Erection Research

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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  Yet, in his own 1949 edition, Dickinson continued this tradition by using an unpublished and undocumented analysis.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...." 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.