<< Adolescence >>

While the sexual history of the human male thus begins in earliest infancy and develops continuously to its maximum activity somewhere between the middle teens and twenty years of age, the steady progress of the development is, among primates, accelerated in a period of growth which is known as adolescence — the period in which there is an increased rate of physical growth and the final development of reproductive function. Various physical developments are involved in this adolescent growth, and they do not all begin or reach their conclusion simultaneously. Consequently, there is no single point at which adolescence may be said to begin, or any point at which it may be said to stop, but from the onset of the first adolescent development to the completion of all adolescent development, the time involved for the average (median) female is something between three and four years.

During adolescence the young male rather suddenly acquires physical stature and adult conformation, and he begins to produce an ejaculate which contains mature sperm and which can, therefore, effect fertilization when in contact with the egg of a mature female. These are the most obvious and the biologically significant developments of the period; but the student of human sexual behavior is concerned with adolescence, and must consider its physical signs and stigmata, not because the physical developments are in themselves of prime importance, but because adolescence marks what is, in most individuals, a considerable break between the patterns of sexual activity of the pre-adolescent boy and the patterns of the older boy or adult. The sexual life of the younger boy is more or less a part of his other play; it is usually sporadic, and (under the restrictions imposed by our social structure) it may be without overt manifestation in a fair number of cases. The sexual life of the older male is, on the other hand, an end in itself, and (in spite of our social organization) in nearly all boys its overt manifestations become frequent and regular, soon after the onset of adolescence.

In a portion of the cases the pre-adolescent sexual activities have provided the introduction to adult activities: simple heterosexual play turns into more sophisticated petting; pre-adolescent attempts at intercourse lead to adult coitus; some of the pre-adolescent homosexual play leads into similar adult contacts. This is true in about 50 per cent of all male histories which include any pre-adolescent play (Table 29). In an equal number of the cases the pre-adolescent play ends well before or with the onset of adolescence, and adolescent and more adult sexual activities must start from new points, newly won social acquirements, newly learned techniques of physical contact. In many cases the newly adolescent boy’s capacity to ejaculate, his newly acquired physical characters of other sorts, do something to him which brings child play to an end and leaves him awkward about making further socio-sexual contacts. The psychologic and social factors involved in this break between pre-adolescent sexuality and adult sexual activity are questions that will deserve considerable study by some qualified student. Those boys in whom child play does merge directly into adult activity are more often from less inhibited, lower social levels (Table 29).    

For all boys, the experiences of pre-adolescence, whether directly continued or not, must provide considerable conditioning which encourages or inhibits their sexual development in adolescent and in more adult years.

Adolescence is a period of time, and not a particular point in the life of the growing boy. It involves a whole series of developmental changes, some of which come earlier, some later in the course of events. Individuals differ materially in the ages at which they experience the first of these events, and somewhat in the sequence in which the other transformations follow (Table 35, Figure 27).

Corresponding adolescent developments in the male usually do not begin until a year or two after adolescence has begun in the female, and they usually take four years or more to reach their conclusion. In consequence, as far as physical development is concerned, the girl begins to “mature” at an earlier age, and reaches complete maturity before the average boy. The average female in the available sample had begun to turn adolescent by twelve years and four months of age.
Other data comparing physical developments of males and females at adolescence are, for example, in: Stratz 1909:298. Biihler in Stern 1927:155-169. Havelock Ellis 1929:138-142. Boas 1932:310. Westbrook et al. 1934:43-44 (Chinese boys and girls). Shuttleworth 1938a: fig. 8; 1939. Greulich in Henry ed. 1944:10-15. Hooton 1946:235-254. Reynolds 1946:124. Shuttleworth 1951: figs. 14, 118-120.

Shortly after the end of the first decade, the female begins to develop physically at a faster rate than she had before, and acquires pubic hair, hair under the arms, more mature breasts, and a body form more nearly like that of an adult. During this period of development, she menstruates for the first time. It is during this period that her ovaries mature and, for the first time, begin to release eggs which are capable of being fertilized and developing into new individuals. First menstruation for the average female in the sample had come just as she was turning thirteen.

Among most boys, the physical changes of adolescence come on more or less abruptly, usually between the ages of 11 and 14, and in that period their sexual activities are suddenly stepped up until, within another few years, most of them reach the maximum rate of their whole lives. Among most females, as the data show, sexual development comes on more gradually than in the male, is often spread over a longer period of time, and does not reach its peak until a good many years after the boy is sexually mature.

Exact studies of adolescent development should, of course, be based upon the direct examination and measurement of developing children, and our own data, based upon the recall of adults, cannot be as certain; but the average ages at each stage of development, calculated from our records, agree quite closely with those from the observational studies.

Chiefly within the past decade, several studies based on physical examinations of boys and girls have given precise information on the variation and average ages involved in the developmental changes of adolescence. Some of the studies (Baldwin 1916, Crampton 1908, 1944, Dimock 1937, Kubitschek 1932, Schonfeld 1943) have been cross-sectional, based on examinations of numbers of children of each age group; some, utilizing a longitudinal approach, have involved the more exact task of following the development of individual cases over a period of successive years (Boas 1932, Dearborn and Rothney 1941, Greulich et al. 1938, Jones 1944, Meredith 1935, 1939, Shuttleworth 1937, 1939). The latter, however, are not always the more fruitful studies, for such observations are tedious, and long-time contacts so often fail that only a few subjects can be followed through to conclusion.

Table 15. Comparisons of data obtained in four studies on pubic hair development
AGE Percent of Boys Beginning Pubic Hair Development
Crampton
1908		Dimock
1937		Schonfeld
1943		 Present
Study
% Cumu-
lated
%		 % Cumu-
lated
%		 % Cumu-
lated
%		 % Cumu-
lated
%
9-10             0.2 0.2
10-11     2.0 2.0     2.0 2.2
11-12 7.0 7.0 15.0 17.0 12.0 12.0 7.7 9.9
12-13 24.0 31.0 21.0 38.0 30.0 42.0 25.5 35.4
13-14 28.0 59.0 22.0 60.0 25.0 67.0 33.5 68.9
14-15 25.0 84.0 27.0 87.0 12.0 79.0 22.8 91.7
15-16 11.0 95.0 11.0 98.0 19.0 98.0 5.5 97.2
16-17 4.0 99.0 2.0 100.0 1.0 99.0 2.0 99.2
17-18 1.0 100.0     1.0 100.0 0.7 99.9
18-19              99.9
19-20              99.9
20-21             0.1 100.0
Cases 3835 1406 1475 2511
Mean 13.44 ± 1.51 13.08   13.45 ± 0.03
Median     13.17 13.43

The data from the Crampton, Dimock, and Schonfeld studies
were based upon physical examinations of young boys.
The present study has been dependent upon the memory of older persons
recalling their adolescent experiences.

Figure 15. Comparison of memory with observational data

Record for age of onset of growth of pubic hair.
The Crampton, Dimock, and Schonfeld studies based upon physical examinations of boys.
The present study based on memory of older persons recalling adolescent experience.
The studies which are based on direct physical examinations may be accepted as more accurate than our own, for we have relied for the most part on the memory of persons who were removed by various and sometimes long periods of years from the events which they were recalling; but it is interesting to find that our records give averages and total curves which are not significantly different from the data in the observational studies (Table 15, Figure 15). According to the memory of our subjects, physical changes in the adolescent boy usually proceed as follows: beginning of development of pubic hair, first ejaculation, voice change, initiation of rapid growth in height, and, after some lapse of time, completion of growth in height (Table 35, Figure 27). Similar data have been previously published from our laboratory (Ramsey 1943a) for a small sample of 291 younger males who were in or near the beginning of adolescence at the time of the study.

Our present, larger sample gives curves that are in most respects in close agreement with the Ramsey series; but his records show voice change beginning sooner after the onset of pubic hair growth and before the first ejaculation (also see Jerome 1937, Curry 1940, Pedrey 1945). The Ramsey data indicate that “breast knots,” or subareolar nodes which are homologous to those which regularly occur in the female, are found in at least one-third of these boys between the ages of 12 to 14 (Jung and Shafton 1935, Ramsey 1943). Physical examinations (Meredith 1935, 1939) on limited and selected series of males have shown that sudden body growth may begin nearer the time of pubic hair development than our older subjects recall. There are many individual differences in the sequence of events.

Tables 35, 19f. Adolescent physical development in the male and the female
Adolescent Physical Development
 Beginning and Cumulated Percents
AGE Pubic
Hair		 First
Ejaculation		 Menstruation Orgasm from
Any Source		 Voice
Change		 Body/Penis
Growth		 Breast
Development		 Completion
of Growth		 AGE
Begin.
%		 Cumul.
% 		Begin.
%		 Cumul.
% 		Begin.
%		 Cumul.
% 		Begin.
%		 Cumul.
% 		Begin.
%		 Cumul.
% 		Begin.
%		 Cumul.
% 		Begin.
%		 Cumul.
% 		Begin.
%		 Cumul.
% 		Begin.
%		 Cumul.
% 		Begin.
%		 Cumul.
%
Boys Girls Boys Girls Girls Boys Boys Girls Boys Girls
8-9         0.1 0.1             0.1 0.1             8-9
9-10 0.2 0.2 3 3 0.2 0.3 1 1 6 8     0.0 0.1 3 3         9-10
10-11 2.0 2.2 13 16 1.8 2.1 3 4     0.6 0.6 3.0 3.1 11 14 0.1 0.1     10-11
11-12 7.7 9.9 24 40 6.1 8.2 17 21 5 13 2.9 3.5 3.8 6.9 23 37 0.2 0.3 1 1 11-12
12-13 25.5 35.4 32 72 19.5 27.7 29 50     14.0 17.5 14.3 21.2 30 67 1.3 1.6 6 7 12-13
13-14 33.5 68.9 19 91 29.2 56.9 29 79     26.4 43.9 19.4 40.6 20 87 3.4 5.0 12 19 13-14
14-15 22.8 91.7 7 98 25.1 82.0 13 92 10 23 26.0 69.9 22.7 63.3 8 95 8.2 13.2 18 37 14-15
15-16 5.5 97.2 2 100 10.2 92.2 5 97     14.3 84.2 15.9 79.2 3 98 11.5 24.7 15 52 15-16
16-17 2.0 99.2     4.2 96.4 2 99     9.1 93.3 11.4 90.6 1 99 18.6 43.3 20 72 16-17
17-18 0.7 99.9     1.8 98.2 1 100     3.3 96.6 6.4 97.0 1 100 17.1 60.4 10 82 17-18
18-19   99.9     0.8 99.0         1.6 98.2 2.3 99.3     17.9 78.3 11 93 18-19
19-20   99.9     0.4 99.4     30 53 0.7 98.9 0.5 99.8     8.4 86.7 3 96 19-20
20-21 0.1 100.0     0.1 99.5         0.4 99.3 0.2 100.0     7.5 94.2 2 98 20-21
21-22         0.1 99.7         0.3 99.6         3.1 97.3 1 99 21-22
22-23         0.1 99.8         0.3 99.9         1.8 99.1 1 100 22-23
23-24         0.1 99.9           99.9         0.4 99.5     23-24
24-25         0.1 100.0         0.1 100.0         0.2 99.7     24-25
25-26                 24 77             0.2 100.0     25-26
Cases 2511 3850 3573 5770 5873 2279 1355 5081 2621 1038 Cases
Mean Age 13.45 12.3 13.88 13.1 21.2 14.44 14.49 12.5 17.47 16.0 Mean Age
Median Age 13.43 12.3 13.77 13.0 20.0 14.23 14.42 12.4 17.40 15.9 Median Age

Ages shown (e.g., 8-9) include the lower limit (e.g., 8), and extend to, but do not include, the upper limit (e.g., 9).
In each column, there may be cases lying beyond the age shown at the hundred per cent mark,
but such extreme cases total less than 0.5 per cent in any column, and consequently would not affect the percentages shown without decimal places.

It has been customary, both in general thinking and in technical studies, to consider that adolescence in the female begins at the time of first menstruation (barring any unusual disturbance of normal menstrual development). This is an error, and for several reasons an unfortunate error; for considerable physical growth which should be recognized as adolescent usually precedes the occurrence of the first menstruation. Most of the females in our sample reported the appearance of pubic hair as the first of the adolescent developments. Some of the females reported pubic hair development at ages as young as 8, but others did not recall that pubic hair had developed until the age of 18 (Table 19f, Figure 7f). For the median female in the sample, the hair had begun developing by 12.3 years of age.
Observational studies on the average ages at first appearance of the pubic hair in females are: Marro 1922:31 (at 13 to 14 years). Priesel and Wagner 1930:337. Pryor 1936:60. Reynolds 1946:122 (at age 11.2). Reynolds and Wines 1949:94 (at age 11).

Almost simultaneously with the appearance of pubic hair, breast development became noticeable. The observational studies show that the very first signs of breast development may actually precede the appearance of the pubic hair. Among the females in our sample there were some who recalled such development by the age of 8, and some who did not recall breast development until the age of 25 (Table 19f, Figure 7f). The median age of breast development was 12.4 years for the females in the sample.
Observational studies giving average ages at beginning of breast development in females include: Marro 1922:31. Priesel and Wagner 1930:342-345. Pryor 1936:61. Reynolds 1946:122 (at 10.7 years). Reynolds and Wines 1949:97. The following state that breast development is typically the first outward sign of adolescence: Stratz 1909:245. Moll 1909:33; 1912:36. Hoffman 1944:292. Hamblen 1945:117.

Only a few of the adult females in the sample were able to recall the age at which a marked increase in the rate of growth had first begun. It is difficult to notice the onset of a process which is as continuous as this increase in rate of growth during adolescence. A much larger number of the females in the sample thought they could recall the ages at which they had completed their development in height. These ages ranged from 9 to 25 years, but for the median female growth seemed to have been completed by 15.S years of age (Table 19f, Figure 7f).
There are a number of observational studies on increases in height and weight at adolescence, including, for instance: Stratz 1909:317. Boas 1932. Pryor 1936:56-59. Barker and Stone 1936. Stone and Barker 1937. Shuttleworth 1937, 1938b, 1951: figs. 118-120. Greulich in Henry ed. 1944:20. Reynolds 1946:125. Dennis in Carmichael 1946:638-640 (a good survey, beginning with Bowditch 1891). Reynolds and Wines 1949:105-109.

Figures 27, 7f, 8f. Cumulated percents: adolescent physical development in the male and the female.

Data for males in more bright colors.
Comparing female and male: onset of adolescence and sexual response.
Taking appearance of pubic hair as first adolescent development, and orgasm or ejaculation as specific evidence of erotic response.
For males are given onsets of: pubic hair, ejaculation, voice change, body/penis growth, and completion of growth.
For females are given onsets of: pubic hair, breast development, menstruation, orgasm from any source, and completion of growth.


The published studies of younger boys almost completely lack data on the most significant of all adolescent developments, the occurrence of the first ejaculation. There have been several attempts to secure information by indirect methods, including a technique of examining for sperm in early morning samples of urine (Baldwin 1928). These methods will not soon supply any quantity of data; and the only other sources of information on this point have been the records obtained from the recall of subjects in the previously published case history studies. This material is now augmented by a considerable record based on the memory of persons who have contributed to the present study, and on an important body of data from certain of our subjects who have observed first ejaculation in a list of several hundred boys.

The earliest ejaculation remembered by any of our apparently normal males was at 8 (three males). We have the history of one unusual boy (a Negro, interviewed when he was 12) who fixed 6 as his age at first ejaculation. The boy had been diagnosed by the clinician as “idiopathically precocious in development.” In the literature (e.g., Ford and Guild 1937, Young 1937, Weinberger and Grant 1941) there are clinical cases for still younger ages, most of them involving endocrine pathologies. Pubic hair has been recorded for one year of age and non-motile sperm in urine after prostate massage at four and a half years. Eight, however, is the earliest age of first ejaculation known for apparently normal males.

Except for the 6 cases of life-long ejaculatory impotence referred to earlier in the present chapter, the latest ages of first ejaculation reliably recorded in the histories are 21 for two apparently healthy males, 24 for a religiously inhibited individual, and 22 and after 24 for two males with hormonal deficiencies. The spread between the youngest and the oldest non-endocrine case is 16 years. A variety of educational and social problems arise out of these differences between chronologic and sexual age. For instance, an occasional boy in third or fourth grade is sexually as mature as an occasional senior in college (Table 36, Figure 28).

Table 36. Adolescent developments
School
Grade		 No. of Boys
Beginning
Adolescence		 % of Boys
Beginning
Adolescence		 Cumulated %
Adolescent
at End of Grade
1 6 0.16 0.16
2 14 0.38 0.54
3 42 1.13 1.67
4 82 2.20 3.87
5 180 4.83 8.70
6 409 10.96 19.66
7 667 17.88 37.54
8 959 25.71 63.25
9 863 23.14 86.39
10 376 10.08 96.47
11 96 2.57 99.04
12 24 0.64 99.68
13 11 0.29 99.97
14 1 0.03 100.00
Total 3730 100.00 100.00
Mean grade at onset of adolescence: 8.33 0.028
Median grade at onset of adolescence: 8.49

Most of the boys reaching adolescence in the lowest grades
are retarded individuals of more advanced age than the average in the grade.

 

Figure 28. Percent of adolescent boys in each school grade.

In spite of this spread in the population as a whole, the record shows (Table 35, Figure 27) that about 90 per cent of the males ejaculate for the first time between the ages of 11 and 15 (inclusive). This is an age range of 5 years. At the end of the seventh grade in school, about a third (37.5%) of the boys are adolescent; by the end of the tenth grade, nearly all of them (96.5%) are so (Table 36, Figure 28). The average boy turns adolescent in the eighth grade (a mean grade of 8.33).

The mean age of first orgasm resulting in ejaculation is 13 years, 10 1/2 months (13.88 years). On this point, the male data are in striking contrast with preliminary calculations on the female. By 15 years of age, 92 per cent of the males have had orgasm, but at that same age less than a quarter of the females have had such experience; and the female population is 29 years old before it includes as high a percentage of experienced individuals as is to be found in the male curve at 15. Precise data on the female must await the publication of a later volume.

In the male the age of first ejaculation varies by nearly a year between different educational (social) levels: the mean is 14.58 for boys who never go beyond eighth grade in school, 13.97 for boys who go into high school but not beyond, and 13.71 for boys who will go to college (Table 37). The differences are probably the outcome of nutritional inequalities at different social levels, and they are in line with similar differences in mean ages of females at menarche, where nutrition is usually considered a prime factor effecting variation.

Table 37. Ages at onset of adolescence

Ages at Onset of Adolescence

AGE

Educational Level
0-8

Educational Level
9-12

Educational Level
13+

Cases

% of
Popula-
tion

Cumu-
lated
Per-
cent

Cases

% of
Popula-
tion

Cumu-
lated
Per-
cent

Cases

% of
Popula-
tion

Cumu-
lated
Per-
cent

8-9

1

0.2

0.2

2

0.1

0.1

9-10

1

0.1

0.1

2

0.3

0.5

7

0.3

0.4

10-11

7

0.9

1.0

11

1.8

2.3

70

2.5

2.9

11-12

22

2.9

3.9

32

5.2

7.5

221

7.8

10.7

12-13

104

13.6

17.5

123

19.9

27.4

707

25.1

35.8

13-14

185

24.1

41.6

189

30.5

57.9

980

34.8

70.6

14-15

275

35.8

77.4

205

33.0

90.9

647

23.0

93.6

15-16

137

17.8

95.2

39

6.3

97.2

126

4.5

98.1

16-17

31

4.0

99.2

13

2.1

99.3

37

1.3

99.4

17-18

5

0.7

99.9

3

0.5

99.8

15

0.5

99.9

18-19

1

0.1

100.0

1

0.2

100.0

2

0.1

100.0

19-20

1

—

100.0

Total

768

100.0

619

100.0

2815

100.0

Mean

14.14 ± 0.044

13.67 ± 0.049

13.39 ± 0.023

Median

14.24 years

13.75 years

13.41 years

Age

Total Sample Population

Corrected for U. S. Population

Cases

% of
Population

Cumulated
Percent

% of
Population

Cumulated
Percent

8

3

0.1

0.1

0.1

0.1

9

10

0.2

0.3

0.2

0.4

10

93

2.0

2.3

1.6

2.0

11

304

6.6

8.9

4.9

6.9

12

1035

22.5

31.4

18.7

25.6

13

1507

32.8

64.2

29.1

54.7

14

1209

26.3

90.5

32.4

87.1

15

316

6.9

97.4

9.6

96.7

16

85

1.9

99.3

2.6

99.3

17

23

0.5

99.8

0.6

99.9

18

4

0.1

99.9

0.2

100.0

19

1

0,1

100.0

—

100.0

Total

4590

100.0

100.0

Mean

13.55 ± 0.018

Median

13.56 years

  
Comparing development for three groups defined in accordance with the years of schooling ultimately attained:
 -- “Educ. level 0-8” are the males who never go beyond grade school.
-- “Educ. level 9-12” are the males who enter high school but never go beyond.
-- “Educ. level 13+” are the males who will ultimately go to college.
Figures for the U. S. population are based on the figures for the sample population corrected for the educational distribution shown in the U. S. Census for 1940.

Figure 29. Age at onset of adolescence, by three educational levels.
 Curve for total population, on the basis of the U. S. Correction, is shown in the blue line.

Since so many developments are involved, it is difficult to mark a single point at which an individual may be said to have begun adolescence. In the case of the male, it is not customary to attach that distinction to the very first appearance of any adolescent change, but to pay more attention to the time of first ejaculation, or to evidence that the boy would be capable of ejaculation if the proper opportunity were at hand. We have, to a large degree, followed this convention, in order that the calculations may be compared with other published figures. If the year of first ejaculation coincides with the year in which the pubic hair first appears, with the time of onset of growth in height, or with other developments, there is no question involved. If first ejaculation follows these other events by a year or more, the record must be examined to see whether there was overt sexual behavior which would have provided previous opportunity for orgasm, and the reliability of the record on the other adolescent characters must be checked. First ejaculation which is derived from nocturnal dreams usually occurs a year or more after the onset of other adolescent characters and after ejaculation would have been possible by other means, if circumstances had allowed. Taking these several things into account, “adolescent ages” have been assigned to each of the subjects in the present study, and the distribution is shown in Table 37, Figure 29. When computed thus the average age of onset of adolescence in the white male is about 13 years and 7 months.

Table 38. Sources of first ejaculation
Source Number of Adolescent
Males		 Percent of Population
Popu-
lat. in
Sample		 Educ.
Level
0-8		 Educ.
Level
9-12		 Educ.
Level
13+		 Popu-
lat. in
Sample		 Educ.
Level
0-8		 Educ.
Level
9-12		 Educ.
Level
13+		 Total
U. S.
Popu-
lation 1
No Ejaculation 14 4 2 3 0.4 0.6 0.4 0.1 0.42
Masturbation 2378 455 346 1293 66.2 68.2 70.1 62.2 68.39
Noct. Emiss. 798 47 58 654 22.2 7.1 11.7 31.4 13.11
Petting 13 2 2 9 0.4 0.3 0.4 0.4 0.37
Coitus 222 123 60 29 6.2 18.5 12.1 1.4 12.53
Homosexual 103 32 23 39 2.9 4.8 4.7 1.9 4.33
Animal Coitus 6 0 0 6 0.2 0.0 0.0 0.3 0.04
Spontaneous 54 3 3 48 1.5 0.5 0.6 2.3 0.81
Total 3588 666 494 2081 100.0 100.0 100.0 100.0 100.00
“Educ. level 0-8” are the males who never go beyond grade school.
“Educ. level 9-12” are the males who enter high school but never go beyond.
“Educ. level 13+” are the males who will ultimately go to college.

1 The final column shows percent involved
if each educational level were represented in the proportions shown in the 1940 Census.

Figure 30. Sources of first ejaculation

Calculated for total population corrected for U. S. Census distribution, and for boys
of the grade school (0-8), high school (9-12), and college (13+) levels.


For the U. S. population, the sources of first ejaculation (Table 38, Figure 30) are, in order of frequency, masturbation (in about two-thirds of the males), nocturnal emissions (in an eighth of the cases), heterosexual coitus (in one boy out of eight), and homosexual contacts (in one boy out of twenty), with spontaneous ejaculation, petting to climax, and intercourse with other animals as less frequent stimuli for the initial experience (cf. Rohleder 1921). There are considerable differences in first sources in different educational levels. The highest incidence of masturbation as the first source of ejaculation occurs among the boys who will leave school between the ninth and twelfth grades, the highest incidence of nocturnal emissions as the first source occurs among the boys who will subsequently go to college, and the highest incidence of heterosexual intercourse as the first source occurs among the boys who never get beyond the eighth grade in school.

While “spontaneous” ejaculation, meaning ejaculation without specific genital contact, is the first source of experience for only a small percentage of the boys (0.81%), the items which stimulate such response constitute an interesting list which includes non-sexual and more definitely sexual emotional situations, and a variety of circumstances which involve physical tension. In a number of cases (e.g., wrestling, prolonged sitting while reading a book) both physical tension and psychologic stimulation are probably involved. The list includes a number of the non-sexual sources of erotic stimulation listed earlier in this chapter, but the following tabulation shows items which are responsible for actual ejaculation among these early adolescent boys.
 

Sources of First Spontaneous Ejaculation
                              Chiefly Physical Stimulation
Sitting at desk
Sitting in classroom    
Lying still on floor    
Lying still in bed    
Urination    
At toilet    
General stimulation in bath    
Moving water in bath    
General stimulation with towel    
General skin irritation
Vibration of a boat		 Sliding on chair    
Sliding down a bannister
Tension in gymnastics
Chinning on bar
Climbing tree, pole or rope
    (A rather common source)
Wrestling with female
Wrestling with male
Riding an automobile
Tight clothing
                              Chiefly Emotional Stimulation
Day dreaming    
Reading a book    
Walking down a street    
In vaudeville    
In movies    
Kissed by female    
Watching petting    
Peeping at nude female    
Sex discussion at YMCA		 Milking a cow
When scared at night
When bicycle was stolen
A bell ringing
An exciting basketball game
Trying to finish an examination in
     school
Reciting in front of class
Injury in a car wreck

Beyond earliest adolescence, it is a rare male who ejaculates when no physical contact is involved. Many teen-age and even older males come to climax in heterosexual petting that may not involve genital contacts; but general body contact, or at least lip contact, is usually included in such situations. There are stray cases of males of college age ejaculating under the excitement of class recitation or examination, in airplanes during combat, and under other rare circumstances. There are two cases of older males who could reach climax by deliberate concentration of thought on erotic situations; but such spontaneous ejaculation is almost wholly confined to younger boys just entering adolescence.

After the initial experience in ejaculation, practically all males become regular in their sexual activity. This involves monthly, weekly, or even daily ejaculation, which occurs regularly from the time of the very first experience. Among approximately 4600 adolescent males, less than one per cent (about 35 cases) record a lapse of a year or more between their first experience and the adoption of a regular routine of sexual activity. This means that more than 99 per cent of the boys begin regular sexual lives immediately after the first ejaculation. In this respect, the male is again very different from the female, for there are many women who go for periods of time ranging from a year to ten or twenty years between their earlier experiences and the subsequent adoption of regularity in activity. The male, in the course of his life, may change the sources of his sexual outlet, and his frequencies may vary through the weeks and months, and over a span of years, but almost never is there a complete cessation of his activity until such time as old age finally stops all response.

For the female, the age of first menstruation had ranged from 9 to 25 years in the sample (Table 19f, Figure 7f). For the median female it had been 13.0 years.
Average ages of 13 years for first menstruation are found in such studies as: Baldwin 1921:191. Bingham 1922:543. Abernethy 1925:540. Boas 1932:309. Engle and Shelesnyak 1934:434. Glueck and Glueck 1934:425. Mazer and Israel 1946:66. Other data on age at first menstruation are in: Mills 1937:48-56. Greulich 1938:52-53. Shuttleworth 1938a: figs. 108-114. Ito 1942:333-345 (effect of race and climate). Greulich in Henry ed. 1944:28-29. Ashley Montagu 1946:83. Dennis in Carmichael 1946:634, 641-643 (comprehensive survey). Dickinson 1949: fig. 46a.

For the median female, there had been a lapse of 8.4 months between the onset of pubic hair and breast development, and the first menstruation. The first menstruation is such a specific event and, in many instances, such a dramatic event in the girl’s history, that its appearance is recalled more often than any other adolescent development. It is, therefore, quite natural that since the time of ancient Jewish law, menstruation should have been taken as the best single sign of sexual maturity in the female. Unfortunately, menstruation is a phenomenon which is affected by a larger number of factors, chiefly hormonal, than most of the other biologic developments at adolescence. In a few instances it may begin before there are any other adolescent developments. Not infrequently, however, it may be delayed for a considerable period of time, and in some instances for several years, after all of the other adolescent developments have been completed. It is customary today for parents to seek medical aid when first menstruation does not appear by the time the other adolescent developments are well under way; but among many of the older women in our histories, menstruation would have been a poor indicator of adolescent development.

It is popularly believed that the appearance of menstruation is an indication that a girl has become “sexually mature” enough to conceive and reproduce. On the basis of recent studies, it becomes clear, however, that the initial release of mature eggs from the ovaries is not always correlated with menstruation. There are known cases of fertile eggs and pregnancy occurring before menstruation had ever begun; and there is a considerable body of data indicating that the average female releases mature eggs only sporadically, if at all, during the first few years after she has begun to menstruate. This is the period of so-called adolescent sterility. It is probable that the sterility is not complete, and more probable that eggs are occasionally released in that period; but regular ovulation in each menstrual cycle probably does not begin in the average female until she is sixteen to eighteen years of age. Precise studies on this point are still to be made.
For original data on adolescent sterility and for bibliographies of other studies see: Hartman 1931 (first use of term, data on monkeys). Yerkes 1935:542 (chimpanzee). Mills and Ogle 1936 (sterile period shorter if menstruation starts later). Greulich 1938:54. Siegler 1944:17-19. Ashley Montagu 1946:57-141 (most extensive summary of data). Dennis in Carmichael 1946:645 (summary of data). Shuttleworth 1951: figs. 125, 126 (summary of data). Webster and Young 1951 (in male guinea pigs).

While these physical changes at adolescence are a fundamental part of the process by which the female becomes mature enough to reproduce, they seem to have little relation to the development of sexual responsiveness in the female. The steady increase in the accumulative incidence of erotic arousal and response to orgasm which we have seen in the pre-adolescent data continues into adolescence and for some years beyond. There is a slight but no marked upsurge in the incidence and frequency of arousal and orgasm during adolescence, but they do not reach their maximum development until the middle twenties or even thirties.

In the case of the male, there is a sudden upsurge in sexual activity which may begin a year or more before adolescence, and usually reaches its peak within a year or two after the onset of adolescence (Figure 8f). From that point the male’s sexual responses and overt activity begin to drop and continue to drop steadily into old age. These striking differences between female and male psychosexual development may depend upon basic hormonal differences between the sexes.

Because of the earlier appearance of adolescence in the female, and because of her more rapid physical development in that period, the opinion is generally held that the girl matures sexually more rapidly than the boy. Mature reproductive cells may appear in the average female before they appear in the average male, but the capacity to reproduce is not synonymous with the capacity to be aroused erotically and to respond to the point of orgasm. The irregular release of mature eggs from the ovaries during the years of adolescent sterility makes it uncertain whether the capacity for reproduction develops earlier in one sex than in the other, and in regard to sexual responsiveness the female matures much later than the male.
It has usually been stated that girls show an earlier (6 months to 2 years) heterosexual interest than boys; see, for instance, Campbell 1939:470. Sadler 1948:338. Waller 1951:150. Such studies, however, do not clearly distinguish social interests from erotic responses. For studies recognizing the later erotic development of the female, which we find in our data, see: Kisch 1907:173 (also cites Loewenfeld). Bühler in Stern 1927:155-169. Hamilton 1929:488 (5 out of 100 married females, but 54 out of 100 married males had ‘longed for coitus” by age 15). Gurewitsch and Grosser 1929:521 (an important body of data on 536 females and 2280 males; reports arousal among females beginning on an average of 1.1 to 1.4 years later). Havelock Ellis 1936 (1,2): 242-247 (generally recognizes later erotic development of female, cites literature beginning with Ovid). Pratt in Allen et al. 1939:1283 (complete response seldom possible for a woman before maturity).

We have found that the human female is born with the nervous equipment on which sexual responses depend, but we have found that only a portion of the females respond before the onset of adolescence. The acquirement of any full capacity for response depends upon the sort of sexual experience that the female has in pre-adolescence, adolescence, and the later years, and on the variety of social factors which may condition her psychologically.

>>