Aims: The Assimilation model argues that therapists should work responsively within the client's therapeutic zone of proximal development (TZPD). This study analyzed the association between the collaborative processes assessed by the Therapeutic Collaboration Coding System (TCCS) and advances in assimilation, as assessed by the
Assimilation of Problematic Experiences Scale (APES).Method: Sessions 1, 4, 8, 12, and 16 of two contrasting cases, Julia and Afonso (pseudonyms), drawn from a clinical trial of 16-sessions emotion-focused therapy (EFT) for depression, were coded according to the APES and the TCCS. Julia met criteria for reliable and clinically significant improvement, whereas Afonso did not.Results: As expected, Julia advanced farther along the APES than did Afonso. Both therapists worked mainly within their client's TZPD. However, Julia's therapist used a balance of supporting and challenging interventions, whereas Afonso's therapist used mainly supporting interventions. Setbacks were common in both cases.