The influence of outcome expectancy on interpretation bias training in social anxiety: an experimental pilot study

Cognitive bias modification for interpretation (CBM-I) trainings have shown positive effects on interpretation bias in both active interpretation bias training conditions and structurally similar control conditions. Outcome expectations have been suggested to contribute to these placebo effects. The goal of this pilot experimental study was to test the feasibility of positive expectancy induction, to gain preliminary insight into whether this has implications for the efficacy of CBM-I training, and to assess the feasibility of recruitment and the overall study design.

Socially anxious individuals aged 18 years and older received a single session (approx. 45 min) of either CBM-I or placebo training preceded by either a positive expectancy induction or no expectancy induction. We first tested whether the expectancy induction had modified participants' expectations of training. We then explored the effects of CBM-I training and expectancy induction on interpretation bias. Finally, we assessed the feasibility of recruitment and further study procedures.

Due to pandemic-related difficulties, fewer participants were recruited than initially planned. Thirty-four (22 females and 12 males) participants were randomly assigned to one of four conditions (interpretation bias training + high expectancy = 10, interpretation bias training + no expectancy = 8, placebo training + high expectancy = 11, placebo training + no expectancy = 5). Participants in the positive expectancy condition had more positive expectations of the training (CBM-I or placebo) than participants in the no expectancy condition. We were unable to conduct the planned 2 × 2 × 2 analysis of interpretation bias due to the small sample size. When looking at these groups individually, we found that participants in the active training condition and participants in the high expectancy condition showed increases in positive interpretation bias and decreases in negative interpretation bias from pre- to post-training, while participants in the placebo and no expectancy conditions showed no change.

These findings suggest that the expectancy manipulation utilized in this study may be adopted by future studies which investigate outcome expectations as an unspecific mechanism of CBM-I. Preliminary analyses suggest that participants' expectations are likely to play a role in the effect of CBM-I training, although these effects require replication in a larger sample. Several observations about the study feasibility were made which could inform future trials.

Retrospectively registered on the August 23, 2022, through the German Clinical Trials Register ( DRKS00029768 ).