(1) fatigue-lapses are less in magnitude than for the hands, because the head-movement can be only a fraction of the forearm-movement;
(2) mean errors increase and constant errors decrease with speed-rise;
(3) similarity of individual head-forward and head-backward curves is suggestive, taken with the fact that no typical form of curve is to be found;
(4) head-backward constant errors are greater and less regular in all cases, suggesting that the eyes, in head-forward records, by getting spatial relations, are more efficient.
For lines 1 cm. long:
Average of six subjects:
For mean errors note:
(1) the head-backward records are less regular than the head-forward ones, and rise a little with speed-increase, showing visual assistance for accuracy or better muscular control for the forward movements or both;
(2) the constant errors show shortening of ruled lines at high speeds a little more marked for the head-forward results;