Cats often lick each other, a behavior called allogrooming, which can be more complex than it appears. While some people assume this action is a sign of friendship, research shows it may have multiple purposes. In a multi-cat household, it's common to see one cat licking another, but the reasons for this behavior can vary depending on the situation and the relationship between the cats. Historically, scientists thought allogrooming helped cats form and maintain social bonds, possibly by creating a shared scent. However, a 1998 study of 25 cats in an enclosed environment found that about a third of the grooming sessions were accompanied by aggressive behaviors, suggesting that allogrooming might also serve to ease tension in close quarters where actual fights could be dangerous. More recent research by Morgane Van Belle, a cat behavior scientist at Ghent University, and her team analyzed allogrooming in 53 two-cat households. They found that the behavior could serve different social functions. When cats licked each other while huddling and mimicking each other's body postures, it likely strengthened their bond. Licking around the ears, which are rich in sensory nerves, might also help the cats relax. Similar calming effects have been observed in other animals, such as horses and monkeys. However, not all instances of allogrooming were peaceful. In some cases, it led to playful wrestling, suggesting it could be a way to initiate play. In other situations, it was followed by signs of conflict, such as flattened ears or pawing. The researchers suggest that allogrooming might act as a way to defuse tension, especially when one cat wants to claim a space or resource from another. This behavior is similar to how subordinate animals in other species, like meerkats, groom dominant ones to avoid conflict. In addition to social functions, allogrooming might help with hygiene. Cats often groom areas like the head and neck, which are hard to reach during self-grooming. Similar behaviors are seen in other animals, like ants and primates, which groom each other to maintain cleanliness. However, more research is needed to determine whether allogrooming in cats actually helps reduce dirt or parasites. Dr. Terry Curtis, a veterinary behaviorist, suggests that feral cats, which may carry more fleas, might groom differently. While the current findings are plausible, she notes that understanding cat behavior is complex and often uncertain. After 25 years of studying animal behavior, she acknowledges that the inner thoughts of a cat may remain a mystery. "Congratulations, you got a cat," she said. "Let the mystery begin."