| This dissertation developed and tested theoretical models concerning the effects of similarity on extra-role behavior in on-going work groups. Similarity Attraction Theory and Self Attention Theory were used as two competing frameworks to explain the relationships in the models. In addition, Behavior Plasticity Theory was used to predict the effect of self-esteem. The theoretical models extend prior research by including two forms of extra-role behavior: helping and voice. In addition, similarity was conceptualized in two different manners: actual similarity and experienced similarity.; The models and hypotheses were tested in a field study of 581 employees from 93 work groups. Data were collected from employees, their peers, and their supervisors at two times, six months apart. Results of the data analysis demonstrated overall support for the models. Extra-role behavior was differentiated from in-role behavior both conceptually and empirically. Helping extra-role behavior was positively related to actual similarity and experienced similarity as predicted by Similarity Attraction Theory. Demographic similarity influenced experienced similarity and experienced similarity mediated the effects of actual similarity on helping extra-role behavior. Voice extra-role behavior was positively related to actual similarity and experienced similarity. Contrary to expectations, self-esteem was a stronger predictor of both helping and voice than experienced similarity.; The dissertation also examined the relationship between extra-role behavior and group effectiveness. Analysis of cross-sectional data on 89 groups demonstrated a positive relationship between extra-role behavior and group effectiveness at time one. Longitudinal data on twenty-nine groups, however, failed to support a lagged effect of extra-role behavior at time one on group effectiveness at time two.; Examination of these research questions is important because the models that were tested were theory driven. Accordingly, results enhance our understanding of Similarity Attraction Theory, Self Attention Theory, and Behavior Plasticity Theory. Results of this research are also important given the increasing emphasis that organizations are placing on innovation and discretionary behavior as well as the increasing diversity of the workforce. |
