In-session emotional experiencing in brief psychotherapy conducted by trainee psychologists: process, alliance, and the role of therapist persuasiveness.

Despite the recognition of emotional experiencing as a key change factor in psychotherapy, gaps remain regarding how clinical training influences this dimension, particularly in brief interventions conducted by trainees, and preliminary process data on this phenomenon in Portuguese clinical training contexts are scarce. This study examined emotional experiencing in brief psychotherapy conducted by trainee psychologists undergoing structured experiential training with deliberate practice, analyzing whether patients show a progressive increase in experiential depth across sessions, whether higher levels of emotional experiencing are associated with stronger therapeutic alliance and greater symptom reduction, and whether therapists' persuasiveness predicts patients' emotional experiencing at different session moments. A quantitative repeated measures design was adopted with 5 trainee psychologists and 15 adult patients in a university clinic. Four sessions per patient were analyzed by three independent researchers using standardized measures: the Outcome Questionnaire-45 (OQ-45), the Working Alliance Inventory - Short Revised (WAI-SR), the Experiencing Scale (EXP), and the Therapist Persuasiveness Rating Scale (TPRS). Mixed linear models were then applied to assess longitudinal changes and relationships among variables. A significant reduction in psychological distress and an increase in therapeutic alliance indices, particularly in the tasks and bond dimensions, were observed. No significant changes were found in the depth of emotional experiencing, nor robust associations of this variable with symptom improvement or alliance, except for a marginal negative relationship between goal consensus and modal emotional experiencing. These findings suggest a stability of emotional experiencing in brief intervention contexts, highlighting the central role of collaborative processes in clinical change.