It's estimated that up to one third of pet cats are kept indoors only, and over fifty percent of cats, that are kept indoors, also spend part of their time outdoors. 

The indoor environment is fairly static and unchanging. This can lead to boredom and stress for the cat. Stress in cats can be manifested by a change in their behavior. The more common behavior problems reported by owners include house soiling (urinating or defecating outside of the litter box), inter-pet problems, and aggression towards humans.

A recent study on cat behavior examined the effect of owner play time with their cat and other environmentally enriching factors. Interesting findings of the study included:

• Female cats are 50% less likely to have reported behavior problems compared to males
• More undesirable behaviors are reported in cats that spend time out of doors and that hunt
• Fewer behavior problems, overall, are seen in cats in which:
• Their owners teach them tricks
• Their owners play with them for more than 5 minutes at a time / play session
• Various toys are provided for them - balls, string toys, and feather toys
• Owners spend time providing massage or petting their cats
• There are other cat companions in the household