Lists, inventories, groups, taxonomies and frameworks	39

groups drawn from objects in the real world but they lack (at least, for us) a common theme. On the other hand, igneous, sedimentary, and metamorphic are mutually exclusive geological groups of the same objects of study, rocks. (In this instance, the taxonomy is also comprehensive in that it describes all naturally-occurring rocks.) On this basis, a taxonomy is a strong form of grouping in which the groups clearly relate to one another. ‘Taxonomy (classification) consists of working out a system of mental pigeon holes in which every conceivable species [of thinking] would have an appropriate place’ (Bowler, 1992, p. 102).

A taxonomy is useful because it can facilitate the mental representation of a field. In doing so, it aids study by dividing a field into units that can be related to other units (Bowler, 1992, p. 93) and a comprehensive taxonomy ‘is the best inventory tool a researcher has’ (Bailey, 1994, p. 12).

There are, however, some caveats. A taxonomy is manufactured and may not reflect reality, nor may it be the only useful way of classifying the objects of study. Objects of study can be classified in many ways and it is not always clear which way is ‘best’. On occasions, objects of study may be entirely discrete, so that the divisions between the groups are sharp. But, with many groups, the divisions between them may be arbitrary and this can be overlooked. Taxonomies may seduce people into thinking in terms of sharp divisions between its groups. While taxonomies reduce a field to manageable proportions (for thinking), when they reduce the field to a very small number of groups, they can be simplistic. On the other hand, a large number of groups may reflect reality better but can be unmanageable. Finally, to classify is not to explain.

Utility

Provided that the caveats are kept in mind, taxonomies can be useful. To be useful, a classification or arrangement of any kind needs to suit its purpose. For instance, classification in biology is used for two different purposes: identification and making natural groups. The modern system of classifying species by grouping together those which display a clear relationship to one another was developed by

40 Frameworks for Thinking

Ray, Linnaeus and others. A taxonomist in biology ‘sees’ generic attributes and differences of a specimen and allocates it to a group of like organisms (Losee, 1993, p. 8). The description serves to identify other specimens. Exemplars drawn from the group help to locate other organisms in the taxonomy. Unlike organisms, thinking skills, learning outcomes and teaching objectives are intangible. The first problem is to identify what sorts them in a meaningful way that is also useful to, for instance, teachers, curriculum planners and test developers.

Taxonomists may begin with a vast array of objects of study and progressively sort them into groups. This might be done empirically, trying different attributes until ones that discriminate between the objects are found. This process of group finding may be supported by, for example, cluster analysis. Another approach is to have theory or informed conjecture predict groups and then to see if they work. In the social sciences, however, constructs and concepts are such that meaningful groups that are entirely distinct do not always arise. From a practical point of view, this is not always a problem, as these groups can still be useful.

Taxonomies and models

Although a taxonomy alone is a descriptive framework, when it is shaped by a model, it can become a theoretical framework that explains and predicts. An explanatory model is a construct that behaves in some way like the phenomenon it represents. For example, the telephone exchange and the digital computer have provided explanatory models of the mind (see Gregory, 1987). In a real sense, a model brings a theory to the phenomenon under study (Anderson, 1983, pp. 12–13). In instructional technology, Hannafin and Hooper (1989) constructed a model to support the design of computer-based instruction. In essence, it focuses the designer’s thoughts on retrieval, orientation, presentation, encoding, sequencing and context. Underpinning this with a taxonomy that relates the concepts makes a theoretical framework with practical application. Similarly, Gagne´ drew together a classification of types of learning (as outcomes) and a conceptual structure (the internal and external conditions of instruction) to produce a theoretical framework to guide instructional design (see Seels, 1997).