Typical of the results with all the animals are the following (Table 3) which were obtained with No. 1, a male. The figures in each case indicate the average of fifty reactions. Reënforcement and inhibition are expressed in terms of the tactual reaction, i. e., the auditory-tactual reaction is so many per cent greater (reënforcement) or less (inhibition) than the tactual. In the tables reënforcement is indicated by the + sign; inhibition by the - sign. In the last column of the table is given the number of reactions that were reënforced or inhibited. This was determined by comparing directly the reactions of each pair. Cases in which the two reactions were the same were distributed equally between the two classes: tactual reactions reënforced by auditory stimulus, and tactual reactions inhibited by auditory stimulus. Assuming that the auditory stimulus was without effect upon the tactual reaction, the number of reactions in these two classes would be approximately the same, hence all auditory-tactual reactions over half in a series, i. e., over twenty-five, which are greater than the corresponding tactual reactions, are reënforced reactions, and can be taken as a measure of the reënforcing influence of the auditory stimulus. In the same manner all reactions over half which show inhibition can be taken as a measure of the inhibitory value of the auditory stimulus.

As preliminary tests described in an earlier paper[155] furnished evidence of sex-differences, it is worth while to compare the results given by the males and females in these experiments with momentary auditory stimulation. For purposes of comparison I have presented in Table 4 the reënforcement-inhibition values given by the males and females for each interval. Column one contains the value of the auditory-tactual reaction in terms of the tactual reaction; column two, the number of reactions in excess of half which were reënforced or inhibited.

TABLE 3. FROG NO. 1. MOMENTARY AUDITORY STIMULUS, HAMMER BLOW. WEIGHT USUALLY 5 OR 10 GRAMS

Interval.Reaction to
Tactual Stim.		Reaction to
Auditory and
Tactual Stim.		Amount of
Reënforc'm't
or Inhibition.		Number of
reactions
Reënforced
or Inhibited.
0˝6.84mm.11.08mm.+62.0%+17.0
.1522.22 28.96 +30.3 +17.0
.2516.30 21.72 +33.3 +13.0
.3524.90 25.32 + 1.7 + 0.5
.4517.56 13.64 -22.3 -10.0
.6517.46 15.72 -10.0 - 6.0
.9031.26 31.48 + 0.7 + 0.5

TABLE 4. MOMENTARY AUDITORY STIMULUS, HAMMER BLOW

Males
Nos. 1 and 3.		Females
Nos. 2 and 4.
IntervalPer centum Diff.No. of Reacts. Per centum Diff.No. of Reacts.
0˝+82.5% (Reënf't)+17.5+58.0%+12.7
.15+58.1 +17.0+25.4 + 8.5
.25+32.3 +12.7+39.8 +12.7
.35+ 4.0 + 1.2- 9.7 - 3.2
.45-13.5(Inhibition)- 7.2-13.9 - 7.2
.65-12.5 - 6.2-11.8 - 7.2
.90- 0.7 - 1.5- 2.6 - 0.5

In these results two striking differences between the males and females appear: first, the reënforcement is not so great for the females as for the males; second, inhibition appears earlier and continues longer with the females than with the males. The average reënforcement with simultaneous stimuli is 82.5% for the males against 58.0% for the females. Inhibition begins to appear in case of the females when the interval between the stimuli is .25˝ to .35˝; in case of the males it appears between .35˝ and .45˝. Finally at .90˝ interval inhibition is slightly greater for the females.

Although the exact significance of these facts is unknown, it is not improbable that they are indicative of fundamentally important sex-differences in reaction to sound. The males among frogs are usually the vocalists, although in some species the females also croak. Moreover, in case of the green frog the tympanum of the male is much larger than that of the female. The results presented would seem to indicate that certain sounds stimulate the males to activity, whereas they inhibit activity in the females.

Graphically represented, the results of the momentary auditory stimulus experiments with frogs Nos. 1, 2, 3, and 4 are as follows: