Social visual contact, a primary "drive" for social animals?

Social animals are always searching for conspecifics, thereby expressing a genuine "social need". This need is illustrated by the fact that social isolation can induce isolation syndromes that can be attenuated by devices such as mirrors. Social contacts appear to be so vital for social animals that they may be ready to work to obtain social stimulations. We used operant conditioning to investigate the possibility to use visual contact (through pictures of conspecifics) as a primary reinforcer. Isolated European starlings (Sturnus vulgaris) were offered the choice of seeing either social images (i.e. pictures of conspecifics) or non-social images (i.e. pictures of landscapes or pictures of monkeys) by triggering sensors. In contrast with most studies, our subjects were presented still pictures of conspecifics and not videos. Moreover, these pictures were used as primary reinforcers and thus were not paired with food. Our data show that starlings were ready to work and to use the apparatus (i.e. sensors) to see pictures in the absence of any other reward. Moreover, they actively and significantly preferred pictures of conspecifics to pictures of inanimate objects (landscapes) or of heterospecifics (monkeys). This suggests that 2D pictures with a social overtone can be used as primary reinforcers for isolated social birds.