Applying Idiographic Research Methods : Two Examples

Idiographic methods focus on time-dependent variation within a single individual (intra-subject variability) in contrast to group-level relationships (inter-subject variability) that may yield different results. Equivalent results occur only if two, probably unrealistic, conditions specified by Ergodic Theorems are met: (1) Each trajectory follows the same dynamic laws, and (2) Each trajectory has equal mean levels and serial dependencies. Two studies illustrate the difficulty of meeting ergodic conditions and unique types of research questions that can be addressed by idiographic methods. The first example involves longitudinal smoking patterns. The second study involves reactions of autistic students to environmental stressors. Neither study supports the ergodic conditions. Both studies illustrate research questions unique to idiographic methods, which produce information that is likely to be distinct from that provided by group-based methods.