So there is this 'new' book out (Seth Shulman, The Telephone Gambit: Chasing Alexander Graham Bell's Secret. New York : W.W. Norton & Co., 2008) on the race for the telephone patent between Alexander Graham Bell and Elisha Gray. According to an interview with the author, Seth Shulman, in the Sunday Herald (Glasgow, Scotland), the author discovered 'new' evidence that suggests that AGB received detailed information about EG's patent from a patent officer and subsequently, improved his patent application and hence, design:

I was able to find an affidavit by the telephone patent officer,
who was an alcoholic and indebted to Bell's law firm, who admitted he showed
Gray's notes to Bell. It was a pretty amazing thing to discover.

I hope (and I admit that I haven't been able to get a copy of the book yet) Mr. Shulman has more to offer than this 'new' evidence and argument because it has been published and argued many times before, e.g. in A. Edward Evenson's The Telephone Patent Conspiracy of 1876 (Jefferson N.C.: McFarland, 2000).
More interesting is Michael E. Gorman's approach. He analyzed Bell's and Gray's different mental models and their mechanical representations (experimental telephones) with the conclusion that AGB and EG pursued rather different problem solving processes and thus suggesting that their respective patent applications were the result of unique design strategies. (Michael E. Gorman, "Mind in the World: Cognition and Practice in the Invention of the Telephone." Social Studies of Science 27, no. 4 (1997): 583-624.)