Quantifying behavior often involves using variables that contain measurement errors and formulating multiequations to capture the relationship among a set of variables. Structural equation models (SEMs) refer to modeling techniques popular in the social and behavioral sciences that are equipped to handle multiequation models, multiple measures of concepts, and measurement error. This work provides an overview of latent variable SEMs. We present the equations for SEMs and the steps in modeling, and we provide three illustrations of SEMs. We suggest that the general nature of the model is capable of handling a variety of problems in the quantification of behavior, where the researcher has sufficient knowledge to formulate hypotheses.error in variables | factor analysis | path analysis | LISREL | covariance structures A mong the many problems in quantifying behavior are the challenges presented by the multiple equations to study and the difficulty of accurately measuring key concepts. For instance, scientists might be interested in general arousal and how it relates to more specific forms of arousal, or researchers might want to analyze quality of sleep and it relationship to different forms and intensities of pain. Arousal, quality of sleep, pain intensity, and numerous other variables are difficult to measure without considerable measurement error. Additionally, studying how several or more of these difficult to measure latent variables relate to each other is an even more arduous task when the multiequation nature of the problem is included.Ignoring these issues leads to inaccuracy of findings. Ignoring the measurement error in arousal or pain data, for instance, leads to inaccurate assessments of effects. Therefore, our assessment of perception of pain on quality of sleep is unlikely to be correct if we do not take account of the measurement error. We might have several ways to measure the same latent arousal variable and not be sure how to incorporate these ways into the model. Also, if we ignore the indirect effects of one variable on another variable and concentrate only on the direct effect, we are more likely to be mistaken in our assessment of how one variable affects another variable.Structural equation models (SEMs) refer to modeling techniques popular in the social and behavioral sciences that are equipped to handle multiequation models, multiple measures of concepts, and measurement error. This general model incorporates more familiar models as special cases. For instance, multiple regression is a special form of SEM, where there is a single dependent variable and multiple covariates and the covariates are assumed to be measured without measurement error. ANOVA is a another specialization where the covariates are assumed to be dichotomous variables. Factor analysis is yet another special form of the latent variable SEM. Here, we assume that we have multiple indicators that measure one or more factors and that the factors are permitted to correlate or not correlate. Recursive models, nonrecursive model...