Catching a (sine) wave: Temporal dynamics of nonverbal synchrony in social anxiety disorder

Individuals with social anxiety disorder (SAD) experience a range of interpersonal problems and studies have found that nonverbal synchrony (the coordination between interaction partners' movements) may be impaired in dyads in which one individual has SAD (Asher et al., 2020). In the present study, we examined the temporal dynamics of nonverbal synchrony during "getting aquatinted" conversations of individuals with and without SAD. Specifically, participants (n = 146) formed either SAD dyads (dyads in which one individual had SAD and the other did not; n = 37 dyads), or control dyads (dyads in which both individuals did not have SAD; n = 36 dyads). Dyads were randomized to either small talk or closeness-generating (i.e., intimate) conversations. We found that during conversations, nonverbal synchrony followed a repeating pattern of increases and decreases that was best modeled by a sinusoidal wave (explained variance = 63.74 %). We found significant Diagnosis × Social Context interactions in the temporal dynamics of nonverbal synchrony (i.e., in the parameters of sine waves). Specifically, we found that for SAD dyads (but not control dyads), the average sine wave amplitude which indicates increases and decreases in nonverbal synchrony was greater during small talk conversations compared to closeness-generating conversations. In addition, we found that among control dyads (but not SAD dyads), the average vertical offset of sine waves (i.e., the average level of nonverbal synchrony) during closeness-generating conversations was greater compared to small talk conversations. The findings are interpreted within the context of the social anxiety literature as capturing two distinct social-anxiety related processes, and suggest that when examined temporally (rather than averaged), nonverbal synchrony may be an important implicit biomarker of SAD.