This study examined the effect of anxiety and dissi mulation motivation of job applicants on their perfor mance on an ability test. Two aspects of performance were considered: the total score and the appropriate ness score. Four IRT-based appropriateness indices for detecting aberrant response patterns were employed in this study. The results indicate a negative effect of dissimulation motivation on the performance of low anxiety scorers, with respect to both the total score and the appropriateness score, with a greater effect on the latter. This effect was evidenced by an erratic or aberrant response pattern on the ability test; that is, missing relatively easy items while answering more difficult ones correctly. The results are discussed in light of the diverse interpretations concerning the meaning of Lie scales.