The saltus model was developed in dichotomous form by Wilson (1989), and expanded to polytomous form by Draney (1996) as a
method for detecting and analyzing discontinuities in performance that are hypothesized to occur as a result of rapidly occurring
person growth (e.g.,Fischer, Pipp, & Bullock, 1984). Such discontinuities are often theorized to occur as the result of progression
through developmental stages or levels. The most influential such theory was developed by Jean Piaget (e.g., Piaget, 1950;
Inhelder & Piaget, 1958). Although Piagetian theory has been somewhat controversial of late (e.g., Lourenço & Machado, 1996),
there is still a strong interest in stagelike development in a number of areas, including moral and ethical reasoning (e.g.,
Dawson, 2002; Kohlberg & Candee, 1984), evaluative reasoning (e.g., Dawson-Tunik, 2002; Armon, 1984), adult development (e.g.,
Commons et al., 1998; Fischer, Hand, & Russel, 1984), and cognitive development (e.g., Bond, 1995b, a; Bond & Bunting, 1995;
Demetriou & Efklides, 1989, 1994; Hiele, 1986).