It all depends on the school and the professor. Some schools will give you a year or two worth of credit for your master's, while others will make you start from scratch. Same goes for the faculty members you want to work with, some faculty members will not take students with a masters. The best thing to do is research Ph.D. programs that you want to attend and determine their policy for admitting students with a master's. The best option is to go straight into a Ph.D. program, if at all possible. If getting a master's is your only route into a Ph.D. program, you may want to go with an experimental master's unless you're 100% sure developmental is the route you want to take. Otherwise, even if the Ph.D. program will take transfer credits, you will still spend a couple of years making up classes because you changed directions. I should know, I am getting my master's in general/experimental psychology and the education was fairly broad. I self-specialized in neuropsychology and quantitative, only to end up getting accepted to a cognitive science program. So, essentially...I'll probably only get a year or so taken off the standard 5-year program. Talk about a waste of time and money. If I knew I would be in this boat earlier, I would have taken different coursework.