 A second compensatory tactic is the adoption of alternative periodizations. This involves choosing different characters to construct new temporal partitions, thereby facilitating the observation of variation with respect to characteristics previously stabilized in the normal stage periodization. These alternative periodizations often divide a subset of developmental events according to processes or landmarks that differ from those used to construct the normal stages, and they may not map one-one onto the existing normal stages, especially if they encompass events beyond the trajectory from fertilization to a sexually mature adult. This lack of isomorphism between periodizations also will be manifested if different measures of time are utilized, whether sequence (event ordering) or duration (succession of defined intervals), and whether sequences or durations are measured relative to one another or against an external standard, such as absolute chronology (Reiss 2003; Colbert and Rowe 2008). These incompatibilities prevent assimilating the alternative periodizations into a single, overarching staging scheme. In all of these cases, idealization is involved and therefore each new periodization is subject to the liabilities of ignoring kinds of variation. However, alternative periodizations require choosing different characters to stabilize and typify when defining its temporal partitions, which means different kinds of variation will be exposed than were previously  observable.[23]