Six same-sized bowls---three red and three yellow---are placed on the table:
one red and one yellow at fixed positions near the robot, and the other two red and two yellow in a row farther away.
The robot stacks the two far bowls of the instructed color onto the near bowl of that color.
A trial is successful when both far bowls of the instructed color are stacked on the matching near bowl.
As the bowls differ only in color, the task isolates instruction-conditioned instance selection.