Trainees' knowledge gains represent an important outcome in human resource development. In this research, we tested a model examining the joint influence of social desirability (impression management, self-deception) and motives (need for power, need for approval) on trainees' self-reported knowledge gain. We conducted a study with respondents who reported information related to individual differences and took a training program and reported their knowledge gain in domains that were both related and unrelated to the training program. Trainee unrelated knowledge gain was a function of the "joint" influence of individual "predispositions" (to impression manage or engage in self-deception) and "motives" (need for power, approval). Our findings suggest that impression management and self-deception are insufficient to influence respondents' reports of unrelated knowledge but do yield predictable patterns when examined with respondents' motives. We discuss these results and implications for human resource development research and practice.