The IMP procedure was identical to the word-sentence association paradigm (WSAP; Beard & Amir, 2009) except participants received feedback about their responses. Participants received positive feedback when they endorsed benign interpretations or rejected threat interpretations of the ambiguous sentences on 100% of trials and negative feedback when they endorsed threat interpretations or rejected benign interpretations on 100% of trials. This feedback manipulation was intended to reinforce a benign interpretation bias and extinguish the threat interpretation bias. Participants completed two blocks of 110 training trials in each session. Participants who completed Set A during the WSAP assessment saw Set B during the IMP and vice versa. Each IMP session lasted approximately 20 min.

The ICC was identical to the IMP, except that participants received positive feedback when they endorsed threat interpretations on half (50%) of the trials and negative feedback when they endorsed threat interpretations for the remaining half (50%) of trials. This frequency was the same for benign interpretations. Thus, the control group was reinforced equally for making threat and benign interpretations. The ICC was not intended to change interpretation significantly in either direction.

The IMP protocol includes twelve 30-min sessions delivered over a 6-week period. Each session will comprise 220 trials. In each trial, participants will first see either a non-threat or a threat (e.g. "graceful" or "clumsy") word on the computer screen. They will then see an ambiguous sentence (e.g. "You dance at the party") and will be asked to indicate if the word and sentence were related by pressing a corresponding key. Participants will receive positive feedback (i.e., "You are correct!") when they endorse a non-threat interpretation or reject a threat interpretation of an ambiguous sentence. Participants will receive negative feedback (i.e., "You are incorrect.") when they endorse a threat interpretation or reject a non-threat interpretation of an ambiguous sentence.

Our primary outcome measure was the clinician-administered LSAS (Liebowitz, 1987), a 24-item scale that provides separate scores for fear and avoidance of social interaction and performance situations. LSAS scores range from 0 to 144. The LSAS has strong psychometric properties (Heimberg et al., 1999) and is arguably the gold-standard outcome measure in treatment research in SAD (e.g., Clark et al., 2006; Heimberg et al., 1998). Higher scores indicate more severe symptoms.

Our secondary outcome assessment of social anxiety symptoms was the Social Phobia and Anxiety Inventory (SPAI; Turner, Beidel, Dancu, & Stanley, 1989), a 45-item self-rated measure that assesses the cognitive, behavioral, and somatic dimensions of SAD. SPAI scores range from 45 to 315, with higher scores indicating more severe symptoms. Previous research suggests that the SPAI has sound psychometric properties (e.g., Turner et al., 1989). Internal consistencies for these measures in the current sample were satisfactory.

The IMP procedure was identical to the word-sentence association paradigm (WSAP; Beard & Amir, 2009) except participants received feedback about their responses. Participants received positive feedback when they endorsed benign interpretations or rejected threat interpretations of the ambiguous sentences on 100% of trials and negative feedback when they endorsed threat interpretations or rejected benign interpretations on 100% of trials. This feedback manipulation was intended to reinforce a benign interpretation bias and extinguish the threat interpretation bias. Participants completed two blocks of 110 training trials in each session. Participants who completed Set A during the WSAP assessment saw Set B during the IMP and vice versa. Each IMP session lasted approximately 20 min.

Our primary outcome measure was the clinician-administered LSAS (Liebowitz, 1987), a 24-item scale that provides separate scores for fear and avoidance of social interaction and performance situations. LSAS scores range from 0 to 144. The LSAS has strong psychometric properties (Heimberg et al., 1999) and is arguably the gold-standard outcome measure in treatment research in SAD (e.g., Clark et al., 2006; Heimberg et al., 1998). Higher scores indicate more severe symptoms.

The IMP procedure was identical to the word-sentence association paradigm (WSAP; Beard & Amir, 2009) except participants received feedback about their responses. Participants received positive feedback when they endorsed benign interpretations or rejected threat interpretations of the ambiguous sentences on 100% of trials and negative feedback when they endorsed threat interpretations or rejected benign interpretations on 100% of trials. This feedback manipulation was intended to reinforce a benign interpretation bias and extinguish the threat interpretation bias. Participants completed two blocks of 110 training trials in each session. Participants who completed Set A during the WSAP assessment saw Set B during the IMP and vice versa. Each IMP session lasted approximately 20 min.