It was/is widely thought that dogs bark for a number of reasons, such
as defending the home front against intruders, or to say "come play
with me", just to name two examples. This new study sheds light on an
old age question "why do dogs bark?" Conflict at the core of it all.
"Dogs bark more because they are put into conflicting situations.", Kathryn Lord.
Study by Kathryn Lord and colleagues at UMass Amherst http://www.sciencedaily.com/releases/2009/07/090714210137.htm
This was posted previously - lost