Remote lie detection tests may soon be a reality
A new proof-of-concept may lay the foundation for lie detection tests wherein investigators will be able to remotely monitor blood pressure, pulse rate, and sweating among people without their knowledge or consent.
Experts at the Hebrew University of Jerusalem say that the shape of sweat ducts, the tiny tubes that connect sweat glands to the outside of the skin, is similar to that of some antennas.
According to them, the wavelength at which human sweat glands interact falls in the sub-terahertz (T-ray) range, which has recently been used in a variety of other applications, from uncovering hidden artwork to finding concealed weapons.
While sweating does not produce T-rays, sweat production changes the wavelength that is bounced back off the sweat duct antenna.
Designing a machine capable enough to measure these wavelengths, surmise the researchers, it may be calculated how much and where a person is sweating.
The researchers have also shown that monitoring the kinds of sweating based on where a person is sweating - such as on the forehead or on the chest and back - may make it possible to measure blood pressure and pulse rate remotely.
Currently, the only way to measure blood pressure is by using an inflatable pressure cuff or a surgically implanted monitor, and the only way to measure sweat is through a cumbersome process that uses electrodes on a small portion of skin.
The researchers say that the new method can do both remotely and constantly.
“This could open up a whole new area of research,” Discovery News quoted James Wolff, a doctor at Emerson Hospital in Concord, Massachusetts, who was not associated with the study.
As to how useful such a system can be for conducting lie detection tests, the researchers said that trained professionals could evade polygraphs made on the basis of their physiological responses like faster pulse, higher blood pressure, and increased sweating; however, if a person does not know they are being constantly tested, the new method could be more effective.
Jonathan Marks, a professor of bioethics at Pennsylvania State University, said that lie detection using this method would still have problems with accuracy, as a people anxious over something else at the time of tests could trigger a false positive.
“There are concerns about people’s privacy. Is there a justification for screening people en masse for physiological data? Where would you do this?” said Marks.
Source: NewKerala
Radio sweat gland — 90 GHz
The perils of perspiration
Sweat ducts in human skin act like an array of tiny antennas that pick up radiation at specific frequencies, according to researchers. The finding might one day be used in medical and security technologies to assess a person’s mental state from a distance.
A team of researchers in Israel has shown that sweat ducts pick up radiation at frequencies of about 100 gigahertz — the so-called extremely high frequency or EHF range, lying between microwaves and terahertz radiation. The antenna behaviour is all down to the ducts’ curious shape: they thread through the epidermis as regular helices. Filled with electrically conductive sweat, these channels act rather like coils of wire that absorb radiation across the millimetre and sub-millimetre wavelength band.
Yuri Feldman of the Hebrew University of Jerusalem and his colleagues directed a beam of EHF radiation onto the skin of the palms of subjects who had been jogging for 20 minutes, and measured the radiation that was reflected back. They found a strong band of absorption that was not seen before exercise. This absorption gradually disappeared as the subjects rested after jogging (Y. Feldman et al. Phys. Rev. Lett. 100, 128102; 2008). The researchers also found that the reflection signals were proportional to blood pressure and pulse rate — known indicators of physiological stress leading to sweating.
And when the researchers suppressed palm sweating with a synthetic compound that mimics the paralysis of snake venom, inactivating the sweat glands, they found that EHF absorption during exercise was markedly reduced.
The helical antenna array makes skin a kind of biological metamaterial, Feldman’s group says, in which the material’s response to electromagnetic radiation is determined by structure rather than composition. Metamaterials made from arrays of tiny electrical circuits are being explored for applications ranging from super-lenses to invisibility shields. “Nature has done what is being attempted extensively today in nanophotonics,” Feldman says. “This effect might be used for biomedical and homeland-security applications.”
Sweating hands have been used in lie detection, but using physiological parameters in ‘polygraph’ lie detectors is controversial and was strongly criticized in a 2002 report by the US National Academy of Sciences. “Perspiration is related to increases in emotional arousal,” says Paul Ekman, a psychologist in Oakland, California, and an author of the academy’s report. But he adds that “it can be the consequence of many different mental processes” — not only lying.
So far, Feldman and his colleagues are cautious about whether the idea will work at all, let alone how it might be applied. For example, they need to find the distance at which a meaningful signal can be detected and how long it takes for the signal to register changes in the biometric parameters. “We are just starting our journey in these uncharted waters,” says Feldman.
Source: Nature News