(Inside Science) -- Now, I don’t want to alarm anyone, but telepathy, the act of transferring thoughts into someone else’s head is now real. As in, published-in-academic-papers real. People have now telepathically communicated with each other, monkeys have solved problems as a connected hive mind, and humans have even been given telepathic control of a rat. So, how exactly did we do it?

The brain transmits messages as electrical signals through nerves. But we can’t just connect everyone’s heads through a giant web of nerves -- even if we could, it would be impractical.

But we can read the electrical activity from brain cells with electronic devices. Then transmit the signal, like we do the internet, and turn it back into brain cell activity at the other end.

Unfortunately, this is where it gets tricky. First, how exactly do you read brain activity? Implanted electrodes can do it -- they sense the change in electrical currents as brain cells activate. But unless you fancy having complicated surgery to cover the entire surface of your brain in a fine array of electrode needles, you’ll have to choose option two -- electro encephalography, or EEG.

EEG rests a collection of larger electrodes on top of your head, where it records the electrical activity of larger groups of cells. But that is only after the signal has passed through the meninges, skull and the skin. So, it is not so accurate. But it’s the only one that human telepathy studies have actually used.

And now, an unexpected problem: How do we decode the signals we’ve got? We actually still don’t understand how the brain codes electrical information. It would be like we can hear the brain thinking, but we have no clue about the language that it’s speaking. Except that it’s going to be really complicated.

To work around this, telepathy studies have got people to produce simple, stereotypical EEG activity. You can do this right now: Just imagine moving your hands and feet. (Don’t actually do it, just imagine it.) Your brain is now making that same stereotypical electrical activity. There are only a few of these simple EEG patterns we can make -- so it’s like the people in the study could only beam out a few different words.

Now for the hard part: How do we beam a thought back into someone else’s head?

If you went for the electrodes option back in part A, then we could do it just by passing some current back into the electrodes, although we’d have very little control over what kind of thoughts we stimulated.

If you’re not wired up for that, then you could do it magnetically. And to do that, you’ll need a Transcranial Magnetic Stimulation wand, which creates a strong magnetic field at its tip. Rest it on your head and turn it on, and a magnetic field momentarily passes across the brain tissue directly beneath it, inducing a current that activates that brain tissue. Unfortunately, this has even less control than the electrodes -- but if you place it over the visual cortex, it can be reliably used to trigger little flashes of light called phosphenes.

Put all of this together and you have the first demonstration of telepathy: One person concentrates on something in particular, this is read as specific EEG brain activity, that is sent by wire to a TMS wand, and that stimulates another person’s brain and they see a flash of light. That was done back in 2014.

But in a way, I think we’ve been doing telepathy for a lot longer than that. In fact, if the definition of telepathy is sending messages from brain to brain, we’ve been sending messages to each other since we squelched out of the primordial ooze. Culminating in the most sophisticated communication system we know: language and gesture. And then mobile phones.

But maybe that doesn’t really count. That’s not “real” telepathy -- not sent directly brain-to-brain: It has been filtered through our senses.

But then maybe this new telepathy doesn’t count either -- because the only way we can beam “thoughts” into people’s heads is by activating their sensory brain regions, triggering sensations, in this case to trigger phosphenes.

Maybe it’s best described as a “prelude” to telepathy. A proof of concept rather than a functioning system. The technology to bring all those steps up to scratch for proper thought transmission still doesn’t exist. And even if it did exist, we still need to work out how to understand the brain’s language first.

But with projects like Elon Musk’s “Neuralink” on the horizon, that day may come sooner than we think. So, I’ll leave you with a question: Language -- our telepathy 1.0 -- has so far always been the filter for our thought transmission. What does a thought without language sound like?