http://www.lifehack.org/531982/science-says-guitar-players-brains-are-actually-different-from-everybody-elses?dgs=1
 

There are many things that influence bilateralism and bicameralism. (EDIT FOR MESH!)

EPH....WTH do you always have to go there?
 
Isn't it better to think with your upper faculties than you lower?

My wife has known this for as long as she has known me.

It's a fact Mesh...look it up!

No thanks....not interested in your scientology/cosmology.

From what I've seen some players are more abstract while others are more concrete in terms of how they approach music. If you had formal training or have taken guitar lessons for a long time you're probably applying the technical without thinking about it. Some have even deeper abilities.
 
It would make sense that we use whatever is at our disposal when playing with others. This probably includes reading people to a fine degree and picking up on what they're doing even on an emotional level. 
 
I just took one of those Myers Briggs tests. Very informative.
 
Some personality types have massive sensitivity to their surroundings, some of them know almost immediately what's coming off of a person and if they are telling the truth or not. Sometimes these things are described as feeling a certain "vibe". People routinely give off these vibes without realizing it. Some people are extraordinarily good at picking those up.
 
It would only stand to reason that if this kind of person is a musician, they can feel the vibe of the other players and follow it very well. I don't think this is only guitar players.

A few beers always helps me get into that 'vibe".

An article stating the very obvious about any competent musician capable of playing with others.

Equally applicable to any group activity relying on synchronising different people to do things together I would have thought. And switching off conscious thinking about the minutia of playing an instrument and going with muscle memory and rehearsed and ingrained habits applies to good instrumentalists, singers, typists, driving......

After all, all that practice is intended to get us to the point where we can play without thinking "press 1st finger left hand down behind third fret on 2nd string, pluck second string with plectrum, now press 3rd finger behind 4th fret on 3rd string, pluck 3rd string, bend string upwards a bit" all the time. And that applies to any instrument.

Nothing to do with whether someone learns material from sheet music or entirely by ear either, the mechanics are the same other than sheet music saves time working out what the notes are, though for many genres it doesn't convey style or 'feel' very well. And anyway, many musicians do both.

What I'd like to know is why I can co-ordinate my hands perfectly well enough to play guitar, bass, a few other stringed instruments and some of the accordion family but I'm hopeless at two-handed keyboard playing.

Starise
From what I've seen some players are more abstract while others are more concrete in terms of how they approach music. If you had formal training or have taken guitar lessons for a long time you're probably applying the technical without thinking about it. Some have even deeper abilities.
 

 
This is something that I have noticed to an even greater extreme in piano players.  There seems to be those who can improvise chords and notes on the piano; and those that have to have a piece of sheet music in order to play.  My daughter has taken piano lessons for years and I am guessing that she falls into the....has to have sheet music to play, category.