Although frontline customer service employees play a vital role in many firms, their part in service delivery is often underappreciated. The interaction between frontline employees and customers creates an impression of what is to come in the service experience. A key question is whether this interaction spills over to other unrelated aspects of the business. We conduct a quasi-experiment across two medical clinics, one of which had its frontline employees trained to improve their interpersonal skills. We find that not only does the training create positive perceptions of the service provided by frontline employees, but also increases perceptions of service quality attributes not related to these employees. That is, customer perceptions of the interpersonal skills of frontline employees "spillover" to other service quality attributes. However, this spillover effect does not impact all service attributes uniformly; rather, it is restricted to only credence attributes which customers find difficult to evaluate. We term this a selective halo effect. This finding demonstrates that customer perceptions of the interpersonal skills of frontline employees extend well beyond the range in which they perform their expected duties. Our article builds on attribute evaluability theory and information economic theory by demonstrating the existence of a selective halo effect. Further, we develop a classification system that managers can use to predict which attributes are most likely to be influenced by a selective halo effect. We encourage managers to think of frontline employees as "barometers of the business," and to invest in continued training for these key personnel.