Humans can’t fly. They aren’t among the fastest animals on land or in the water. They don’t have claws or horns or other natural defenses.
Yet the human anatomy serves as the model for many robots both real and fictional, most recently in the movie “Pacific Rim.”
Roboticists have an almost unlimited supply of references and structural models from the world of animals and even plants.
Yet human-shaped robots abound. The idea of the “mecha,” a human-shaped giant fighting robot, has become an entire subgenre all its own.
There’s certainly some kind of “poetic” appeal to a human-shaped robot. But are there any structural advantages? Why would anyone make a human-shaped robot?
Mecha my day
“There are good reasons to build robots in the shape of humans,” said Jekanthan Thangavelautham, a robotics postdoctoral associate at the Massachusetts Institute of Technology. “Bipedal or legged robots are ideal for traveling in rugged terrain, uneven and soft environments.
“It makes better sense if [the bipedal robots] are within a few times the size of humans, i.e 1.5 to 2 times,” Thangavelautham added, explaining the benefits start to decrease at larger sizes because the robot’s weight and size will start to present unique design challenges.
Humanoid robots would also be very capable of handling human-built terrain such as sidewalks, stairs and elevators.
Climbing up stairs is one thing— which, by the way, roboticists still struggle to recreate. But what if you want robots to cross rougher terrain?
Andy Ruina, a professor of robotics at Cornell University who specializes in “legged locomotion,” is more skeptical of a humanoid robot’s advantages. “You’d have trouble naming a problem where…a human shape is the best solution,” he said. “Unless [the problem] was ‘look like a human’ or ‘interact with a human’ or something like that.”
For other tasks, Ruina suggests that roboticists should look elsewhere in the animal kingdom for inspiration.
“All kinds of animals and machines are good at crossing rough terrain. People are a teeny fraction of the animals that get around on this planet,” Ruina said. “[The human form] is certainly good enough, right; we’ve been around a few million years. But there are designs that have been around longer. Cockroaches have been around a lot longer than humans have and probably will be around [after we’re gone] too.
It looks like people
The human form might not be the most efficient when it comes to swimming, running or fighting giant monsters, but there’s another advantage to humanoid robots: the idea appeals to humans on a psychological level.
“It’s widely understood that we as humans prefer interacting with robots that somewhat look like us,” Thangavelautham said. “We like to interact with robots that look like us but not too much, otherwise we find it creepy.
This concept, Thangavelautham explained, is called the “uncanny valley.”
The idea is that the more humanlike a character or artificial intelligence’s appearance is, the more easily humans will relate to it. However, at a certain point the humanlike character or artificial intelligence starts to look “too human.” At that point, imperfections such as jerky movements, blank eyes or strange behavior become impossible to overlook or dismiss; instead of an endearingly humanlike character people see a freakish parody.
That drop is called the “uncanny valley.” It’s why digital animation companies like Pixar often choose to make movies about anthropomorphic animals or objects instead of attempting realistic humans.
The term “uncanny valley” is most often used today to describe the challenge of creating photorealistic digital graphics, but it was originally coined by a roboticist named Masahiro Mori in 1970.
Robots don’t necessarily need a humanlike appearance for humans to relate to them. Ruina pointed to “Luxo Jr.,” the childlike hopping lamp that appears as part of the Pixar logo, as an example of a clearly nonhuman object that still displays humanlike characteristics and creates an emotional connection with human viewers.
But studies have shown that humanlike features — whether they be characteristic, such as the lamp’s behavior, or physical, such as facial expressions — do facilitate an emotional connection. “People responded more positively to an artifact [such as a robot] that displayed humanlike behavioral characteristics…in contrast to a purely functional design,” said Julia Fink of the École Polytechnique Fédérale de Lausanne in a 2012 paper.
Users’ comfort is a good enough reason as any to design robots in a humanlike shape. But Ruina sees an appeal from the roboticists’ perspective as well.
“Why do we make human-shaped robots?” Ruina mused. “Because it’s sort of fun. …It’s like Mount Everest: people just naturally want to climb it.”