It’s not what you said, it’s how you said it: An analysis of therapist vocal features during psychotherapy

Abstract Psychotherapy is a conversation, whereby, at its foundation, many interventions are derived from the therapist talking. Research suggests that the voice can convey a variety of emotional and social information, and individuals may change their voice based on the context and content of the conversation (e.g. talking to a baby or delivering difficult news to patients with cancer). As such, therapists may adjust aspects of their voice throughout a therapy session depending on if they are beginning a therapy session and checking in with a client, conducting more therapeutic ‘work’ or ending the session. In this study, we modelled three vocal features—pitch, energy and rate—with linear and quadratic multilevel models to understand how therapists’ vocal features change throughout a therapy session. We hypothesised that all three vocal features would be best fit with a quadratic function—starting high and more congruent with a conversational voice, decreasing during the middle portions of therapy where more therapeutic interventions were being administered, and increasing again at the end of the session. Results indicated a quadratic model for all three vocal features was superior in fitting the data, as compared to a linear model, suggesting that therapists begin and end therapy using a different style of voice than in the middle of a session.