The article by Mark Snyder and Steve Gangestad addresses concerns about the Self-Monitoring Scale, a widely used instrument for assessing self-monitoring propensities. Despite its extensive empirical support, some researchers have questioned the scale's validity and reliability, arguing that it does not accurately measure the construct of self-monitoring. The authors examine these concerns through factor analytic investigations and reanalyses of studies, concluding that the scale does indeed measure a meaningful and interpretable causal variable with pervasive influences on social behavior. They propose a new 18-item Self-Monitoring Scale and discuss the evaluation criteria for alternative measures. The article also explores the nature of the general self-monitoring factor, suggesting that it reflects a discrete or quasi-discrete entity with a biological genetic basis. The authors argue that the scale's effectiveness is largely due to the strong effects of this latent causal entity, which is reflected in the same region of the factor space as the general self-monitoring factor. They provide evidence from twin studies and other analyses to support their claims and encourage researchers to consider the external relations of the rotated factors to criterion variables. The article concludes by discussing the implications of these findings for the development and evaluation of psychological measures.The article by Mark Snyder and Steve Gangestad addresses concerns about the Self-Monitoring Scale, a widely used instrument for assessing self-monitoring propensities. Despite its extensive empirical support, some researchers have questioned the scale's validity and reliability, arguing that it does not accurately measure the construct of self-monitoring. The authors examine these concerns through factor analytic investigations and reanalyses of studies, concluding that the scale does indeed measure a meaningful and interpretable causal variable with pervasive influences on social behavior. They propose a new 18-item Self-Monitoring Scale and discuss the evaluation criteria for alternative measures. The article also explores the nature of the general self-monitoring factor, suggesting that it reflects a discrete or quasi-discrete entity with a biological genetic basis. The authors argue that the scale's effectiveness is largely due to the strong effects of this latent causal entity, which is reflected in the same region of the factor space as the general self-monitoring factor. They provide evidence from twin studies and other analyses to support their claims and encourage researchers to consider the external relations of the rotated factors to criterion variables. The article concludes by discussing the implications of these findings for the development and evaluation of psychological measures.