed to quantify complex metastable
patterns based on their topological features. The recurrence of topological features
revealed important structures and transitions in high-dimensional dynamic patterns
that eluded its non-topological counterparts. Taken together, the work has paved the
way for a deeper understanding of multiscale coordinative structures.

Emotion and coordinated movement complimentarily depicts our social experiences.
How is motion colored? This study investigates variations in emotional responses during social
coordination. Subjects were instructed to coordinate their finger movement with a Virtual Partner
(VP), whose homologous movement was displayed as a video on the computer screen. The
partner was driven by the Haken-Kelso-Bunz equations, an empirically validated model that
captures behavioral and social coordination. It has been shown that people perceive VP as an
intentional human agent. In each of 80 trials, subjects coordinated for 8 sec inphase or antiphase
with VP, and then rated the partner’s intention (cooperation -VP intend same coordination
pattern as human-, or competition) and subjective response to a Turing test of partners’
humanness. VP cooperated for half of the time, and could change its intention in the middle of a
trial. Skin potential response (SPR) quantified the intensity of emotional responses. After
validating the SPR measurements, we compared emotional responses by coordination pattern,
cooperative~competitiveness, and humanness attribution. Subjects experienced higher emotional
responses when they believed that their partner was human. This was observed both during
coordination (ANOVA, p=0.020), and during rating (p=0.012). Furthermore during the rating
period, higher emotional responses were found for cooperative behavior (p=0.012), modulated
by VP’s change of intention and coordination pattern. This study suggests that emotional
responses are strongly influenced by features of the partner’s behavior associated with
humanness, cooperation and change of intention. Implications for mental health (e.g. autism) and
design of socially cooperative machines will be discussed.

How one behaves after interacting with a friend may not be the same as before
the interaction began What factors a ect the formation of social interactions
between people and, once formed, how do social interactions leave lasting changes on
individual behavior? In this dissertation, a thorough review and conceptual synthesis
is provided Major features of coordination dynamics are demonstrated with
examples from both the intrapersonal and interpersonal coordination literature that
are interpreted via a conceptual scheme, the causal loops of coordination dynamics
An empirical, behavioral study of interpersonal coordination was conducted to
determine which spontaneous patterns of coordination formed and whether a remnant
of the interaction ensued ("social memory") To assess social memory in dyads, the
behavior preceding and following episodes of interaction was compared In the
experiment, pairs of people sat facing one another and made continuous flexion-extension finger movements while a window acted as a shutter to control
whether partners saw each other's movements Thus, vision ("social contact") allowed
spontaneous information exchange between partners through observation Each trial consisted of three successive intervals lasting twenty seconds: without social contact
("me and you"), with social contact ("us"), and again without ("me and you")
During social contact, a variety of patterns was observed ranging from phase coupling
to transient or absent collective behavior Individuals also entered and exited social
coordination differently In support of social memory, compared to before social
contact, after contact ended participants tended to remain near each other's
movement frequency Furthermore, the greater the stability of coupling, the more
similar the partners' post-interactional frequencies were Proposing that the
persistence of behavior in the absence of information exchange was the result of prior
frequency adaptation, a mathematical model of human movement was implemented
with Haken-Kelso-Bunz oscillators that reproduced the experimental findings, even
individual dyadic patterns Parametric manipulations revealed multiple routes to
persistence of behavior via the interplay of adaptation and other HKB model
parameters The experimental results, the model, and their interpretation form the
basis of a proposal for future research and possible therapeutic applications