Findings from the past two decades of interpersonal sensitivity research presented a big surprise to the researchers who were working in this area. These findings, at first suggestive and then unmistakably clear, showed that scores on various interpersonal sensitivity measures were not as stable as scores on other measures of cognitive ability (for example, IQ scores) seemed to be. The accumulating data further suggested that differences in situationally-evoked motivational states were the most probable cause of these variations in interpersonal sensitivity. This book examines this discovery and how it has completely changed the research agenda for those working in this field of study.