If then the associations which arise quite freely are determined in this way and belong to some definite context, we are surely justified in concluding that associations attached to one single stimulus-idea must be equally narrowly conditioned. Examination shows as a fact that they are not only attached in the first place to the stimulus-idea which we have provided for them, but that they are also dependent, in the second place, on circles of thoughts and interests of strong affective value (_complexes_, as we call them) of whose influence at the time nothing is known, that is to say, on unconscious activities. Associations attached in this way have been made the subject of very instructive experiments, which have played a notable part in the history of psycho-analysis. Wundt’s school originated the so-called ‘association-experiment,’ in which the subject of the experiment is bidden to reply to a given ‘stimulus-word’ as quickly as possible with whatever ‘reaction-word’ occurs to him. The following points may then be noted: the interval which elapses between the sounding of the stimulus-word and of the reaction-word, the nature of the latter, and possibly any mistake which comes in when the same experiment is repeated later, and so on. The Zurich School, under the leadership of Bleuler and Jung, arrived at the explanation of the reactions to the association-experiment by asking the person experimented upon to throw light upon any associations which seemed at all remarkable, by means of subsequent associations. In this way it became clear that these unusual reactions were most strictly determined by the complexes of the person concerned. By this discovery Bleuler and Jung built the first bridge between experimental psychology and psycho-analysis. Having heard this you may possibly say: “We admit now that free associations are subject to determination and not a matter of choice, as we thought at first, and we admit this also in the case of associations to the elements of dreams. But it is not this that we are bothering about. You maintain that the association to each element in the dream is determined by some mental background to this particular element, a background of which we know nothing. We cannot see that there is any proof of this. Naturally we expect that the association to the dream-element will be shown to be conditioned by one of the complexes of the dreamer, but what good is that to us? That does not help us to understand the dream; it merely leads to some knowledge of these so-called complexes, as did the association-experiment; but what have these to do with the dream?”