In the experiments in which the time was recorded, there was no disappearance of either image except where movements were made successively.  In these cases frequently the image which was awaiting its turn vanished until the first image was placed, a time varying from a quarter of a second to three or four seconds.  Occasionally the image already placed would vanish, while the other was en route; the subject’s attention in both these cases being centered exclusively on the image he desired to move.  This was especially the case when the distances to which the images were moved were great, as to the ends of the room or to ceiling and floor.  In other experiments, where, after the movements took place, the images were held for a short time, there were disappearances of one image or the other ranging from one quarter of a second to fifteen seconds, most of the absences, however, being under five seconds.  The absences were more numerous in the latter half of the five minutes covered by the experiment.  Occasionally a noise in the adjoining room or in the street made the images disappear.

The greater ease of vertical as compared with horizontal movements recalls an observation of Ladd,[3] in which the idioretinal light was willed into the shape of a cross.  Ladd says:  “The vertical bar of the cross seems much easier to produce and to hold steadily in the field.”  This present observation is also in accord with that described above in the case of movements of a single image.

   [3] Ladd, G.T.:  ‘Direct Control of the Retinal Field,’ PSYCH. 
   REV., 1894, L, pp. 351-355.

On several occasions G. reported that the crossing movement was the easiest, and that the return to the original places was not easier than the other movements.  In one experiment he reported the field at the center cloudy, so that it was a relief to get away from it.  G.’s time records on these occasions did not support his feeling with regard to the return to the original places, but they show that the crossing movements were, in two or three instances, quicker than the ‘left-and-right’ movement, and the impression of promptness thus made persisted to the end of the experiment.  The four movements in which both images moved uniformly were easier than the four in which movements in different directions were involved.

All the subjects were frequently conscious of eye movements, and more frequently conscious of a tendency to eye movement, which was, however, inhibited.  That the strain in the eyes was practically constant during all the movements away from the original places, seems evident from the unanimous reports of a sense of relaxing and relief in the eyes, attending the movement of returning to the original places.  The distance to which the images were moved was a powerful factor in producing this sense of strain.  When the two images were moved and held but a few inches apart there was no sense of strain and no conscious alternation of attention.  Practice increased greatly the distance at which the images could be held apart without conscious alternation of attention, but the strain of holding them apart and of inhibiting eye movement increased with the distance.