There seems to be a lot of confusion concerning this question.
The following text (provided by Netrunner) should provide a better understanding of the situation.
Firstly we have to make a distinction:
a. Reps have programmed emotional responses that are built in to make them seem like Humans. These are not real emotions and the Reps don’t *feel* them – they are simulations of the responses that Humans give. These are what allow Reps to interact with Humans and help them to appear Human.
b. Some Nexus 6 Reps have started developing their *own* emotional responses. And these *are* real emotions. It is the first stage to the eventual possibility of them developing empathy (as we see in Roy at the end).
The V-K test measures a number of physical responses to the questions. These add up to a measurement of empathic response. The Reps respond with answers and programmed physical responses. Humans respond naturally. I am sure there are aspects of the test that I “don’t know” but certainly one aspect is, for example, not just measuring things like how much of a blush response there is, but the speed at which it happens. Reps and Humans have the same basic responses, but at different levels and speeds. (Note that the V-K machine predates Nexus 6 Reps and was designed to identify Reps that had no true emotional responses of their own, hence the question of whether it will still work in identifying Nexus 6 Reps.)
There may also be some questions that allow Reps to make mistakes. For example (from DADoES), “Your husband hangs a picture on the wall of a naked girl lying on a bearskin rug – how do you respond?” Well, if you’re a human in this post-apocalyptic world, you respond to the fact the rug is bearskin and ignore the naked girl part. If you’re a Replicant, you might miss that point.
Posted in: 4.3. Replicants