TWO millivolts is not much. But it is enough to show that someone has seen something even before he knows he has seen it himself. The two millivolts in question are those associated with P300, a fleeting electrical signal produced by a human brain which has just recognised an object it has been seeking. Crucially, this signal is detectable by electrodes in contact with a person’s scalp before he is consciously aware of having recognised anything.

That observation is of great interest to DARPA, the Defence Advanced Research Projects Agency, one of America’s military-research establishments. DARPA’s Neurotechnology for Intelligence Analysts programme is dedicated to exploiting it in the search for things like rocket launchers and roadside bombs in drone and satellite imagery. To that end it has been paying groups of researchers to look into ways of using P300 to cut human consciousness out of the loop in such searches.

Among the beneficiaries are Robert Smith’s group at Honeywell Aerospace, in Phoenix, Arizona, and Paul Sajda’s at Neuromatters, in New York. Both of the “image triage systems” designed by these groups require the humans in them to wear special skull-enclosing caps (see picture). Each cap is fitted with 32 electrodes that record the brain’s electrical responses to whatever stimuli it is subjected to. Wearers have pictures flashed before their eyes at the rate of ten a second. That is too fast for conscious recognition, because the brain’s attention will have moved on to the next image before consciousness can come into play. It is not, though, too fast for the initial stages of recognition, marked by a P300 signal, to occur when suspicious items are present. Images that provoke such a signal are then tagged for review. According to Dr Sajda, this triples the speed with which objects of interest can be found.

Speed is important, of course. But in matters such as this, accuracy matters more. And some people think they can improve that, too—not by reading the brain, but by stimulating it. Many studies have shown that zapping the brain with a weak electric current, a procedure called transcranial neuronal stimulation, enhances what is known as “fluid intelligence”. This is the ability to reason, as opposed merely to recall facts. Another American military-research establishment, the Intelligence Advanced Research Projects Activity (IARPA), hopes to exploit this phenomenon for the purpose of target identification.

The notion of bathing brains in electricity spooks some. But with a current of just two milliamps, the stimulation is painless and safe, says Vincent Clark, a neuroscientist at the University of New Mexico. In a project paid for in part by IARPA, he and his team have stimulated the brains of more than 1,000 volunteers using a 9V battery connected to electrodes on the scalp. After half an hour of stimulation, volunteers spot in test photographs 13% more snipers, makeshift bombs and the like than do volunteers given a “sham” current of 100 microamps (5% of the experimental current) that mimics the skin-tingling induced by the experimental current.

Placing one of the electrodes on a volunteer’s arm boosts the phenomenon still further, according to Andy McKinley, head of brain stimulation at the American Air Force’s Human Effectiveness Directorate at Wright-Patterson, an air base in Ohio. This way, current travelling from one electrode to the other passes through more brain tissue than it otherwise would. Six hours after about 25 minutes of such stimulation, those so treated spot twice as many tanks, missile launchers and other targets in images as control groups manage to.

Nor do volunteers in these sorts of experiments seem to suffer ill effects. According to Dr Clark, the stimulation he uses makes a few feel drowsy, but most enjoy “a very deep mindful state”. Curiously, Dr McKinley reports almost the opposite. He says of his volunteers that when deprived of sleep they stay alert and cheerful longer. Some, he says, “feel like they’ve just had a bunch of caffeine”.

May the Force be with you

Sitting in a comfortable chair watching a computer screen, albeit while wearing a device that looks as if it was invented by a mad hairdresser, is one thing. Doing something similar while on patrol or dug into a foxhole is quite another. Yet this, too, is on DARPA’s metaphorical radar screen. The Cognitive Technology Threat Warning System, known to its friends as “Luke’s binoculars” (a reference to Luke Skywalker, a character in the “Star Wars” movies), is an attempt to take the idea of boosting target recognition into the field.

Luke’s binoculars, developed as part of a joint venture between Boeing and General Motors, combine image triage with 360° vision. Once again, participants must wear electrode skull caps. Actual binoculars are not involved, though. Instead, the cap-wearer looks at a screen which is being fed, in rotation and every tenth of a second, the images from six cameras, 60° apart, surrounding his position. If one of these images stimulates a P300 signal in his brain the system alerts him and lets him look properly at the image in question. In tests, people using Luke’s binoculars spot nearly twice as many threats as those scanning their surroundings with conventional field glasses.

Reading brain signals might also help prevent the misidentification as targets of troops that are on the same side as the cap wearer—and thus reduce incidents of death by “friendly fire”. In conjunction with the Australian and British defence ministries, America’s Army Research Laboratory, in Maryland, is analysing the brain’s alpha, beta, delta and gamma waves. These, unlike P300, are always running. But their strengths and frequencies vary according to what the brain is up to.

After deciding that he has seen an enemy, a soldier with his finger on the trigger takes between 400 and 450 milliseconds to pull it. But what if he changes his mind during that period? According to Jean Vettel, a neuroscientist who is working on the project, brainwave data can indicate that he has realised he has made a mistake in as little as 200 milliseconds. This should be enough time for a shot to be blocked by disabling the firing mechanism automatically, and for a comrade’s life thus to be saved. That idea really is a brainwave.