Word Problems K9What is the main difference between the pictures on the left page and on the right page?

The problem is similar to 100 Bongard Problems on visual pattern recognition.

M. Bongard (1924 – 1971) was a Russian computer scientist. His tests played an important role in the disciplines of cognitive psychology and cognitive science. Bongard died in 1971 during a hiking expedition in the Pamir Mountains.