The cat's intellectual ability is highlighted by its ability to use the information retained to solve problems. Cats are able to form "learning sets," a skill once thought to be confined to primates. For example, cats that were trained to pull boxes on wheels showed they could combine that skill with their own insight to solve new problems. In one instance, a cat pulled the box to a specific location and used it, step-stool fashion, to reach a desired reward: a piece of food suspended from the ceiling by a string. The full extent of the cat's cognitive abilities is still largely unknown, but they continue to amaze their owners with their ingenious abilities, nevertheless.