Review
of Relevant Literature
The first book in the USA that
attempted to be broadly descriptive of the penile erection was Human
Sex Anatomy, a Topographical Hand Atlas,1 published in
1933 and revised in 1949. In reading this book one can see that
the author, Dickinson, ardently wanted to present a fuller and more
accurate description than he was able. In his first edition
he lamented that "Elaborate search of medical and other literature
has brought to light no published series of measurements of the erect
penis..."1, and added "I know of no data based on studies
on the living that would enable one to depict an erection in its relation
to the body of a man...."1 He regretted that every
writer of the late 1800s and early 1900s who published average erection
dimensions, failed to give any scientific description of their data
or their data source. Yet, in his own 1949 edition, Dickinson
continued this tradition by using an unpublished and undocumented
analysis.
The erection research that used the most rigorous anthropometric
methods was a study of about 1,500 boys and young men from birth
to age 25 published between the two Dickinson editions by Schonfeld
and Beebe2 in 1943. In explaining their interest
in erections, these researchers made the canny statement, "The true
physiological length of the penis is its erect length...."2
Indeed, in the flaccid state, the penis has no single length, but
varies with the weather, bodily activity, and other environmental
influences. Nevertheless, Schonfeld and Beebe felt that it
was not feasible to make extensive observations of erections, and
settled for using the stretched penis as an erection surrogate.
Their method produced a distribution of length measures for the
mature group of 17 to 25 year old subjects that was, on average,
nearly 1.5 inches shorter than the Kinsey and photo data of the
present article.
The first "Kinsey Report" entitled Sexual Behavior in the Human
Male3 by Kinsey, Pomeroy, and Martin was published in
1948. While the Kinsey team was concerned principally with
sexual behavior, they collected from their male subjects basic descriptive
information on their erections. Much of the collected erection
data were not included in their report, but on the topic of erection
angle, they wrote:
In any age group there is considerable variation in the
angle at which the erect penis is carried on the standing male.
The average position, calculated from all ages, is very slightly
above the horizontal, but there are approximately 15 to 20 percent
of the cases where the angle is about 45º above the horizontal,
and 8 to 10 per cent of the males who carry the erect penis nearly
vertically, more or less tightly against the belly. The angle
of erection is, in general, higher in the early twenties, and lower
in more advanced ages.3
A profound strength of this study was its large data base, and
a weakness (for the study of erections) was the fact that the data
were self-reported by the subjects. In 1979, Gebhard and Johnson
authored a book that presented detailed tabulations of the data
of Kinsey and his colleagues, from not only the 5,300 interviews
that were the basis of the 1948 volume but from the "basic sample"
of interviews that were collected between 1939 and 1963.4
This book also described the Kinsey data collection methods.
For example, data on angle were collected by asking the subject,
"If you were standing up and you had an erection, at what angle
would the penis stick out from the body? Would it be like this?
Or this? etc." The interviewer would demonstrate a series
of angles using a vertical finger to represent the body and a finger
or pen to represent the penis.4
A similar question and procedure was used to ask about penile shape
(curvature or straightness). But to get a measured length
of the erect penis, "Respondents were given cards to fill out and
return in preaddressed stamped envelopes, and were instructed to
measure on the top surface from belly to tip of penis."4
In 1988 Jamison and Gebhard used the Kinsey Institute data for a
new analysis of the relationship between flaccid and erect penis
dimensions.5 They confirmed and extended findings
first reported by Masters and Johnson6 that there is
an inverse relationship between the length of the flaccid penis
and its increase in size during erection. Thus, shorter penises
experience a greater percentage increase, and the resulting variability
of erect size is less than the variability of flaccid size.
Here, we present new analyses of the classic Kinsey data set and
compare them to analyses of a smaller data set collected in the
1990s by entirely different methods.
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