One could argue that if a true zombie simulated empathy then whatever was required to allow it to simulate the empathy would have produced something nearly exactly like true empathy. You have to think about what would go into simulating empathy. The zombie would have to assess your internal state from external cues. It would have to understand that state in order to select the proper responses. Then it would have to react in such a way that you were convinced it understood what you felt. Once these three things have been achieved, you have empathy. It isn't simulated empathy anymore, it is true empathy.

I would say the same if two programs interacted the same way. If one had an internal state that the other correctly inferred from external cues and was able to communicate that back, I would see that as empathy. The inference can only be derived from knowledge of internal states that allows one to understand the other through minimal cues. It is possible to understand that internal state in another only through experience of the state. Even if the "experience" of the internal state has been programmed it can still be considered an experience. Using the knowledge of cause and effect one program can view the other and see its external state then recall its' own memory of an internal state that produced a similar external state. When it recalls the internal state it is experiencing empathy. The empathy becomes known to the other program when the empathic program communicates in a manner that convinces the other that it has accessed that internal state.

We don't peel open peoples brains to examine internal states. We perceive external cues that we use to do a look up in our own history of experience to find one that matches those external cues. We do not have to have the exact same experience as the person we empathize with in order to have an understanding of what they may be feeling. We can fake it, but unless we're pretty good actors or the encounter is short the deception will probably be known.

When we recall memories of events that produced similar external states we re-experience the emotions that are a part of the memory. When we do that, we then have tuned our own brains to a similar state as the person that caused us to search our memory. At that point both people in the encounter are experiencing similar feelings brought on by events that could be completely separate in time and space.

Empathy is one of the most important parts of social interaction. Someone alluded to its roots in a previous post. It might have been one of the first social behaviors that led to cooperation and communication.

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The only way of finding the limits of the possible is by going beyond them into the impossible.

Arthur C. Clarke

The Brain Science Podcast