The promise of self-determination theory to study the therapist-client relationship in speech-language treatment.

This study aims at examining the therapist-client relationship in speech-language treatment and its relationships with clients' motivation from the perspective of Self-Determination Theory (SDT). It adds to the current literature by relying on observations as well as client perceptions of the therapists' interaction style and by studying three different age groups of adults (>18 years old), adolescents (12-18 years old) as well as children ( 12 years old), and 2) 21 SLPs (100 % female) and 44 ICDs (50 % girls; <12 years) were recruited for this cross-sectional study. After engaging in a treatment session, ICDs responded to a set of validated questionnaires measuring the SLPs' motivating style, their need-based experiences and motivation towards the treatment. Moreover, each treatment session was observed. Both client-reported as well as observational measures show that SLPs more strongly evince an autonomy-supportive (i.e. motivating) when compared to a controlling (i.e. demotivating) style to the benefit of their clients' motivation. The display of empathy was the most frequently observed strategy. SLPs regularly provided rationales, choices, and opportunities for clients to experiment. However, these behaviors were more frequent in younger compared to older clients. With the younger clients, SLPs frequently used effort-contingent rewards, which is considered a controlling strategy in SDT. Results showed that motivational benefits may be expected if SLPs rely on an autonomy-supportive rather than a controlling style. This study provides a valuable starting point for an SDT-driven examination of the therapist-client relationship and ICD's motivation in the context of speech-language pathology.