In an experiment with Holmgren wool samples, patients with cerebral lesions were able to match only the identical skeins. With cardboard figures, the instruction to sort was first understood by the patients in the sense of to build, to make patterns; only through appropriate coercive conditions did the quality of color, form, or size become effective. Although the patients achieved some kind of arrangement of the figures, they could not volitionally give up the kind of arrangement which they had just achieved in favor of another arrangement. All theories of abstraction have this basic point of view in common: the reaction to "partial conformities of several objects of perception" must be preceded by a stage in which these "precepts" are experientially present as definite objects with a definite number of well-defined given properties. The actual feat of abstraction consists in either voluntarily or involuntarily singling out from all the given contents. (See II: 62, 63.) (PsycINFO Database Record (c) 2006 APA, all rights reserved)