This complementary association is met with in a striking manner, when a real assimilation is hindered by the associated elements belonging to different senses. In this case the difference in sense-quality erects, as it were, a partition-wall, which prevents the unobservable union of the elements. But at the same time even then close combinations can be formed, which at the operation of a sense-impression immediately reproduce the associated sensations of another sense. For example, we often observe in silent reading weak clang-images of the words, to which are joined slight movements of the articulation-organs, or at least indications of such movements. At the sight of a musical instrument we often perceive in ourselves a weak auditory sensation of its clang; the sight of a gun will often give rise to a weak sound sensation, or if we hear the gun fired, to a reproduced visual image, and so forth. Such associations of disparate senses are called complications. They form an important supplement to the associations, since together with these they essentially determine the ideational process in consciousness. Such a co-operation of assimilations and complications is seen in the most striking manner in those processes of association which in ordinary life are called "recognitions," or, if the scope of the region of association over which the recognition stretches is indefinitely larger, are called "cognitions." We recognise, for example, an acquaintance, whom we have not seen for a long time. We know a table as a table, although we may never have seen the particular table in question before. We can do this by means of the indefinite number of associations with other tables, which the image of the table in question gives rise to. From what we have said above, it is at once obvious that all such recognitions or cognitions are nothing more than assimilations. The usual expression (to know or to be cognisant of) must not tempt us to look upon the process as a logical process, as an act of "knowledge." An act of knowledge may possibly follow a process of pure associative assimilation, if we afterwards try to account for the motives of the same. But the processes themselves, as they continually occur and make up an important part of our sense-experience, are pure associations. To place in them any acts of judgment or of reflection, as is customary in the scholastic psychology of ancient and modern times, can only serve to disguise the real psychological character of these processes. Among the associations called recognitions, only those are of special interest in which the consummation of the assimilation process is in any way hindered, either because the perceived object has but seldom been met with, or because it has undergone changes since a previous perception of it. For example it may, as is well known, take a long time before we recognise a friend, who meets us unexpectedly after many years' absence. If we