The above described new experiments suggest to me that this inhibition of equal or similar impressions is found unequally developed in different individuals. They possess a different tendency to temporary exhaustion of psychophysical dispositions. There are evidently persons who after they have received an impression are unable immediately to seize the same impression again. Their attention and their whole inner attitude fails. But there are evidently other persons for whom, on the contrary, the experience of an impression is a kind of inner preparation for arousing the same or a similar impression. In their case the psychophysical dispositions become stimulated and excited, and therefore favor the repetition. If, as in our experiments, the task is simply to judge the existence of equal or similar impressions without any strain of attention, the one group of persons must underestimate the number of the equal impressions because many words are simply inhibited in their minds and remain neglected, the other groups of persons must from their mental dispositions overestimate the number of similar words. From here we have to take one step more. If these two groups of persons have to perform a task in which it is necessary that not a single member of a series of repetitions be overlooked, it is clear that the two groups must react in a very different way. Now a perfect perception of every single member is forced on them. Those who grasp equal impressions easily, and who are prepared beforehand for every new repetition by their inner dispositions, will follow the series without strain and will experience the repetition itself with true satisfaction. On the other hand, those in whom every impression inhibits the readiness to receive a repetition, and whose inner energy for the same experience is exhausted, must feel it as a painful and fatiguing effort if they are obliged to turn their attention to one member after another in a uniform series. This mental torture is evidently the displeasure which such individuals call the dislike of monotony in their work. Whether this theoretical view is correct, we have to determine by future studies. In our Harvard laboratory we have now proceeded from such preparatory mass experiments to subtle investigations on a small number of persons well trained in psychological self-observation with whom the conditions of the experiment can be varied in many directions.[39]