What Does It Mean To Be Different? A Person-Oriented Perspective

Person-oriented research proceeds from the assumption that individuals differ to the extent that statements that are based on the aggregation of raw scores rarely capture all individuals, if ever. To justify the effort needed for person-oriented research, it needs to be shown where and how individuals differ. Conversely, when aggregate-level statements are intended, it needs to be shown that groups are homogeneous. In this article, it is suggested that ‘to be different’ is specific to the method of analysis used. Within the context of person-oriented research, intra- and interindividual differences can be searched for in the domains of magnitude of scores, structure of scores, causal relations and direction dependence, frequencies of occurrences of patterns of behavior, as well as distances between individuals and groups of individuals. All this can be performed in both, cross-sectional and longitudinal research. The requirements are discussed that data sets must meet for person-oriented research. It is also shown that differences in one domain neither imply nor preclude differences in other domains. Real-world data examples are given that illustrate the nature of differences with respect to each tenet of person-oriented research.