Does preferential visual hemifield use allow inferring the emotional state of birds? The examples of Quails and Ravens

The understanding of what animals think has been one of the great human dreams since the ancient times. The legend wants that King Salomon was able to understand the animal minds thanks to a magical ring that allowed him to speak with them. Unfortunately, at present nobody has a similar ring but some people are better than others at predicting the behaviour and the emotional state of animals and this ability is based on the perception, nearly always unconscious, of specific signals coming from the animals. The description and the understanding of the neural mechanisms that are responsible for these signals allows to infer the emotional state of an “avian patient” and to understand in which category (familiar/known or foreign/unknown) the animal place the observer. This study analyzes the preferential uses of the right or the left visual hemifield in the quail (Coturnix japonica) and in the raven (Corvus corax), by means of a social recognition paradigm (familiar vs foreign). Our hypothesis was that if responses to familiar and unfamiliar conspecifics differ in the two hemispheres, then the preferential uses of one hemifield to observe the target in the test should vary accordingly. In contrast, if the lateral bias simply reflects a turning preference, irrespective of any social discrimination, then no changes in the direction of bias would be expected. The results for quails and the preliminary results for ravens revealed that the preferential uses of one visual hemifield was clearly affected by the type of stimulus visible in the test (familiar vs foreign). In fact, quails tended to use the lateral (monocular) field of the right eye when viewing a stranger and the lateral field of the left eye when viewing a companion and ravens seems to show the same preferential bias using the left visual hemifield to scrutinize a familiar stimulus.