Multidimensional scaling analyses of two construction-related tasks

Representations involved in two construction-related tasks were analyzed by multidimensional scaling (MDS), a statistical technique that allows the di mensions of internal representations to be derived from empirically obtaine d judgment data. The tasks involved judgments of how similar two objects we re and how well they fitted together; these judgments are related to copyin g and assembly abilities that are impaired in constructional apraxia. Analy ses of numerical subjective ratings and response times for these judgments showed that within the same set of geometric objects, different shape-relat ed properties were emphasized under different task conditions. The similari ty judgment depended most on a representational dimension related to enclos ure of space, while the fit judgment depended to a greater extent on a dime nsion related to the objects' symmetry properties. This pattern of results was found in both subjective ratings and response times, as analyzed by MDS and by confirmatory classical statistics. The findings suggest that constr uction-related tasks depend on representations that are context-dependent, and that MDS may be useful in a variety of settings as an intermediate-leve l tool for analyzing representations related to context-specific abilities.