Final answer:
The author tested the ants' navigational abilities using a rubber sheet and objects of varying mass, such as a grain of sand, a pebble, and a paperweight, to simulate the curvature of space and observe the ants' path alterations.
Step-by-step explanation:
The passage provided does not explicitly detail an experiment involving ants and chocolate, but it does describe experiments to test the ants' ability to navigate when their path is altered by an object's mass. Initially, the ant walks in a straight line across a rubber sheet representing empty space. When a small grain of sand is placed on the sheet, it does not noticeably affect the ant's ability to walk straight. However, when a pebble, which has more mass, is placed, the ant's path is slightly distorted due to the rubber sheet bending. Similarly, when an object with significant mass like a paperweight is introduced, the ant's path is visibly curved as it is forced down into the sag caused by the paperweight before it can continue on an unaltered part of the sheet.