"Pets that are out of their comfort zones can have behavior problems in the car, which can be dangerous while driving, " says Hammer.

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But that's little comfort to a parent whose child's behavior can range from quirky to violent.

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They carefully define trust and craft guidelines for acceptable behavior based on their level of comfort with risk and fluidity.

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In their study, just published in Computers in Human Behavior, they say that Dr Mori's ideas of familiarity and comfort level do not properly get at the quality of uncanniness.

ECONOMIST: Animation and robotics