

The Liar's Tell: Is Paul Ekman Stretching the Truth? - drjohnson
http://chronicle.com/article/The-Liars-Tell/149261/

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cowpig
"Ekman now admits it was a mistake to define micro-expressions by duration,
and describes them now as any facial expression that is very difficult to
detect in real time."

I can see why he regrets having made it--it's the only concrete, measurable
claim he made (that's mentioned in the article).

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nieve
I'ts been said before, but there's a major issue with any program that depends
on TSA officers' perception of people as liars or truthful: true positives are
going to be swamped by officer bias. In lower-stakes situations study after
study shows police officers presuming non-white people to be more likely to be
criminals without regard for local statistics. A terrorist group probably has
a higher chance of slipping a member by who is or can pass for non-Arab under
this setup. I doubt most domestic terrorists (almost universally white) are
going to get the same scrutiny no matter how nervous as a frustrated Arab-
American woman from Des Moines will. At best they might get checked in case
they were smuggling.

The model here relies on teaching officers to select people based on whether
they think they're lying, it's a perfect situation for prejudice to distract
from actual threats. Bruce Schneier and others have pointed how this wastes
resources and increases the attack surface for terrorists, but the TSA has
been highly resistant to feedback & criticism. It's the equivalent of having
the physical security guys for a building do sweeps at night to look for post-
its with passwords. That's not the computer security threat and it's not the
breaking & entering one, so why do you have them wandering around in the dark?

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lsiebert
Anxiety occurs for multiple reasons, so false positives would always be a
confounding factor, even if micro expressions occured 100% of the time.

There is quite a bit of evidence that even with physiological measures linked
to stress and lie detector machines, there is little reason to believe lie
detectors are especially effective. Given that non invasive means of detecting
anxiety are limited, and anxiety is itself limited, such screening is going to
not be helpful.

That said, there are some great studies on using recognition and EEGs or fmri
machines to detect lies. Your brain processes item's you recognize in
different ways, so if someone maintains they never were in an apartment where
a murder occured nor had seen it ever, you could display a series of
apartments, including the murder scene, and be able to tell when they
recognized the apartment. It's known in the field as the Guilty Knowledge
Test, or GKT. Check out the work by Farwell and others if you are interested.

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pjungwir
I don't know if Ekman is real or not (probably not), but any serious study of
predictions should report both precision (are your accused liars all guilty?)
and recall (did you catch all the liars?), not make statements like
"70-percent accuracy." Especially if we are using these techniques for
security screening, these numbers are essential. We'll also need to educate
security personnel about the unintuitive nature of false positives, where even
if a test achieves a low false positive rate, a given flagged person still has
a low chance of being a liar (see
[http://en.wikipedia.org/wiki/False_positive_paradox](http://en.wikipedia.org/wiki/False_positive_paradox)).

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Zigurd
Ekman is no less of of voodoo priest than polygraphers - an entire so-call
profession of witch doctors. He has cashed-in magnificently on a government
and population willing to buy empty high-tech looking boxes from a dowsing
practitioner to detect bombs.

~~~
socksy
If he's getting anything near what his skeptics are saying with somewhat
better than 50% accuracy after frame by frame processing and word analysis
(which would be the rather detrimental portrayal given in the article), then
he's doing a lot better than polygraphs. Polygraphs are a known pseudoscience.

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PhantomGremlin
It would be interesting to read an objective analysis of Israel's airport
security screening, to compare with what Ekman and the TSA have concocted.
There are plenty of glowing articles [1] about the Israeli "gold standard",
but I'm sure there are also plenty of glowing articles about Ekman.

It's certainly a field with many shades of gray. Not sure if most on HN can
relate to any of this, engineers are mostly about facts, about black and
white. Emotions don't have a lot to do with coding or debugging (except for
frustration, no shortage of that!).

[1] [http://www.huffingtonpost.com/daniel-wagner/what-israeli-
air...](http://www.huffingtonpost.com/daniel-wagner/what-israeli-airport-
secu_b_4978149.html)

