[IP] more on Which Travelers Have 'Hostile Intent'?
Begin forwarded message:
From: Gene Spafford <spaf@xxxxxxxxxxxxxxxxx>
Date: August 21, 2006 9:44:20 PM EDT
To: dave@xxxxxxxxxx
Cc: ip@xxxxxxxxxxxxxx
Subject: Re: [IP] more on Which Travelers Have 'Hostile Intent'?
Begin forwarded message:
From: "David P. Reed" <dpreed@xxxxxxxx>
Date: August 21, 2006 4:08:42 PM EDT
To: dave@xxxxxxxxxx
Subject: Re: [IP] more on Which Travelers Have 'Hostile Intent'?
David Farber wrote:
This sounds like alie detector and they have been proven not to
work djf
While I completely agree with that statement, nonetheless the USG
continues to use them, and its security services continue to claim
they are reliable.
I don't think there's a hope in hell of getting them to listen to
reason. Just as a substantial percentage of the American public
believes that psychics have helped police solve many, many cases.
The following is a general discussion. I am in no sense an expert on
lie detectors, but this is how it was explained to me by some who are
very familiar with the issue.
Lie detectors have a non-zero rate of error. As with many real-world
systems, these errors manifest as Type I errors (alpha error, false
positive) and Type II errors (beta error, false negative), and
instances of "can't tell." It's important to understand the
distinction because the errors in any system may not be equally
likely, and the consequences may be very different. An example I
give to my students is after going over a proof that writing a
computer virus checker that accurately detects all computer viruses
is equivalent to solving the halting problem. I then tell them that
I can provide them with code that identifies every program infected
with a computer virus in constant running time. They think this is
a contradiction. I then write on the board the equivalent of
"Begin; print "Infected!"; End." -- identify every program as
infected. There are no Type II errors. However, there are many
Type I errors, and thus this is not a useful program. But I digress....
I have been told that lie detectors more frequently exhibit Type I
errors because subjects may be nervous or have a medical condition,
and that Type II errors generally result from training or drugs (or
both) by the subject, although some psychological disorders allow
psychopaths to lie undetectably. Asking foil questions (asking the
subject to lie, and asking a surprise question to get a reaction)
helps to identify individuals with potential for Type II errors.
Proper administration (e.g., reviewing the questions with the subject
prior to the exam, and revising them as necessary to prevent
ambiguity), helps to minimize Type I errors. [Example. When
granting a security clearance, you want to weed out people who might
be more likely to commit major crimes, or who have committed them
already and not yet been discovered (they may be more prone to
blackmail). Thus, you might ask "Have you committed any crimes you
haven't disclosed on your application?" Someone very literal-minded
might think back to speeding down the Interstate this morning, lying
to buy beers at age 20, and so on, and thus trigger a reaction.
Instead, the examiner should explain before the exam that the
question is meant to expose felonies, and not traffic violations and
misdemeanors.] "Can't tell" situations are resolved by giving the
exam again at a later time, or by reporting the results as ambiguous.
In a criminal investigation, any error can be a problem if the
results are used as evidence.*** For instance, if I ask "Did you
commit the robbery?" and there is a Type I error, I would erroneously
conclude you were guilty. Our legal system does not allow this kind
of measurement as evidence, although the police may use a negative
result to clear you of suspicion. (This is not generally a good step
to take in some crimes, because some psychopaths are able to lie so
as to generate Type II errors.) If I asked "Are you going to hijack
this plane?" then you might be afraid of the consequences of a false
reading, or have a fear of flying, and there would be a high Type I
error rate. Thus, this probably won't be a good mechanisms to screen
passengers, either.
When the US government uses lie detectors in security clearances,
they aren't seeking to identify EXACTLY which individuals are likely
to be a problem. Instead, they are trying to reduce the likelihood
that people with clearances will pose a risk and it is judged as
acceptable to have some Type I errors in the process of minimizing
Type II errors. So, as with many aspects of the adjudication
process, they simply fail to grant a clearance to people who score
too highly in some aspect of the test -- include a lie detector
test. They may also deny clearances to people who have had too many
close contacts with foreign nationals, or who have a bad history of
going into debt, or any of several other factors based on prior
experience and analysis. Does that mean that those people are
traitors? No, and the system is set to not draw that specific
conclusion. If you fail a lie detector test for a clearance, you
aren't arrested for treason! * The same if your evaluation score on
the background investigation rates too high for lifestyle issues.
What it DOES mean is that there are heightened indications of risk,
and unless you are "special" for a particular reason,** the
government chooses to not issue a clearance so as to reduce the
risk. Undoubtedly, there are some highly qualified, talented
individuals who are therefore not given clearances. However, they
aren't charged with anything or deprived of fundamental rights or
liberties. Instead, they are simply not extended a special
classification. The end result is that people who pass through the
process to the end are less likely to be security risks than an equal
sample drawn from the regular population.
The same screening logic is used in other places. For instance,
consider blood donation. One of the questions that will keep a
donation from being used in transfusions is if the donor is a male
and indicates that he has had sex with another male since (I think)
1980. Does that mean that everyone in that category has hepatitis
or HIV? No! It only means that those individuals, as a class, are
at higher risk, and they are a small enough subset that it is worth
excluding them from the donor pool to make the donations safer in
aggregate. Other examples include insurance premiums (whether to
grant insurance to high risk individuals), and even personal
decisions ("I won't date women with multiple facial piercings and
more than 2 cats -- too crazy.") These are general exclusions that
almost certainly include some Type I errors, but the end result is
(in aggregate) less risk.
Back to lie detectors. There are two cases other than initial
screening that are of some concern. The first is on periodic
rechecks (standard procedure), and when instituting new screening on
existing employees, as was done at some of the national labs a few
years ago. In the case of periodic rechecks, the assumption is that
the subject passed the exam before, and a positive reading now is
either an indication that something has happened, or is a false
positive. Examiners often err on the side of the false positive in
this case rather than triggering a more in-depth exam; Aldrich Ames
was one such case (unfortunately), and he wasn't identified until
more damage was done. If one has a clearance and goes back for a re-
exam and "flunks" it, that person is often given multiple
opportunities to retake it. A continued inability to pass the exam
should trigger a more in-depth investigation, and may result in a
reassignment or a reduction in access until a further determination
is made. In some cases (which I have been told are rare) someone's
clearance may be downgraded or revoked. However, even in those
cases, no statement of guilt is made -- it is simply the case that a
privilege is revoked. That may be traumatic to the individual
subject, certainly, but so long as it is rare it is sound risk
management in aggregate for the government.
The second case, that of screening people for the first time after
they have had access already and are "trusted" in place, is similar
in nature except it may be viewed as unduly stressful or insulting by
the subjects -- as was the case when national lab employees were
required to pass a polygraph for the first time, even though some had
had DoE clearances for decades. I have no idea how this set of exams
went.
Notes to the above
* -- Although people flunking the test may not be charged with
treason, they may be charged with falsifying data on the security
questionnaire! I was told of one case where someone applying for a
cleared position had a history of drug use that he thought would
disqualify him, so he entered false information on his clearance
application. When he learned of the lie detector test, he panicked
and convinced his brother to go take the test for him. The first
question was "Are you Mr. X?" and the stand-in blew the pens off the
charts. Both individuals were charged and pled guilty to some kind
of charges; neither will ever get a security clearance! :-)
** -- Difficult and special cases are when someone, by reason of
office or designation, is required to be cleared. So, for instance,
you are nominated to be the next Secretary of Defense, but you can't
pass the polygraph as part of the standard clearance process. This
goes through a special investigation and adjudication process that
was not explained to me, and I don't know how this is handled.
*** -- In most Western world legal systems. In some countries, fail
the polygraph and get a bullet to the head. The population is
interchangeable, so no need to get hung up on quibbles over
individual rights and error rates. Sociopaths who can lie and get
away with it (Type II errors) tend to rise to the top of the
political structures in these countries, so think of it as evolution
in action....
So, bottom line: yes, lie detector tests generate errors, but the
process can be managed to reduce the errors and serve as a risk
reduction tool when used in concert with other processes. That's
how it is used by the government.
--spaf
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