Effects of Target Prevalence and Speech Intelligibility on Visual Search Performance

Visual search is commonly performed in the control rooms of several industries such as nuclear power plants, flight control, security screening, and monitoring. In this study, the effects of target prevalence and speech intelligibility on visual search performance were investigated. A 2 (target prevalence: low versus high) x 3 (speech transmission index = 0 versus 0.51 versus 0.69) mixed design experiment was conducted. Target prevalence was a betweensubject variable, whereas the speech transmission index was a within-subject variable. A total of 32 participants participated in simulated X-ray screening tasks in different speech intelligibility conditions. Results revealed that both the target prevalence and the speech transmission index level had significant effects on visual search performance. The reaction time was shorter and the miss error rate was higher under low target prevalence condition than in high target prevalence condition. Compared with no speech condition (speech transmission index = 0), the reaction time of the participants increased significantly with the presence of intelligible speech in an acoustic environment. Performance loss was greatest when the speech transmission index was 0.51. The interaction effect of target prevalence and speech transmission index level was also significant. Proper measures should be taken to reduce unfavorable effects of low target prevalence and intelligible speech in acoustic environment on visual search performance in control rooms.