Researchers at Stanford University studying the physiological impact of human-on-bot contact found that "touching areas perceived as private made the skin more moist," NBC News reported.
The team of scientists programmed a two-foot-tall robot — part Michelin Man, part Wall-E — to command four female and six male subjects to touch various parts of its body. Study participants wore finger sensors to measure arousal and reaction time.
When asked to touch a neutral, easily accessible part of the body such as the hand, there was no marked response.
However, when instructed to touch the robot's buttocks, participants not only took longer to respond but showed a "measurable increase" in skin conductance, or high emotional arousal. The researchers found that "physiological arousal was inversely related to accessibility" — meaning that touching bottoms came up tops.