Lol, I think we've all done this at one time in our lives. Basically, you know that saliva is meant to lubricate the mouth and protect bacteria from taking over. This is because our spat contains proteins, hormones and a myriad of other chemicals. Unfortunately, there is no direct link to why we may spit more when talking, but there are simple ways to control it. Firstly, since that saliva is there to stop infections and diseases in the mouth, brush your teeth more often, to avoid more production of the saliva. I carry around a toothbrush with me everywhere I go to control bad breath and dirty gums. Secondly, become more aware of your excessive saliva before speaking. Swallow it down, pause more often when talking and relax your body. When we are nervous or over excited, we produce more saliva than usual. So take a moment to rinse your mouth, suck in that extra saliva and pause more often when talking so that you don't create a build-up in your mouth. I hope this helped. :-D