Harvard Psychological Studies, Volume 1: Containing Sixteen Experimental Investigations from the Harvard Psychological Laboratory.
Science
Harvard Psychological Studies, Volume 1: Containing Sixteen Experimental Investigations from the Harvard Psychological Laboratory.
Psychology, Experimental
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.
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