Important!
So I need to clarify.
Contractors are not incapable of emotions, rather they just almost always reject them for their irrationality and because they can be a liability. The way they are able to do it, they do not feel nearly as vividly and it's usually to the point where they deny that they feel anything at all and believe it. However, sometimes emotions can pop up despite how much they may try to smother them. And should a Contractor finally accept having emotions, they will regain them in full, yet it will not much change their personality or tendency to be rational.
Dolls are simply incapable of expressing their emotions, and their emotions will usually start out quite dull but get more and more prominent with time and interaction so that eventually they may be able to express their feelings rather than remaining more blank than most Contractors. Though, they too, can develop personalities before emotions, it is just more rare for Dolls to do so.