Researchers have studied common factors in detail. Grencavage and Norcross (1990) identified 35 common factors in published sources. The identified common factors were categorized into five main groups: client characteristics, therapist qualities, change processes, treatment structures and relationship elements. Examples of some of the common factors included within these broad categories are persuasion, a healing setting, engagement, the use of rituals and techniques, suggestion, and emotional learning. Tracey "et al." 2003, examined deeper relationships among the categories and common factors. They concluded that there are two dimensions of therapy: feeling and thinking. Within each of the two dimensions are three clusters: bond, information, and role.