Steffi Paepcke, Lead User Experience (UX) Designer and co-founder at Open Source Robotics Foundation:

"We as humans can't help but project human-like qualities onto beings that are objectively not human. We relate to the world around us through a filter of our own experience, and often assume our own experiences or capabilities are generalizable. Think about that dog you see outfitted in a raincoat and adorable little boots. That dog's owner himself doesn't want to get wet, and extends that desire to his dog, who likely (but what do I know?) isn't perturbed by a bit of rain.

"My point is that we often can't help but assume that an entity is human-like in some capacity. This appears to be the case with robots as well. Robots such as the Paro and Pleo, seal and dinosaur simulacrums, respectively, elicit strong emotional reactions and care-giving tendencies despite our rational understanding that they are mere machines. If the goal is to evoke a more emotional response such as delight or affection, with few expectations of cognitive ability, a non-humanoid form is likely to be more successful than a humanoid. If your robot can carry out a small subset of tasks well (or poorly, for that matter), I think it best to steer clear of the human form factor, lest the real human in the interaction project more complex expectations onto the robot. Of course, if your robot is in fact more capable than its form lets on, you could be underselling your bot which will either pleasantly surprise your users, or deter them altogether.

"While an anthropomorphized miniature dinosaur and hopelessly defenseless seal may "require" our affection, they do not trigger within us the notion that they might equal us intellectually or physically, as a humanoid robot might. Once a robot takes on physically human traits, our expectations of its capabilities enter the realm of human as well. This can have powerful consequences.

"The most common consequence these days is disappointment. If we see a massive, bipedal machine attempting to open a door, we expect it to open the door. If instead it topples pathetically on its side, our expectations are not met and we may feel let down. We didn't expect sweet little Paro The Seal to open a door with its precious little fin, but this behemoth? It should have opened the damn door! When our eyes suggest that a robot might be human-like in its ability, our brain quickly follows suit. If the robot is indeed as capable as it appears, this is no problem. If, however, the robot topples at the door, our esteem for the robot dwindles, perhaps irrecoverably so."