Page:Philosophical Review Volume 2.djvu/116

102 filled intervals appear longer than empty intervals); Stevens, Nichols, F. Martius (rhythm); Paneth (alteration of reproduced times with magnitude of interval between apprehension and reproduction). (3) New experiments. (a) Method of right and wrong cases. — Sensible discrimination is largely dependent on the magnitude of the difference between normal-time and comparison-time. The lowest relative difference-limen obtained was $1⁄46$ (N = 400 σ, D = 13.3 σ; for D = 20 σ, the limen was $1⁄30$). The constant time-error is positive for times $$\ge \;$$ 600 σ. Very perfect practice is required. The results confirm the theory. (b) Method of reproduction. — The mean error does not measure sensible discrimination. Small times are not over-estimated, if the normal time and the interval between experiments are kept constant. That the time-error for a large time is negative (Vierordt) is due to the method. $$\S \;$$11. Further experimental facts confirm the theory. A strong limiting stimulus shortens the period: this is due to the secondary impression of surprise. An empty time, separated by an interval from an equal (normal) empty time, appears smaller (cf. Hall): this is also due to surprise. Biaural experiments, again, showed the influence of expectation. Whether the stimulus-limen is reduced in consequence of adaptation of the sensory attention, could not be determined. No respiration-uniformity (ct. Münsterberg) was discovered.

E. B. T.

The negative after-image of a colored object is not always of the complementary quality. In the writer's case, the normal dark blue image, produced by a yellow stimulus, became light green, under circumstances of physical and mental fatigue. He compares with this the "Abklingen" of solar after-images.

E. B. T.

This paper describes a research made in Ebbinghaus's laboratory at Berlin, to determine the effects of different disturbances upon reaction-time. The experiments covered the following cases: simple muscular reactions to an auditory stimulus, the attention being disturbed through the sense of hearing; auditory choice-reactions with auditory disturbance; muscular reactions to a visual stimulus with visual disturbance;