The social intelligence hypothesis states that the main selection pressures driving increases in brain-to-body ratio are social rather than ecological. The domestic horse is an ideal animal to study within this framework because horses possess rich social lives but inhabit simple ecological environments. Here I assess the abilities of horses within two broad areas of social cognition; the classification of, and the use of information obtained from, social partners.
In Section One I demonstrate that horses are capable of cross-modal individual recognition of conspecifics, an ability not previously demonstrated conclusively outside of humans. This ability extends to identifying familiar human companions suggesting that recognition systems are highly plastic in the individuals they can encode. These results also provide the first insights into the brain mechanisms involved in this process by revealing a clear left hemisphere bias in discriminatory ability.
In Section Two I investigate the extent to which horses are capable of reading human attentional and communicative cues. It has been suggested that this skill was selected for through the process of domestication, however there have been no systematic studies of domestic animals other than the domestic dog. I found that horses were indeed highly
skilled at determining if people were paying attention to them. In contrast they tended to only use basic stimulus enhancement cues to choose a rewarded bucket. A further study of young horses indicated that the ability to detect human attention requires significant experience to develop fully whereas the ability to use stimulus enhancement cues in an object choice task appears to require far less (if any) experience to develop.
Overall my thesis extends our knowledge of comparative social cognition and in particular our knowledge of social cognition in horses. Taken together, these results clearly demonstrate that horses do indeed possess some complex socio-cognitive skills
