Hello again, Stan.
Thank you for a most interesting question.
The scientific and medical communities have devised a number of
different techniques for testing for the presence of erections in men.
These range from simple devices, such as test strips resembling
postage stamps (which are pasted to the penis, and which separate at
perforations if an erection occurs) to much more sophisticated devices
that can make a permanent, quantitative record of the size, strength
and duration of erections. Although not without its critics, the
Rigiscan device is emerging as the gold standard of such sophisticated
Why make such measurements? There are two primary reasons:
Research Behavioral scientists that study human sexual activity
(sometimes known as sexologists) may use an instrument like the
Rigiscan as an objective indicator of sexual arousal in men, measuring
physiological response to visual or other types of stimuli. Some of
the experimental questions I came across are actually pretty
interesting when experimental subjects are shown sexually explicit
images, what percentage of men find pictures with violent content a
turn-on as opposed to a turn-off?
Researchers developing drugs such as Viagra to improve sexual
performance also need a tool to measure the efficacy of the drugs
activity. The Rigiscan provides an objective measure of the level of
arousal in these types of behavioral and pharmacological studies.
Medical Diagnostics Many men, it turns out, are notoriously
unreliable at describing their own sexual performance. This may be
particularly true of men who have sought medical help for erectile
dysfunction or any other sort of sexual dysfunction. One the one
hand, some men are prone to overstate their prowess, thereby
under-reporting actual difficulties they may be experiencing. On the
other hand, some others may be very fearful of losing their ability to
perform, thereby over-exaggerating any perceived difficulties they may
be having. In these types of situations, an objective measure of
erections can be a useful tool for documenting actual erectile events.
Increasingly, the Rigiscan seems to be the tool of choice,
particularly for recording nocturnal erections.
Conventional wisdom has it that practically all men experience several
spontaneous erections each night while sleeping. For patients who are
experiencing erectile difficulties during their waking hours, it can
be medically useful, from a diagnostic point of view, to learn if they
have the same sort of difficulties at night, while they are sleeping.
And again, the Rigiscan is an important tool for recording nocturnal
The Rigiscan device consist of two rings that slip over the base and
tip of the penis. The rings are attached to a recording device that
monitors activity. A picture of the Rigiscan can be seen here:
The legend accompanying the picture notes that the Rigiscan measures
penile tumescence and rigidity. Tumescence refers to swelling,
and essentially measures the size (girth) of the penis. Rigidity
refers to stiffness, and is a measure of the ability of the penile
tissue to resist contracting (that is, the rings actually give the
penis a small squeeze, and record the degree to which the ring does or
A more detailed discussion of the operation of the Rigiscan can be
found in a newsletter article from the European Society for Sexual and
Impotence Research, here:
along with a graph of what they refer to as a normal nocturnal
pattern of activity, ranging from 4-6 erections per night, with good
quality erections. By this, they mean...well...exactly what most men
would mean by this phrase, I suspect....substantial rigidity (at least
70% by the Rigiscan measure), and erections that extend all the way
from the base to the tip.
On the graph, you can see that the Rigiscan produces four readouts
tumescence and rigidity at the tip, and ditto for the base. Reading
the graph is fairly straightforward, though there are a few
subtleties. During the night, this man experienced six substantial
erections, as evidenced by the six large peaks on all the graphs. The
fact that each graph pretty much mirrors the others is a sign of
normal erectile behavior swelling and rigidity acting in concert,
and the base and the tip both responding alike.
The first erection of the night is the longest, as evidenced by the
overall thickness of the peak. The others were considerably shorter
in duration, as shown by the much thinner peaks.
After the second erection, there is evidence of the beginnings of a
third one that didnt quite reach full status. You can see this about
a third of the way along the second graph (the rigidity graph for the
base) which shows a brief spurt (no pun intended) of rigidity at the
base, which is accompanied by only a small amount of activity at the
tip. There are a few other mini-events scattered throughout the
Another graph can be seen in the article here at the website,
Although the article itself discusses penile disease that can lead to
sexual dysfunction, the graph itself is described as a normal
Rigiscan graph, and shows one lengthy and two shorter full erections,
along with a few transient events.
As a final illustration, there is a graph in this presentation from
the Baylor College of Medicine on recovery from prostate surgery:
which uses Rigiscan results (see slide #27) to demonstrate the
effectiveness of nerve-graph function in restoring sexual function
I hope the information presented here fully answers your question.
However, if you find you would like additional information, just let
me know by posting a Request for Clarification, and I will be happy to
assist you further.
search strategy: search on Google and Google Images and
Altavista.com-Images for Rigiscan