The traditional methods of psychophysical scaling presuppose knowledge of the dimensions of the area being investigated. Since each dimension must be considered separately, no knowledge of the relation between units of the different dimensions is obtained. In many scaling areas, the problem is complex. Often the dimensions themselves or even the number of relevant dimensions are not known. What might appear intuitively to be a single dimension may, in fact, be a complex of several. A number of intuitively given dimensions may be linear combinations of each other. Other dimensions of importance may be completely overlooked.