Objective: We quantified nonverbal synchrony -the coordination of patient's and therapist's movement -in a random sample of same-sex psychotherapy dyads. We contrasted nonverbal synchrony in these dyads with a control condition and assessed its association with session-level and overall psychotherapy outcome. Method: Using an automated objective video-analysis algorithm (Motion Energy Analysis, MEA), we calculated nonverbal synchrony in (N = 104) videotaped psychotherapy sessions from 70 Caucasian patients (37 female, 33 male, mean age = 36.5 years, SD = 10.2) treated at an outpatient psychotherapy clinic. The sample was randomly drawn from an archive (N = 301) of routinely videotaped psychotherapies. Patients and their therapists assessed session impact with self-report post-session questionnaires. A battery of preand post-symptomatology questionnaires measured therapy effectiveness. Results: We found that nonverbal synchrony is higher in genuine interactions contrasted with pseudointeractions (a control condition generated by a specifically designed shuffling procedure). Furthermore, nonverbal synchrony is associated with session-level process as well as therapy outcome: It is increased in sessions rated by patients as manifesting high relationship quality, and in patients experiencing high self-efficacy. Higher nonverbal synchrony characterized psychotherapies with higher symptom reduction. Conclusions: The results suggest that nonverbal synchrony embodies the patients' self-reported quality of the relationship and further variables of therapy process. This hitherto overlooked facet of therapeutic relationships might prove useful as an indicator of therapy progress and outcome. Keywords: nonverbal synchrony, mimicry, imitation, embodiment, coordinated body-movement  Psychotherapy research has repeatedly shown that the therapeutic relationship is a crucial variable for the success of therapy (Orlinsky, Rønnestad, & Willutzki, 2004). This relationship has been assessed with various methods and its association with outcome is empirically well documented (Horvath & Symonds, 1991; Martin, Garske, & Davis, 2000) . Empirical evidence is far less concrete, however, when it comes to specific techniques to establish this therapeutic relationship. What are the ingredients for a good relationship? Experts have suggested that the nonverbal behavior of therapists has a decisive role in relationship formation (e.g. Hall, Harrigan, & Rosenthal, 1995). Most reviewers agree that a therapist's nonverbal behavior influences the quality of the therapeutic alliance (e.g. Philippot, Feldman, & Coats, 2003). Tickle-Degnen and Rosenthal (1990) explicitly addressed rapport as one of the necessary conditions in the development of a successful therapeutic relationship. They describe three nonverbal components that shape rapport: attentiveness, positivity-negativity, and coordination. In the current study, we focused on the aspect of coordinated body-movements between patient and therapist. We will use the term 'nonverbal synchrony' in accordance with Condon and Ogston (1966), who first described the phenomenon of movement coordination between interacting persons as interactional synchrony. Our conceptualization of nonverbal synchrony has three unique features: a) it is a dynamic quality (Bernieri & Rosenthal, 1991), i.e. movement characteristics are assessed, irrespective of the specific postures or gestures displayed; b) it is measured objectively and automatically by a video-computer interface; c) it includes simultaneous movement (Condon and Ogston's definition) as well as time-lagged coordinated movement in a window of ± 5 seconds. The rationale behind our approach to nonverbal synchrony in psychotherapy is based on the nonverbal components of rapport and on the concept of embodiment (e.g. Gallese, 2005). We hypothesize that synchronous body movement is a manifestation of rapport, and ultimately, relationship quality. This perspective on synchrony is not limited to nonverbal behavior: synchrony is a pervasive concept relevant to physics, biology, and the social sciences, hence is found both in living systems and inanimate nature (Ramseyer & Tschacher, 2006; Strogatz, 2003). Synchrony has been conceptualized from both a neural ('mirror neurons' Iacoboni, 2009) and representational point of view ('neuronal coherence' Rodriguez et al., 1999) , as well as from the stance of self-organized behavioral dynamics ('synergetics' Oullier, Guzman, Jantzen, Lagarde, & Kelso, 2008). Nonverbal synchrony can be considered a Gestalt which humans are capable of perceiving on a flexible time basis (Bernieri, Reznick, & Rosenthal, 1988), and which does not reside in any particular behavior (Davis, 1981; Grammer, Kruck, & Magnusson, 1998). Here we have adopted a theoretically neutral concept of movement coordination and were interested in the manifestation of coordinated dynamics, not in specific gestures, postures or any other qualitative information. The dynamical systems view (Newtson, 1994; Schmidt & Richardson, 2008; Tschacher & Dauwalder, 2003 Nonverbal synchrony during interaction has been previously studied in diverse contexts (Bernieri & Rosenthal, 1991; Burgoon, Stern, & Dillman, 1995; Davis, 1982). Synchrony between patient and therapist can manifest itself in a qualitative correspondence between persons: matching of body positions ('congruent body positions ' Charny, 1966; Maurer & Tindall, 1983; Scheflen, 1964; Trout & Rosenfeld, 1980) Bavelas et al., 1987), a common attentional orientation and a similarity in views or roles, which in turn also lead to an increase in liking (Scheflen, 1964; Wallbott, 1996). Interestingly, the term empathy is derived from the German word Einfühlung ("feeling oneself into"), which in its early While many authors have previously suggested that a good relationship is embodied by various forms of synchrony, generalizable empirical evidence from controlled studies in psychotherapy is scarce (Rosenfeld, 1981) . Nonverbal synchrony has been sporadically assessed in psychotherapy sessions (overviews: Hess, Philippot, & Blairy, 1999; Ramseyer, 2008). Most of the early psychotherapy studies, however, were based on single cases and anecdotal accounts (Charny, 1966; Scheflen, 1964) . Furthermore, the majority of empirical research has been conducted in role-played interactions (Trout & Rosenfeld, 1980), in student populations (Koss & Rosenthal, 1997), or via ratings of therapist behavior (Harrigan & Rosenthal, 1983). Dyads involved in real psychotherapeutic interaction have seldom been assessed directly. The current study is based on naturalistic psychotherapy data, implemented a randomized sampling procedure, and controlled for synchrony that might be expected by chance. Our main hypothesis is that if nonverbal synchrony exists in psychotherapy interactions, its manifestations Running head: NONVERBAL SYNCHRONY IN PSYCHOTHERAPY 7 will be more pronounced in psychotherapy than in a control condition of 'pseudointeractions' (interactions generated by shuffled time-structures; as defined in the methods section below). Our second hypothesis is that a positive correlation exists between the amount of nonverbal synchrony and measures of relationship quality assessed immediately after a therapy session. Finally, we hypothesize that nonverbal synchrony is positively associated with the outcome of therapy, as measured by pre-post therapy assessments (pre-to-post outcome) and retrospective therapy success measures (retrospective outcome). Methods and Procedures Participants (N = 70) were 37 women and 33 men (mean age 36.5 years, SD = 10.2, all white Caucasian European ethnicity) treated at the outpatient psychotherapy clinic of the University of Bern, Switzerland. This clinic accepts patients suffering from a wide range of problems and disorders, with the exceptions of psychotic disorders and substance dependency. Patients of this sample belonged to the following main diagnostic groups: 34% anxiety disorders, 29% affective disorders, 37% other diagnoses (11.4% adjustment disorders, 8.6% personality disorders, 17% other disorders). Comorbidity was predominantly found in anxiety disorders (58% comorbid patients) and affective disorders (24%). These percentages were considered representative of the database population of N = 838 cases: 35.1% anxiety disorders; 24.8% affective disorders; 10.5% adjustment disorder; 4.3% eating disorders; 15% no axis-1 disorder. All diagnoses were assessed prior to therapy using the Structured Clinical Interview (SCID; Mean psychotherapy duration per patient was 38.1 sessions (SD = 22.1, range 8 -126). Based on a single-case analysis (Ramseyer & Tschacher, 2008) and further pilot-data (Ramseyer, 2008), an apriori power analysis (1-! = 0.80; " = .05) assuming a correlation of Pearson's r = .35 between nonverbal synchrony and relationship quality, resulted in a minimal sample size of n = 62 patients (124 sessions). The following inclusion criteria were applied to the complete video archive of 301 patients (10,266 sessions): First, only psychotherapy sessions where patient and therapist were of the same gender were included (n = 197 patients; 6,441 sessions). This criterion was based on previous research showing that mixed-gender dyads were less prone to exhibit nonverbal synchrony (Grammer et al., 1998). Second, only sessions with recordings on VHS tape were included for analysis (n = 5,152 sessions). Third, stratification was balanced for gender and phase of therapy (1st third [T1] or 3rd third [T3]). Each dyad thus provided a session from T1 and T3 of the respective therapy, resulting in a total of 160 sessions. Fourth, of these randomly drawn sessions, we selected only those where dyads remained seated throughout, interacting verbally and nonverbally without external constraints on free movement, e.g. through the use of a flip chart or similar device (excluded: 27 sessions). Fifth, overall video-signal quality had to be sufficient for our measure of nonverbal synchrony (excluded: 29 sessions). Application of these inclusion criteria resulted in 104 psychotherapy sessions of 70 dyads: 47 from T1 and 57 from T3 (flow-chart: see Figure W1 , web-appendix). All sessions (average duration 50 min) were recorded using two cameras joined into a split-screen image ( Figure 1A ). In general, therapists (n = 42) conducted sessions once a week, using cognitive-behavioral psychotherapy (Grawe, 2004). Therapists had heterogeneous backgrounds comprising psychologists from a post-graduate training program in psychotherapy
Earlier work measured coordinations in dyadic body movement using Pearson's cross-correlation (CC) REF .
Nonverbal synchrony in psychotherapy: Coordinated body movement reflects relationship quality and outcome.
Journal of consulting and clinical psychology
Journal of consulting and clinical psychology
Psychology Medicine