Cat-cat visual, olfactory and auditory communication have been fairly well deciphered beginning with Leyhausen's (14) original work on the body and facial signals used [expanded by (15–17)]. Cats often use some of the same visual and vocal signals when interacting with people. When they approach another familiar cat and greet their keepers after a short absence, they raise their tails upright, presumably as a sign of friendly intentions. Only domesticated cats use this signal and it has been suggested that there was selective pressure for such a signal in the dense temple colonies of ancient Egypt (18). To get our attention, they flank-rub on our legs (which might also mark us) and head-rub—forehead to forehead—with cats they know well, presumably marking each other (and us) with a scent (1, 19). Bernstein and Friedmann [(20), also citing (21)] reported that cats preferred certain places on their bodies, particularly the head region, for being stroked, modified their postures to promote access to those preferred regions, and even led their keepers to preferred places in the home for petting episodes. Ellis et al. (22) determined that both handler familiarity and body region stroked significantly influenced negative behavioral responses. Bernstein and Friedmann (op cit.) also mentioned the cat's closing of the eyes in this relaxed situation (sometimes called the “slow blink”). This slow-blink has received more attention recently and when previously unfamiliar persons initiate such blinking, cats tend to approach them more often (23).

Auditory communication by cats has been and continues to be examined [reviewed by (17)], most recently by Schötz et al. (24) using phonetic analyses of cat-to-human vocalizations. It is generally known that cats vocalize more frequently with their human companions than with other cats (1). Yeon et al. (25) found that meows are attention-seeking vocalizations in interspecific situations and higher pitched (subjectively more pleasant) than in feral cats and wild ancestors. They also modify their purrs when actively soliciting food (more urgent and less pleasant than when just resting as perceived by the human raters) and people are capable of distinguishing these (26), both behaviors probably learned over time in interactions. Ellis et al. (27) reported that 40% of their human participants identified the correct contexts of cat vocalizations more often than by chance when the vocalizations belonged to their own cat, but did not perform above chance when the calls belonged to an unfamiliar cat. Interestingly, Saito et al. (28) demonstrated with the habituation-dishabituation method that privately owned cats can discriminate their own names from other words, which leads now to other studies in the area of social cognition in cats.

Recent work on social cognition in cats also has relevance to cat-human communication. Vitale Shreve and Udell (29) provided a first review of what was known and still to be discovered and a number of studies have since been published. Pongracz and his colleagues in Hungary have been particularly active this this area. Even though Miklosi et al. (30) had already shown differences between dogs and cats in their ability to use human pointing gestures, especially that cats lacked some components of attention-getting behavior compared with dogs, Pongracz et al. (31) demonstrated that cats were indeed able to read and follow human gaze for referential information. Galvan and Vonk (32) found that cats were only modestly sensitive to emotions as indicated by human postural and vocal cues, but particularly when displayed by their owner. Quaranta et al. (33) demonstrated experimentally that cats are indeed capable to cross-modally match pictures of emotional faces with their related vocalizations in both conspecifics and humans, especially for high intensity emotions. These authors concluded that cats have a general mental representation for the emotions of their social partners, both conspecific and human.

Rieger and Turner (42) and Turner and Rieger (43) discovered that not only the mere presence of a cat in the household, but also interactions with the cat reduce measureable negative moods in the person, e.g., anxiety, depression, and introversion. The depressive owner initiates fewer interactions with the cat, but when the cat approaches that person, s/he accepts the intent of the cat to interact, which affects the human's mood. The cat also changes its behavior in response to depressiveness of the human when close to the person (but not at a distance), vocalizing more frequently with the person and head- and flank-rubbing more often on that person. More mood subscales in women than in men are affected by the cat, and they are more strongly affected than in men. Turner et al. (44) concluded that only the partner, but not the cat, enhances positive moods, while the cats alleviate negative moods. This effect was comparable to the effect of a human partner.

The team's recently-published study explored the five different types of relationships cats develop with their owners: Pets and pet parents will develop an open relationship, a co-dependent relationship, a casual relationship, a friendship, or a remote relationship.

Research has shown that cats can provide emotional support, improve moods, and contribute to the overall morale of their owners. Cats are also credited with promoting socialization among older individuals and physically or mentally disabled people. Nearly 40 million households in the United States have pet cats.