Main effects of Expectancy Cue on reported pain and Task-Incentive and Expectancy Cues on visual discrimination task performance.

<p>A. Expectancy effects on pain. There was a main effect of Expectancy Cue (high vs. low) on pain reports during the critical moderate pain stimulation trials, corresponding to Path <i>c</i> in our mediation model (p<.001) B. <b>Visual discrimination performance as a function of Task-Incentive Cue and Expectancy Cue.</b> There was a main effect of Visual Task Incentive Cue on visual discrimination task performance such that participants performed worse on the visual discrimination task when performance on the heat discrimination task was preferentially rewarded (p = .09 one-tailed). We found no cue-related interactions on visual discrimination task performance, though there was a trend towards reduced visual task performance with the combination of high pain expectancy and focus on the heat discrimination task (p = .11).</p

Mediation path coefficients¹.

1<p>This table presents results from the multi-level mediation analyses presented in <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0038854#pone-0038854-g001" target="_blank">Figure 1</a>. Values reflect mean path coefficients, with standard errors of the mean in parentheses.</p>***<p> = p<0.001;</p>**<p> = p<0.01;</p>*<p> = p<0.05;</p><p>⊥ = p = 0.058.</p><p>n/a values reflect the fact that those paths were not defined because we included only trials at one level of the independent variable for that path.</p

Expectancy and task incentive effects on pain and somatic focus.

<p>A. <b>Mediation Model Results:</b> There were main effects of: 1) Expectancy Cue (high vs. low) on Somatic Focus (Path <i>a</i>); 2) Somatic Focus on pain ratings (Path <i>b</i>); 3) Expectancy cue on pain ratings (Path <i>c</i>); 4) Task-Incentive Cue on Somatic Focus (Path <i>d)</i>; and 5) Task-Incentive cue on pain ratings (Path <i>e</i>) (see below for details of main effects; full statistics are presented in <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0038854#pone-0038854-t001" target="_blank">Table 1</a>). Expectancy effects on pain reports were mediated by changes in somatic focus (<i>c – c’</i>) with a negative mediation effect, indicating that increases in somatic focus partially suppressed the pain-intensifying effects of high pain expectancy (p<0.05). The effect of Task-Incentive cue on pain was mediated by changes in somatic focus (<i>e – e’)</i> (p<0.05). These results indicate that incentivizing the heat discrimination task reduced pain by increasing somatic focus. B. <b>Heat discrimination performance as a function of Task-Incentive Cue and Expectancy Cue.</b> Main effect of Task-Incentive Cue on Somatic Focus (corresponding to Path <i>d</i>): Participants performed at chance (dashed line) when visual task was incentivized, and above chance when heat-discrimination task was incentivized (p<0.001). Main effect of Expectancy Cue (high vs. low) on Somatic Focus (Path <i>a</i>): participants performed better on the heat discrimination task when they expected High pain (p<0.05). There was a significant interaction (dashed arrows in <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0038854#pone-0038854-g002" target="_blank">Figure 2A</a>) between Task-Incentive Cue and Expectancy Cue, such that heat discrimination task performance was better under High pain expectancy (p<0.001), while effects under Low pain expectancy were marginally significant (p = 0.03 one-tailed). C. <b>Pain ratings as a function of Task-Incentive Cue and Expectancy Cue.</b> There was a main effect of Expectancy Cue (corresponding to Path <i>c</i>), such that participants reported less pain when medium heat was preceded by low-pain cues, relative to high-pain cues (p<0.001). There was also a main effect of Task Incentive Cue (Path <i>e</i>), such that participants reported less pain during moderate-pain trials when they were preferentially rewarded for performance on the heat discrimination task, relative to the visual discrimination task (p<0.01). There was also a main effect of Somatic Focus (Path <i>b</i>), such that somatic focus reduced pain (p<0.001).</p