"I found that the reaction-time for impressions on the skin with electric stimulus is less than for true touch-sensations, as the following averages show:
Average. Average Variation Sound 0.167 sec. 0.0221 sec. Light 0.222 sec. 0.0219 sec. Electric skin-sensation 0.201 sec. 0.0115 sec. Touch-sensations 0.213 sec. 0.0134 sec. "I here bring together the averages which have been obtained by some other observers:
Hirsch. Hankel. Exner. Sound 0.149 0.1505 0.1360 Light 0.200 0.2246 0.1506 Skin-sensation 0.182 0.1546 0.1337"[124]
| Average. | Average Variation | |
| Sound | 0.167 sec. | 0.0221 sec. |
| Light | 0.222 sec. | 0.0219 sec. |
| Electric skin-sensation | 0.201 sec. | 0.0115 sec. |
| Touch-sensations | 0.213 sec. | 0.0134 sec. |
| Hirsch. | Hankel. | Exner. | |
| Sound | 0.149 | 0.1505 | 0.1360 |
| Light | 0.200 | 0.2246 | 0.1506 |
| Skin-sensation | 0.182 | 0.1546 | 0.1337"[124] |
Thermic reactions have been lately measured by A. Goldscheider and by Vintschgau (1887), who find them slower than reactions from touch. That from heat especially is very slow, more so than from cold, the differences (according to Goldscheider) depending on the nerve-terminations in the skin.
Gustatory reactions were measured by Vintschgau. They differed according to the substances used, running up to half a second as a maximum when identification took place. The mere perception of the presence of the substance on the tongue varied from 0''.159 to 0''.219 (Pflüger's Archiv, xiv, 529).
Olfactory reactions have been studied by Vintschgau, Buccola, and Beaunis. They are slow, averaging about half a second (cf. Beaunis, Recherches exp. sur l'Activité Cérébrale, 1884, p. 49 ff.).
It will be observed that sound is more promptly reacted on than either sight or touch. Taste and smell are slower than either. One individual, who reacted to touch upon the tip of the tongue in 0''.125, took 0''.993 to react upon the taste of quinine applied to the same spot. In another, upon the base of the tongue, the reaction to touch being 0''.141, that to sugar was 0''.552 (Vintschgau, quoted by Buccola, p. 103). Buccola found the reaction to odors to vary from 0''.334 to 0''.681, according to the perfume used and the individual.
The intensity of the signal makes a difference. The intenser the stimulus the shorter the time. Herzen (Grundlinien einer allgem. Psychophysiologie, p. 101) compared the reaction from a corn on the toe with that from the skin of the hand of the same subject. The two places were stimulated simultaneously, and the subject tried to react simultaneously with both hand and foot, but the foot always went quickest. When the sound skin of the foot was touched instead of the corn, it was the hand which always reacted first. Wundt tries to show that when the signal is made barely perceptible, the time is probably the same in all the senses, namely, about 0.332'' (Physiol. Psych., 2d ed., ii, 224).
Where the signal is of touch, the place to which it is applied makes a difference in the resultant reaction-time. G. S. Hall and V. Kries found (Archiv f. Anat. u. Physiol., 1879) that when the finger-tip was the place the reaction was shorter than when the middle of the upper arm was used, in spite of the greater length of nerve-trunk to be traversed in the latter case. This discovery invalidates the measurements of the rapidity of transmission of the current in human nerves, for they are all based on the method of comparing reaction-times from places near the root and near the extremity of a limb. The same observers found that signals seen by the periphery of the retina gave longer times than the same signals seen by direct vision.
The season makes a difference, the time being some hundredths of a second shorter on cold winter days (Vintschgau apud Exner, Hermann's Hdbh., p. 270).