Supervision has been referred to as the component of doctoral training that has the greatest impact on the competencies of psychology trainees (Johnson & Stewart, 2000). Nevertheless, there are considerable gaps in the empirical literature examining psychotherapy supervision. One topic that has been particularly ignored in the empirical literature is supervisor development. Considering this, the purpose of the current study was twofold. The first purpose was to examine factors that promote the development of supervisors. The second purpose was to explore how supervisor development impacts supervisor attributes. Supervisors (N = 99) of pre-doctoral interns from APA approved internship sites in counseling and clinical psychology completed a questionnaire that examined types of training in supervision, as well as length of experience as both a supervisor and therapist, the Psychotherapy Supervisory Development Scale (PSDS), the Supervisory Styles Inventory (SSI), and the Working Alliance Inventory—Supervisor (WAI-S). Results indicated that types of training were related to supervisor development. Specifically, it was found that supervisors who had participated in a practicum class on supervision, a combined practicum/didactic class on supervision, or had received supervision of his/her provision of supervision had significantly higher scores on supervisor development than those supervisors who had not. However, experience as a supervisor and experience as a therapist were not significantly related to supervisor development. In addition, supervisors with more varied types of training experiences were significantly more developed that those with fewer training experiences. Results of the second part of the study demonstrated a connection between supervisor development and two components of supervisory style as well as the supervisory working alliance. Specifically, results provided support that both interpersonally sensitive and attractive supervisory styles serve as mediators in the relation between supervisor development and the supervisory working alliance
