The Alliance-Outcome Correlation: Is There a Halo Effect?

The working alliance between therapists and their clients is consistently associated with the outcome of the therapy such that symptom improvement is more likely when the alliance is rated more positively. However, this correlation could be inflated by biased alliance ratings. This study examined the experimental effect of outcome knowledge on observer ratings of the therapeutic alliance. Consistent with the halo effect, it was hypothesized that positive outcome knowledge would yield higher alliance ratings and negative outcome knowledge would yield lower alliance ratings relative to the control group. All participants (N = 168) watched the same video of a therapy session, followed by a randomized voiceover in which they either heard a detailed account of a positive outcome, negative outcome, or received no outcome information, before rating the alliance. Analyses revealed that participants in the negative condition rated the alliance significantly lower than participants in the positive and control groups. Findings were consistent with the halo effect suggesting that knowledge of a negative therapeutic outcome may bias observers' ratings of the alliance, which may have implications for psychotherapy researchers' coding procedures. Further questions about the validity of alliance ratings from other sources are discussed. Public Health Significance Statement In this study impressions of therapy outcomes influenced perceptions of the therapeutic relationship rated by novice observers. These findings raise concerns about alliance measurement and validity. Researchers should keep coders blind to client outcome information when rating the working alliance to avoid biasing ratings.