Project on People and Robots: Carnegie Mellon University

Special Topic: How Should a Robot Head be Designed?

How do you design a robot head for research? We designed and fabricated a reconfigurable humanoid robot head that allows us to conduct experiments with a range of facial features and dimensions.

The reconfigurable robot head allows us to pop in and out different face parts and manipulate proportions and spacing creating different robot faces. These faces can then be used as variables in a variety of experiments. On this head both mouth and eyebrows move with robot expression; surface details on these parts can also be changed. For example we may look at the impact of cold silver lips vs soft pink lips on the perception of gender.

Pupil distance and eyeball size can be shifted between 3 variables. This alters the face from a "stern predator" robot with narrow eyes to a "youthful and naive" robot with large wide spread eyes. Finally forehead and jaw pieces of the robot face can be replaced with larger versions manipulating the overall proportions of the face. Combined these variables allow us to create a variety of robot face effects.

What makes a robot head appear human? We discovered important findings related to the presence of features, the total number of features, and the dimensions of the head.

Presence of Features
You might assume that all humanoid robots have facial features, but this is not the case. However, the presence of facial features is very important and figures greatly in our perception of humanness in robot heads. The three features that increase the perception of humanness most are nose, eyelids and mouth.

Several robots demonstrating the presence of no facial features to many facial features. Clockwise from top left: SIG, with no facial features; Pearl, with some facial features; WE-3RV, with several articulated facial features; Lazlo, with facial features but no "skin" or armature.

Total Number of Features
The total number of features on a robot's head is significant in the perception of humanness. The more features a robot head has. the more human-like it will be perceived.

Several robots showing varying numbers of facial features. Clockwise from top left: C3PO; Flo; Kismet; Robonaut.

Dimension of the Head
The proportion of human heads and the distribution of features is fairly similar across cultures and races. However, this is not the case for robots, who have a variety of heads ranging from tall and narrow to squat and wide. The wider the robot head, the more machine-like it is perceived. The taller the robot head, the more human-like it is perceived.

A range of robot heads illustrating proportions from wide to tall. Clockwise from top left: Asimo, a nearly round robot head; DB, with a head that is wider than it is tall; PaPeRo, with a head that is taller than it is wide; WAMOEBA, with a nearly round head.

To learn more about how we designed a new humanoid robot head for Pearl, please take a look at [link to study page] and [link to pdf file].

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