Abstract Seven experiments were run in which speed of sorting decks of stimulus cards was measured. Stimuli were constructed from two dichotomous dimensions, used either alone, correlated, or orthogonally. Sorting was always into two categories defined by the levels of one dimension. The experiments differed in the nature of the stimulus dimensions. Value and chroma of single Munsell chips and the horizontal and vertical positions of a dot gave results which show facilitation with correlated stimulus dimensions and interference with orthogonal dimensions. Such dimensions, which also produce a Euclidean metric in direct stimulus scaling, are termed integral. Value and chroma of separate Munsell chips, as well as size of circle and angle of diameter, gave results which show little or no facilitation or interference. Such dimensions, which also produce a city-block metric in direct stimulus scaling, are termed nonintegral.