What is a scientifically plausible method by which people might in the future be able to read minds? I am writing a book. It will be post-apocalyptic, and the apocalypse I'm thinking of will involve people being able to read each other's mind. Can any of you give me a slightly plausible reason that this would happen / be possible?
If you don't need the mind readers to actually know the exact "words" of the person's thoughts, you could have people who are extremely well versed in "reading" another person's facial expressions, body posture, tone of voice etc. It is a fact that those outward behaviors reflect your internal state, and in fact we all read these signs with more or less accuracy, but there are a few people (and maybe you can train that) who are better than others to deduce how you feel and what you might be thinking from these. (see "cold reading")

If you need actual mind readers, we are currently arriving at a point where we begin to be able to interpret fMRI images. There are some experiments where researchers were able to tell which images a test subject was looking at or which body parts they were moving from looking at their brain activity alone. I'm sure that our understanding of what goes on in the brain will progress and the technology to measure brain activity will get smaller and more exact, so you could have people use a device that reads minds. It is quite likely that such a device will exist in the not too far future.

If, finally, you want real telepathy (which, just to cause no misunderstanding, cognitive scientists believe does not exist) you might base it on:


an organ in human beings sensitive to magnetic or electric fields, sensing (like EEG) the brain states of another human being; there are animals who can sense electricity or magnetism, but the problem with this is that magnetism surrounding us is stronger than that coming out of the brain and will make it impossible to "feel" a brain from farther than a few centimetres away
this organ might be in the skin (actually not one organ but many receptors) so the reader could cover the head of the person to be read with his hands, much like an EEG cap
the reader would need to be trained with people telling them what they think while he "feels" their brain, so that he can learn which "sensations" in his hands correspond to which thoughts and cognitions
maybe its possible to clone human beings with specific animal genes so that humans grow electrically or magnetically sensitive receptors, e.g. in their hands (research animals with electric and magnetic senses and how their receptors work)


I'm just trying to extrapolate (my understanding of) current research, here. I cannot foresee future discoveries either technological or psychological, so I'm keeping this within the realm of the possible as much as seems plausible to me. Again: We don't think telepathy in the traditional sense (concentrating your mental powers and knowing what someone thinks) exists. If you want that, I don't see how it could be possible.



There seems to be some evidence of magnetoperception in humans:


http://en.wikipedia.org/wiki/Magnetoception#In_humans
http://www2.pe.tu-clausthal.de/agbalck/biosensor/magnetsinn.htm


It is easy to imagine that this sensitivity to the earth's magnetic field might develop to discern even the much weaker magnetic fields of the brain. After all, the other senses show a huge variety between species, too. For example, the silk moth can detect single molecules of a female's pheromones. The current sensory ability of humans is not a fixed limit for how sensitive a sense can be. If the magnetism of the brain can be measured by an artificial detector, then it can potentially be measured by a biological detector.