Each subject in the photo sample was asked to complete a questionnaire
and received an invitation to have a follow-up documentary erection
photograph made. The black and white 35mm photos were taken
with the subject standing in profile view at a standardized distance,
with standardized lighting, and with a background containing an
angle grid and measurement scale immediately behind the erection.
A front view photo was taken without the background grid or measurement
scale. The background grid provided an estimate of the photo
erection angle, but the final determination of photo angle was made
by placing an angle-ruled plastic overlay on the developed and enlarged
In contrast to the questionnaire and photo techniques, the measures
for the Kinsey subjects were collected through a standardized face
to face interview (and supplemented with self-measurement for length
as described earlier). The following Kinsey variables (their
labels) were reanalyzed as a part of the present study:
The 3 variables immediately above are herein labeled shape, angle,
and length for brevity and consistency between samples. The
same variables, differently collected, were analyzed for the Kinsey
subjects and the photo subjects.
Age at time of interview
Curvature of penis
Angle of penile erection
Measured length of erect penis.
Shape in the Kinsey interviews was recorded in a 3x3 category system
consisting of 3 variations of shape when viewed from the side (curved
up, straight, curved down) and 3 when viewed from above from the
subject's point of view (curved left, straight, curved right).
The 9 resulting categories were retained for the present research
except that the labels for the side-view categories, curved up and
curved down, were changed in this report to u-curve and n-curve
respectively. This change was made because we felt the words
"up" and "down" were likely to elicit in the reader associations
related to the angle rather than to the curve of the erection.
Shape in the new data of the present research was determined from
drawings the respondent made on the questionnaire, from an answer
to a multiple choice question, and from photographic evidence.
Values analyzed on shape (a categorical variable) were the category
of agreement or best evidence.
Angle in the Kinsey interviews referred to the angle of the erection
from the body when the man was standing. The self-report of
the subject was recorded in 30º increments, with one major
exception. The horizontal position was reserved as a separate
category and covered only 10º. The two lowest 30º
segments were combined in the Kinsey Institute data summary, presumably because
the research team found so few erections reported in this range.
Figure 1 (imagine a man standing in profile with the front of his
body against the flat side of the figure) illustrates the resulting
Kinsey angle categories. In the present research we did not
constrain the reporting of angles to predetermined categories but
allowed each subject to draw the angle of his erection on a diagram
of a clock face which contained the hour numbers from 12 to 6 o'clock.
Since clock hours are 30º apart, this made for relatively easy
conversion to the Kinsey categories.
Figure 1. Degree Intervals
Used in the Kinsey Research
To be included in the photo sample, the self-reported (questionnaire)
angle of erection and the verified (photo) angle of erection had
to agree within 30º. Of 99 subjects who volunteered to
be photographed, 18 did not get fully erect and thus did not meet
this questionnaire-photo angle agreement criterion. This left
an active sample of 81. The 18 whose questionnaire and photo
data did not agree, were about 9 years older (mean age = 49.4 years)
than those with agreeing data. They reported an average erection
length (5.9") that was close to and slightly under the mean for
the total sample. However, being older, lower than average
angles might have been expectedbut the opposite was reported
on the questionnaires. In fact, the questionnaire angles of
these eliminated subjects were reported to be 22.4º higher,
on average, than the documented angles of the 81 subjects (mean
age = 40.4 years) who met the criterion of agreement and 13.8º
higher than the average for the Kinsey census sample (mean age =
39.8 years). The combination of being older, reporting higher
than average angles, and yet not obtaining a full erection for documentation,
suggests some degree of internal conflict that was not compatible
with the present research. It was probably inevitable and
appropriate that these candidates were screened out of the active
Length was measured to the nearest ¼ inch at home by the
Kinsey subjects and the results mailed to the researcher.
Measurements were on file for only 3,081 of the 9,865 subjects reviewed,
posing the unanswerable question of whether those who measured and
those who did not were systematically different on this variable.
Kinsey subjects also estimated their erection length during the
interview, but this estimate was not used in the present research.
For length data, respondents in the photo sample entered a dimension
in inches or centimeters on the questionnaire, using any fractions
they wished and indicating whether this was an estimate or a careful
measurement. Centimeter values were converted later to inches.
For the photo subjects, the values used for analysis of angle and
length consisted of the mean of the questionnaire and the photo
valuesexcept in the 26 instances when the photo value was
higher (in degrees) or longer (in inches), and then the photo value
was taken alone. Mean values were used because we reasoned
that self report would tend to over estimate and photography had
the potential to under estimate lengths and angles.
A substudy on length was conducted in which the researcher made
a direct measurement using a centimeter tape on 12 of the subjects
in the photo sample. In 4 cases the typical study measure
(questionnaire + photo averaged) was longer, by an average of 0.2
in. In 8 cases the centimeter tape measurement was longer,
by an average of 0.1 in. As a validity check on the present
study's measurement methodology, this small exercise suggests that
the questionnaire/photo method gives values that are within ±0.15
in. of a more traditional direct measurement procedure. Pomeroy
has been quoted as saying that were a researcher to be present to
measure a man's erection, the man would probably lose at least part
of it because of the researcher's presence.8 This
may have been a factor affecting the present data collection.
However, in our study, the 18% of subjects not meeting the questionnaire/photo
agreement criterion for inclusion, did not appear to lose part of
their erection, but rather did not fully acquire it in the first
place. Each subject in this study determined when he had an
optimal erection and if he were ready for photography or measurementwhich
required only a matter of seconds. This worked for the majority
(81%), for whom any reduction in length or angle from nerves or
from waiting was probably no more than the expected error of measurement.