Moravec noted that adult-level test scores were fairly easy for computers, while a one-year-old's perception and movement were hard.

A cloth review notes that force on a soft object changes its shape as well as moving it, so the robot must read it again.

Objects get nudged or turn out heavier than expected. The sense, plan, move loop lets the robot notice and adjust.

Pressed against an object, its soft skin dents and stretches. The 2017 paper found it could usually detect sliding and twisting in the grip.