http://kajsotala.fi/2013/07/book-review-mindmelding-consciousness-neuroscience-and-the-minds-privacy/

I review William Hirstein's book Mindmelding: Consciousness, Neuroscience, and the Mind’s Privacy, which he proposes a way of connecting the brains of two different people together so that when person A has a conscious experience, person B may also have the same experience. In particular, I compare it to my and Harri Valpola's earlier paper Coalescing Minds, in which we argued that it would be possible to join the brains of two people together in such a way that they'd become a single mind.

Fortunately, it turns out that the book and the paper are actually rather nicely complementary. To briefly summarize the main differences, we intentionally skimmed over many neuroscientific details in order to establish mindmelding as a possible future trend, while Hirstein extensively covers the neuroscience but is mostly interested in mindmelding as a thought experiment. We seek to predict a possible future trend, while Hirstein seeks to argue a philosophical position: Hirstein focuses on philosophical implications while we focus on societal implications. Hirstein talks extensively about the possibility of one person perceiving another’s mental states while both remaining distinct individuals, while we mainly discuss the possibility of two distinct individuals coalescing together into one.

I expect that LW readers might be particularly interested in some of the possible implications of Hirstein's argument, which he himself didn't discuss in the book, but which I speculated on in the review:

Most obviously, if another person’s conscious states could be recorded and replayed, it would open the doors for using this as entertainment. Were it the case that you couldn’t just record and replay anyone’s conscious experience, but learning to correctly interpret the data from another brain would require time and practice, then individual method actors capable of immersing themselves in a wide variety of emotional states might become the new movie stars. Once your brain learned to interpret their conscious states, you could follow them in a wide variety of movie-equivalents, with new actors being hampered by the fact that learning to interpret the conscious states of someone who had only appeared in one or two productions wouldn’t be worth the effort. If mind uploading was available, this might give considerable power to a copy clan consisting of copies of the same actor, each participating in different productions but each having a similar enough brain that learning to interpret one’s conscious states would be enough to give access to the conscious states of all the others.

The ability to perceive various drug- or meditation-induced states of altered consciousness while still having one’s executive processes unhindered and functional would probably be fascinating for consciousness researchers and the general public alike. At the same time, the ability for anyone to experience happiness or pleasure by just replaying another person’s experience of it might finally bring wireheading within easy reach, with all the dangers associated with that.

A Hirstein-style mind meld might possibly also be used as an uploading technique. Some upload proposals suggest compiling a rich database of information about a specific person, and then later using that information to construct a virtual mind whose behavior would be consistent with the information about that person. While creating such a mind based on just behavioral data makes questionable the extent to which the new person would really be a copy of the original, the skeptical argument loses some of its force if we can also include in the data a recording of all the original’s conscious states during various points in their life. If we are able to use the data to construct a mind that would react to the same sensory inputs with the same conscious states as the original did, whose executive processes would manipulate those states in the same ways as the original, and who would take the same actions as the original did, would that mind then not essentially be the same mind as the original mind?

Hirstein’s argumentation is also relevant for our speculations concerning the evolution of mind coalescences. We spoke abstractly about the ”preferences” of a mind, suggesting that it might be possible for one mind to extract the knowledge from another mind without inherting its preferences, and noting that conflicting preferences would be one reason for two minds to avoid coalescing together. However, we did not say much about where in the brain preferences are produced, and what would be actually required for e.g. one mind to extract another’s knowledge without also acquiring its preferences. As the above discussion hopefully shows, some of our preferences are implicit in our automatic habits (the things that we show we value with our daily routines), some in the preprocessing of sensory data that our brains carry out (the things and ideas that are ”painted with” positive associations or feelings), and some in the configuration of our executive processes (the actions we actually end up doing in response to novel or conflicting situations). (See also.) This kind of a breakdown seems like very promising material for some neuroscience-aware philosopher to tackle in an attempt to figure out just what exactly preferences are; maybe someone has already done so.