In one respect, this historical severance of the reaction experiment from the special psychology of action has been of scientific advantage; it has left experimenters free to employ the reaction method in any connection in which it promised to be of service. _The technique of the reaction experiment has, in fact, proved useful in many investigations, in which the psychology of action is not involved._ Thus, we may measure the time required for response at different levels of _attention_, the time required (under various circumstances) for _recognition_, the time required for the _discrimination_ of sensations whose stimuli are more or less alike, and so on. There are a great many experiments into which this feature of time-measurement may be introduced; and when they have been often repeated, and standard times have been determined, the times themselves and the numerical statement of their constancy become psychologically significant (p. 242); they indicate, in a sort of short-hand way, what the observer has done and how uniformly he has done it. One of the most valuable extensions of the reaction experiment, from the practical point of view, is the _association reaction_; words are shown or called out to the observer, who replies in every case by the first word that comes into his mind. This experiment may be performed with abnormal as well as with normal reactors, and the results are of importance to the alienist. It has also been employed with a view to the detection of crime: a series of words, some of which bear upon the circumstances of the crime, is presented to the supposedly guilty person, and the time of his response to the critical words is taken as an indication of his guilt or innocence. Under laboratory conditions, with ‘crimes’ invented for the sake of the experiment, some rather surprising results have been obtained; but there have also been flat failures; and no one can yet say positively whether the association reaction will have its place in the legal procedure of the future. All these word-reactions move in the realm of meanings, which are the practically important things; there is no reason, however, why experiments of the kind described on p. 161 should not be accompanied by time-measurements. We have already suggested that moods might be timed (p. 227); and it is possible to measure the time required for the arousal of a sense-feeling, as well as to note its duration. On the whole, therefore, the reaction experiment or, as we may now term it, the =reaction method= should play an even larger part in the experimental psychology of the future than it has played in the past.