Unsure robots make better teachers than know-alls

Douglas Haven, via a kind reader:

The best way to learn is to teach. Now a classroom robot that helps Japanese children learn English has put that old maxim to the test.
Shizuko Matsuzoe and Fumihide Tanaka at the University of Tsukuba, Japan, set up an experiment to find out how different levels of competence in a robot teacher affected children’s success in learning English words for shapes.
They observed how 19 children aged between 4 and 8 interacted with a humanoid Nao robot in a learning game in which each child had to draw the shape that corresponded to an English word such as ‘circle’, ‘square’, ‘crescent’, or ‘heart’.
The researchers operated the robot from a room next to the classroom so that it appeared weak and feeble, and the children were encouraged to take on the role of carers. The robot could then either act as an instructor, drawing the correct shape for the child, or make mistakes and act as if it didn’t know the answer.