The military has a genuine interest in brain stimulation research.

Photograph: Alamy

About five years ago, not long after I started up my research group at Cardiff University, something rather strange happened. One morning I came down to my lab to find the door wide open and a suited man standing in the middle of the room, peering around and scribbling on a clipboard. He told me he worked for a private defence firm who were interested in applications of my research on human brain stimulation. He also said there was funding available for joint research projects. We spoke for a couple of minutes before I made it clear I wasn’t interested in that sort of collaboration.Thinking about it afterward, something about the encounter chilled me. It wasn’t the fact that this person had gained access to the lab seemingly unannounced, and it wasn’t even the sense of entitlement that seemed to exude from the guy, as though he was standing in his lab not mine. What bothered me was the realisation that the work I do operates anywhere near the line where a military firm might find it useful. My opinion at the time – still unchanged – was that I would sooner quit science than get into bed with the profiteering wing of those whose raison d’être is foreign intervention and invasion.

Five years later, brain stimulation research has moved far and fast. A fascinating new issue of Frontiers in Human Neuroscience includes a timely review on the various ways brain stimulation can enhance thought and behaviour – with special consideration of applications in the security services and military.

Different forms of neurostimulation in humans have now been shown to boost our ability to learn and perform motor actions, to pay attention to events in the environment, to recall information in memory, and to exercise self-control. At the same time, evidence is mounting for more complex effects on cognition. For instance, stimulation of the human prefrontal cortex can enhance or inhibit our tendency to lie, improve our ability to lie successfully, and can encourage us to comply with social norms that carry a punishment for disobedience.

Most of these findings stem from two basic forms of brain stimulation. The first, called transcranial magnetic stimulation (or TMS), uses the physics of electromagnetism to activate brain cells. How this activity influences behaviour depends on what the brain cells are important for in the first place. So, were I to apply TMS to a particular part of your motor cortex then it would make your finger twitch, but if I instead stimulated Broca’s area then it would disrupt your ability to speak.

The second major approach, called transcranial direct current stimulation (or TDCS), works quite differently. TDCS is generally too weak to make brain cells fire – instead it alters the sensitivity of the cells, making them more or less active in response to something that stimulates them later. Both TMS and TDCS can have aftereffects lasting from minutes to hours, sometimes even days, causing changes in neurophysiology and neurochemistry.

As the scientific questions being asked by brain stimulation expand, so too are the methods becoming more sophisticated. One exciting new technique, called transcranial pulsed ultrasound, theoretically allows precise stimulation of any neural region. So far it hasn’t been tested in the human brain but such studies seem only a matter of time. Together, these techniques and their applications hold great promise for understanding the machinery of human mental processes, with hope for treating patients suffering from brain injury and disease.

Well, at least that’s the line that we use in our grant applications and press releases. And it’s true, except that it doesn’t tell the whole story because anything that can boost or rehabilitate human abilities could also be exploited for military or security purposes, as well as by questionable private enterprises. Predictably, some of the major innovations in brain stimulation research are being funded by the US military.

So far the applications of brain stimulation proposed by the military are far-fetched, but what happens when the science catches up with their ambitions? What army wouldn’t take advantage of a method that could make soldiers more alert, faster to react, faster to learn, less likely to binge-drink off duty, and more compliant with authority? What intelligence agency wouldn’t embrace a technology that could help their operatives become better liars, or which limits the ability of prisoners to lie under interrogation?

Applications like these, in turn, raise ethical questions. Would a soldier be able to refuse brain stimulation, and if not, wouldn’t that violate the principle of consent underlying ‘medical’ interventions? Would soldiers under the influence of brain stimulation still be accountable for their actions in conflict? Would a prisoner subjected to brain stimulation lose their right to silence?

Going deeper we might ask whether it is ethical for neuroscientists and psychologists to collaborate with organisations whose ultimate research objective is to develop more efficient ways of killing people. How, we might wonder, do such activities fit with the benign aims of the Society for Neuroscience or the British Psychological Society?

Fortunately we’re still some distance from a future of routine neuro-enhancement and, as always, we should be wary of hype that suggests otherwise. Among the cognitive neuroscience community there is much valid scepticism about the potential of brain stimulation to genuinely improve neural function. It could be that, like a zero-sum game, improving any one function necessarily impairs another.

Even so, the dazzling pace of brain stimulation research warns us not to downplay the interests of the military and private industry. Whether such concerns should hinder the progress of basic science is a vexed issue. Few of my colleagues would accept that advances in neuroscience should be limited beyond consideration of whether the research itself is ethical. After all, they would say, who can possibly foresee all the unethical applications of basic science? I agree, but the argument has one problem: when it comes to brain stimulation, there is a foreseeable future in which the neuroscience becomes enmeshed with the politics of security and war.

As Western governments cut basic science funding and push academics toward working with industry, it is easy to see why those in my position may be tempted to align with wealthy defence contractors. Yet in the race to achieve REF impact, society may well ask who is assessing the risk of that impact being harmful