duplicate photos on mac pro
I have a continuing problem. The photos on my Macbook Pro keep duplicating. I have 9.0.1 but the problem occurred with earlier versions. Why is this happening, how can I stop it happening again and again and thirdly, how can I delete the duplicates? I do not have my photos connected to iCloud and never have.
Many thanks indeed.
Mac Pro, Mac OS X (10.7.5)