RESUMO
(1) Background: Many studies have used a well-known social exclusion task, namely Cyberball, to assess the psychophysiological reactions to ostracism in laboratory settings. However, this task has been recently criticized for its lack of realism. Instant messaging communication platforms are currently central communication channels where adolescents conduct their social life. These should be considered when recreating the emotional experiences that fuel the development of negative emotions. To overcome this limitation, a new ostracism task, namely SOLO (Simulated On-Line Ostracism), recreating hostile interactions (i.e., exclusion and rejection) over WhatsApp was developed. The aim of this manuscript is to compare adolescents' self-reported negative and positive affect, as well as physiological reactivity (i.e., heat rate, HR; heart rate variability, HRV) exhibited during SOLO to Cyberball. (2) Method: A total of 35 participants (Mage = 15.16; SD = 1.48; 24 females) took part in the study. The first group (n = 23; transdiagnostic group), recruited at an inpatient and outpatient unit of a clinic for children and adolescent psychiatry, psychotherapy, and psychosomatic therapy in Baden-Württemberg (Germany), reported clinical diagnoses linked with emotional dysregulation (e.g., self-injury and depression). The second group (n = 12; control group), recruited in the district of Bavaria and Baden-Württemberg, had no pre-existing clinical diagnoses. (3) Results: The transdiagnostic group showed higher HR (b = 4.62, p < 0.05) and lower HRV (b = 10.20, p < 0.01) in SOLO than in Cyberball. They also reported increased negative affect (interaction b = -0.5, p < 0.01) after SOLO but not after Cyberball. In the control group, no differences in either HR (p = 0.34) or HRV (p = 0.08) between tasks were found. In addition, no difference in negative affect after either task (p = 0.83) was found. (4) Conclusion: SOLO could be an ecologically valid alternative to Cyberball when assessing reactions to ostracism in adolescents with emotional dysregulation.