The differences described above are largely of a qualitative kind, and could be arranged hierarchically. The popular Bloom taxonomy offers one hierarchy in which knowledge and comprehension underpin ‘higher level’ thinking processes like application, analysis and evaluation (Bloom et al., 1956). Such a hierarchy, however, tends to obscure the possibility of a boot-strapping effect between levels. In attempting to apply a partially developed
understanding, the coherence and structure of that understanding may be enhanced as a consequence. This process may be seen in a novice’s developing grasp of a subject. As engagement continues, more or less isolated and relatively small mental structures are integrated so that a greater coherence develops. Principles, rather than the surface features of situations, begin to govern the novice’s responses. The conditions which determine the legitimate application of knowledge are learned and, as experience accumulates, it plays an increasing part in achieving goals (Glaser, 1990). Collis and Biggs (1989) devised the SOLO taxonomy, which captures something of this by classifying a response according to the evidence it gives about the nature of the mental structure. The taxonomy ranges from no relevant response, through simple structures, to relationships and wider connections of the relationship.