Rats are social animals. They love sleeping in piles, squabbling over crumbs with their cage mates and wrestling together playfully. Your pet may be happiest with other rats, even though most rats are "people pleasers." They learn to trust humans and actively seek out the attentions of their owners. This tendency sets rats apart from other small mammals such as hamsters, which seem to tolerate rather than enjoy human company.
To learn more, read Understanding Your Rat.