The cat we have has a somewhat unusual history.   I repeat it here because it
would seem to me to have some bearing on it's behaviour - I just don't know what
bearing...

It's two years old, having spent the last 3 months in our house.

Before that, my daughter had it (along with a half-dozen horses, four dogs, an
unknown number of chickens, four house cats, and an unknown number of barn cats.

She had it for about nine months, having gotten it from a girl who picked it up
off of a Philadelphia back alley as a kitten - preseumably part of a feral cat's
litter.

The girl had a boyfriend.... the boyfriend didn't like the cat and is presumed
to have abused it when she wasn't around - certainly the cat reacts strongly to
a raised hand.    Hence the transfer to my daughter's.

At my daughter's, the cat got along with all the animals except the other cats.
Every time a cat would approach, this cat would hiss and, if the other got too
close, attack.   One of the other cats - after trying to make friends with this
thing for some time - seemed to turn on it and apparently took it as it's
mission in life to kill it.    Beeeeeg time cat fights in the house, chasing it,
stalking it for day after day....  

At first, this cat didn't allow people to even approach it, much less touch it.
My daughter's husband domesticated it somewhat by putting on welding gloves and
just being persistant - letting it bite and claw the leather gloves instead of
him.  After awhile, no gloves needed and it seemed tb comfortable around him.

The precipating factor for moving it to our place was onset of winter and the
anticipated cat fights in the house.

It's actually come around quite a bit in the three months with us.   It even
gets along with one of the neighbor's cats to the point of following it around
and playing with it.

It doesn't hiss or claw at us anymore and sometimes actually comes up to us to
be petted and/or sits in our laps.   It even understands "no".

I figure this thing will continue to become more domesticated/trusting over
time, but don't expect it to ever be normal - but that's ok because as-is it's
kind of attractive... a cat with attitude, so-to-speak.

But, to cut to the chase:  it still bites.  It doesn't bite hard any
more...broke the skin on my wife's wrist once, but that was over a month ago and
now it's just more of a gesture/communication device than an attack.

I can see it biting when somebody pets it and it doesn't want to be petted...
and we've had some success with just withdrawing attention from it for awhile
when it does that - and we'll try the suggesion to make a high-pitched sound to
help it realize that it hurt somebody.

But the biting that puzzles me occurs under different circumstance.

For instance yesterday I was laying on the couch reading the paper.   This thing
comes up, jumps up on my chest, sticks it's nose in my face - all very friendly.

It purred and kneeded me for a few minutes, I stroked it a little and then it
laid down on my legs - facing towards my feet.   I'm laying there, holding the
paper with one hand.   The other hand is laying on my left leg - not moving at
all.   Suddenly the cat twists around, lunges at my hand, bites it, and then
starts licking it.   Then it starts grooming itself in a manner that seems to me
to be excessive.  

This seems to be a pattern.   Unprovoked bite, lick the area, then groom
intensively.

Could this be some sort of anxiety reaction to the bite?  

I don't have a problem with the biting any more - it's gentle enough that I just
take it as communication... but the pattern puzzles me.... Is this thing trying
to tell me something or is it just a little psycho?