disposal for scientific analysis, but also shows that _an action, even in its simplest form, will vary with every shift of emphasis in the suggestion_ (p. 213) _which calls it forth_. Let us look, now, at the =reaction times=, and see if they can be turned to scientific account. So many experiments have been made that we know the average times of reaction, both sensory and motor, to light, sound and touch; and we also know what their average constancy or regularity will be, if the reactor keeps his attitude to the experiments unchanged. The times themselves, and the numerical statement of their constancy, may therefore be used as indexes to the type of reaction, sensory or motor, and to the stability or instability of the reactor’s attitude. _They embody, as if in short-hand, the results of oft-repeated observation_, and they may henceforth take the place of direct psychological observation when we are asked to decide on the type of reaction or the reliability of the reactor. The psychological observation must, however, come first; we cannot take the reaction-times of children or South Sea Islanders, and at once put them down as sensory or motor or mixed; we must know what the reactors were trying to do, how they understood the instructions given them. § 57. =The Degeneration of Action: From Impulsive to Reflex.=—We have now to trace the course of impulsive action, downward to automatic, and upward to deliberative action. If we start out on the downward path, we note that impulsive action by frequent repetition degenerates, first, to what is called =sensorimotor= or =ideomotor action=: sensorimotor, if the object is still _perceived_, as it is in the impulsive action proper (p. 235), and ideomotor, if the perception is replaced by an _idea_ of object. Here the predetermination is a nervous set without any mental correlates; the intention to move has dropped away; and the idea of result is, so to say, incorporated in the perception or idea of object; so that movement follows at once upon this perception or idea. When we sit down at table, for instance, we take up our knife _as_ a thing to cut food with; and when we are dressing, we close our fingers round a button _as_ a thing to fasten a garment with; the movements that we make are predetermined, but not premeditated; the actions are sensorimotor. When, again, it occurs to us, in the midst of our reading, that the mail must have arrived, we ideate the packet of letters _as_ something to be fetched from the mail-box; and when, as we watch the shower, it occurs to us that the cellar hatchway is open, we ideate the hatchway _as_ something to be closed; we act without further thought, and the actions are ideomotor.