In Hare’s initial research, he conducted a factor analysis on a large sample of prisoners who had been administered the PCL-R. Factor analysis identifies scale items that cluster together and is used to create subscales of a measure. Two factors were identified, the interpersonal/affective factor (factor 1) and the socially deviant lifestyle factor (factor 2). In 2003, Hare modified his original model with a new 4-factor model. Factor 1 was divided into an interpersonal factor (impression management, grandiosity, pathological lying, and manipulativeness) and an affective factor (lack of remorse, shallow affect, callous/lacking empathy, and failure to acknowledge responsibility). Factor 2 was divided into a lifestyle factor (stimulation seeking, parasitic, lacking goals, impulsive, and irresponsible) and an antisocial factor (aggressive, early behavior problems, serious criminal behavior, engagement in different types of crimes). Other authors have proposed a 3-factor model, dividing Factor 1 as Hare did, but keeping Factor 2 as a behavioral factor. Over the years, new instruments similar to the Hare PCL-R have been developed and have yielded similar factor structures.