Robert M. Yerkes

Bahnung und Hemmung der Reactionen auf tactile Reize durch akustische Reize beim Frosche

I n h a l t s i i b e r s i c h t : seit~ I. Problem der Versuche . . . . . . . . . . . . . . . . . . . . . 207 II. Methode . . . . . . . . . . . . . . . . . . . . . . . . . . . . 208 III. Ergebnisse der Versuche . . . . . . . . . . . . . . . . . . . . 212 1. Vorversuche . . . . . . . . . . . . . . . . . . . . . . . . 212 2. Der Eintiuss momentaner akustischer Reize auf tactile Reactionen 213 3. Der Einfluss dauernder akustischer Reize auf tactile Reactionen. 222 IV. Verhhltniss zu friiheren Bearbeitungen der vorliegenden Probleme . 226 V. Discussion der Resultate . . . . . . . . . . . . . . . . . . . . . 232 u Ergebnisse . . . . . . . . . . . . . . . . . . . . . . . . . . 236

Bodily Electrical Potential Changes Associated with Ovulation and Early Pregnancy in the Chimpanzee.

Recently Burr and associates 1 discovered that ovulation in the rabbit is accompanied by large increases in electrical potential. Observations on women, using the apparatus and technique described by Burr, Lane, and Nims, 2 have been reported by Burr and Musselman. 3 Applications of the vacuum tube potentiometer have been reported also by Reboul, Friedgood, and Davis, 4 and by Rock, Reboul, and Wiggers. 5 The present preliminary report offers the results of an attempt to apply the Burr-Lane-Nims technique to the study of ovulation in the chimpanzee. A sexually mature chimpanzee (No. 4 in the laboratory series), with regular menstrual cycles, was trained to present the backs of her hands for the application of salt-bridge electrodes and to remain passive during the course of a series of potential difference measurements. Measurements were taken daily over a period of several weeks. The curve of Fig. 1 shows the potential measurements in millivolts through a normal sexual cycle (April 6 to May 6). Each voltage point represents the median of 10 or more determinations, with the exception of days 5,10, and 12. On these days there were 4, 2, and 4 observations respectively. Occasional refusal of the subject to coöperate or temporary difficulties with the apparatus account for the omission of data for certain days. The menstrual history of our subject and previous results of the controlled mating method 6 enabled us to predict that ovulation should occur in this subject on the 16th or 17th day. Accordingly, on days 16, 17, and 18 one or two additional series of observations were made. The sexual status of the subject is represented below the voltage curve. The line following the 4 days of menstruation represents the relative amount of genital swelling. The heavy portion of this line indicates the period of maximal swelling. General description of the sexual cycle of the chimpanzee has been given by Elder and Yerkes. 7 In contrast with the small variations in potential which appear from day to day, the median for the 17th day is higher than any of those before or after that date. The magnitude of this maximum value is not as great as might be expected, but it occurs at the time predicted, and also, if it is indeed a phenomenon associated with ovulation, stands in appropriate relationship to the beginning of detumescence. All of our isolated fertile matings fall within the last 6 days of maximal genital swelling. Fig. 2 presents similar data for the next cycle of the same female. A maximum value again appears on the 17th day, followed by another peak 4 days later. Ihis second rise m the curve is ot particular interest because of a subsequent diagnosis of pregnancy confirmed by a series of Friedman tests. Because pregnancy was not suspected at the time that the high readings were obtained on days 21-23, the apparatus was completely dismantled for checking, and a period of 22 days elapsed before it was reassembled and put into operation again. We are inclined to interpret the high potentials of the 17th day as concomitant with ovulation, while those of the 21st day may be correlated with fertilization and early pregnancy changes. These results indicate that the Burr-Lane-Nims technique may prove valuable for the early diagnosis of pregnancy as well as for the detection of ovulation in the chimpanzee.

Habit and its relations to the nervous system in the earthworm

This is a preliminary report of an investigation now in progress, the purpose of which is (a) to demonstrate whatever ability the earthworm may have to acquire habits of a certain order; (b) to discover the characteristics of any habits which appear; (c) to enumerate and evaluate the various external and internal influences on habit-formation; (d) to ascertain the degree of permanency of the habits and (e) to discover their relations to the anterior ganglia (brain). By means of a T-shaped maze constructed from plate glass, specimens of the manure worm, Allolobophora fetida, were tested. The maze was placed with the stem directed toward the light. Across one of the arms a piece of sandpaper was placed and, just beyond it, a pair of electrodes. The other arm was left open so that the worm might escape to an artificial burrow. The worms were driven into the T by light and the chief motive for escape therefrom was the tendency to avoid light. It was the purpose of the test to demonstrate (a) any ability which the manure worm may possess to acquire a direction habit and (b) to associate the tactual experience of contact with sandpaper with the electrical shock which regularly followed the tactual stimulus in case the worm continued to move forward after reaching the sandpaper. Trials were made in daily series varying in number from five to twenty. The five-trial series were found, on the whole, most satisfactory. Referring now exclusively to the results obtained for a single worm which has been under observation since October, 1911, the following data may be presented. (I) Allolobo@hora is capable of acquiring certain definite modes of reaction. (2) Modifications appear as the result of from twenty to one hundred experiences.

The relation of plasticity to sex and age in the dancing mouse

Plasticity or the modifiability of behavior in the dancer has been studied by measurement of the rate of habit formation. The habit of choosing a white box instead of a black box was established by means of systematic training, on the basis of the association of an electric shock with the latter. Each animal was subjected to ten tests daily until it chose correctly on three consecutive days. The habit was then considered perfect and the training ceased. We may speak of the number of tests necessary for the establishment of a perfect habit as the index of plasticity. The index, then, may be defined as the number of tests up to the point at which errors of choice ceased for at least three days. In order to discover the relation of sex and age to plasticity five pairs of mice were trained for each of the ages, one, four, and seven months. The investigation is unfinished, as older individuals are to be tested. In this table each index for the males and the females is the average for five individuals. In the last column the results for the sexes are combined. Sex differences which appear in the above table. 1. At the age of one month the males learn more quickly than do the females. The males require only 82 tests; the females require 106 for the establishing of a perfect habit. Consequently the index of plasticity for the one-month males is 82; that for the one-month females, 106. 2. At the age of four months the opposite is true. The females learn much more quickly than the males. As the table shows, the index for the males is 128; that for the females 106.

The senses and intelligence of the Chinese dancing mouse

For a few days during the first month of post-natal life the dancing mice which I have studied respond definitely to sounds, but neither direct nor indirect methods of testing auditory sensitiveness furnish any evidence of it in the adult. Brightness vision is fairly acute; color vision is poorly developed. I have some evidence of the discrimination of red and blue, and of red and green, but no evidence that blue and green can be distinguished. In visual discrimination the mice apparently depend upon brightness differences. The behavior of the dancing mouse is readily modifiable. Choice, by exclusion, of one of two objects which differ in brightness, with electrical stimulation in the case of a wrong choice, indicates that from 40 to 100 repetitions of an experience is necessary for the formation of a perfect habit. Such a modification of behavior lasts for from two to five weeks. Modifications of behavior occur more rapidly in the male than in the female. Individual differences in plasticity and in the permanency of modification are marked. There is little evidence of any form of imitative tendency in behavior.