When do suggestions become collaboration?

Over the years I've collaborated on a handful of articles and short stories--the most recent being "Snowbird," written with Tom Sweeney and published in Ellery Queen Mystery Magazine back in December 2007. In each case my co-author and I entered into the collaboration knowingly and with clear intent.

Joe, my best friend in high school, and I alternated time at the keyboard. I would write a sentence or two and then he would write a sentence or two. We wrote faan fiction (fiction about science fiction fans) and some of what we wrote was published in science fiction fanzines. These were usually published under a pseudonym because Joe and I were characters in the stories.

In college, Walter and I collaborated on articles for the college paper. We played to our strengths. He did most of the research and I did most of the writing. We shared the bylines and split the money.

My second wife, Pamela, made a game of it. She would write an opening scene and then challenge me to write the rest of the story. A few of these stories were published under my name, but most appeared under pseudonyms. (And a few unfinished stories linger in files many years after her death.)

Tom and I collaborated in a more "intimate" fashion. We discussed everything and we revised each other mercilessly. When I look at the final, published draft of "Snowbird," I can identify only half a sentence as "mine," and the finished story represents the first sale either of us made to Ellery Queen.

Rebecca--whom I have referred to as "Plot Monkey" or as "my plot monkey" in previous posts--seem to be stumbling toward collaboration. A few years ago I referred to the old adage that if you put enough monkeys with enough typewriters into a room together, sooner or later they'll write the complete works of Shakespeare. At the time I said I didn't need all of the monkeys, just the plot monkey. I thought if I had someone to help plot I could increase my productivity.

Enter Rebecca, a voracious reader but non-writer. Over dinner one evening I mentioned two stories that I had half written and hadn't finished because I couldn't figure out the rest of the plots. By the time we left the restaurant, we had roughed out the plots for the last half of each story.

I finished writing and sold those stories.

We've had dicussions about other stalled stories since then, and one day earlier this year I saw a note from an editor looking for stories to fit a particular holiday theme. I had nothing finished, nothing in progress, and no ideas for a story that fit the theme. I mentioned this to Rebecca. The next day she emailed me a rough plot and the backstory that propelled the plot.

I wrote and sold that story.

The story I wrote Sunday came from a plot Rebecca and I devised after riding the Texas State Railroad on Saturday. This time she did more than just help plot. She also helped with characterization and suggested ways to revise parts of what I'd written. I even included a sentence she wrote in the final draft.

I submitted the story under my byline, but I'm left wondering: When do suggestions become collaboration? At what point does the help someone gives you justify sharing the byline, the income, and whatever fame and glory might follow?

I don't have an answer. Do you?