Domestic cats like boxes because they provide a sense of security. My theory is that domestic cats like the feeling of pressure of the box on their back and sides which is a throwback to when they were newborn kittens at their mother’s breast pushed together with their siblings. That moment was a good moment and a pleasant one. Being inside a box brings back those memories and therefore they feel relaxed and secure. This is something they will seek out and often will sleep under these circumstances.
