Nobody calls C3PO creepy eerie or spooky. But humanoid doppleganger social robots like Nadine are being found unsettling by many both because of their appearance and also due to ethical issues connected to the ways they may be used.

Nadine is a social robot made in the likeness of creator Professor Nadia Thalmann from Nanyang Technological University (NTU Singapore). Nadine is programmed with intelligent "assistant" software similar to Siri (the Apple computer program that works as an intelligent personal assistant) and Siri's Microsoft counterpart Cortana. Nadine however also expresses a version of moods and emotions with the ability to remember the people she has met before as well as conversations.

The problem for some experts is not the human-like appearance of such robots but rather moral and ethical questions about how they will be used. For instance would it be right to fool an elderly person into sharing his or her personal concerns with a robot with a human face? Or what about a child? Humanoid robots like Nadine can be programmed with child-rearing applications. But what are the ethics of using a robot like Nadine to fill in societal and personal needs? Can these actually be met by a machine that is not actually returning genuine responses and cannot provide an emotional connection?

"Looking at Nadine I'm worried that technology will make us forget what we knew about life" says Sherry Turkle professor of the social studies of science and technology at MIT author of "Reclaiming Conversation: The Power of Talk in a Digital Age."

So far Nadine has garnered much praise from robotics enthusiasts but she has also provoked a considerable amount of blowback on Twitter.

Turkle says in an interview that the psychological trigger that makes us shiver at the sight of something not quite human was termed "the uncanny" by Sigmund Freud. Roboticists call the gap between the point where a something goes from being comfortable to raising a red flag the Uncanny Valley.

"You start making a robot more and more like a person. It has two eyes it smiles better better better right" Turkle says. "And then you hit the point where 'Oh my Gosh!' it's starting to look like it could be a person and the fact that you're starting to respond to it like it's a person starts to creep you out."

So there's a sweet spot in robotics that roboticists have been pursuing for years she adds "where you can anthropomorphise but it will not creep you out".

"That sweet spot is what keeps roboticists honest because it keeps them from trying to pass them off as humans like 'Hello Barbie' which says 'I love you'" she says. "This is a representation no robot has the right to make. You can do an incredible amount of damage by marketing these to children and to old people as our new companions."

Turkle says: "I'm relieved that there is something in us that rejects that non-reality to protect ourselves."

Dr Arthur Bowman biologist at Norfolk State University says that protection is likely in part from the hippocampus a small curved formation in the brain that plays an important role in the limbic system.

"Humans look into eyes and into faces" Dr. Bowman says. "The hippocampus is reading what you are seeing and what you and maybe they too are feeling."

Therefore when the hippocampus and limbic system fail to detect any emotion in the eyes and faces of the robot the "uncanny valley" sends a warning shiver up the human spine.

Turkle asks: "Why would we be playing with fire on something so delicate as our children's feelings?

"Also when it comes to the elderly there you have roboticists happy that you can get the elderly to talk to robots but they're not thinking about who is listening."

"It breaks down the moral compact between generations that we're happy to get people talking to something pretending to understand" says Turkle.

Turkle recalls being called into observe an interaction between a humanoid robot and an older woman. "She was not a dementia patient just elderly and needing companionship and I saw her fooled into sharing her pain over the death of a child and it had a kind of obscenity that nobody was listening to her as she was trying to talk about her pain and the losses of her life."

She concludes: "It's important that not everyone stand around cheering that we have fooled an older person or a child but rather to have a conversation. I feel that absolutely just because we can do a thing doesn't mean we should."