Does inattentional blindness exist in horses (Equus caballus)

Abstract Inattentional Blindness (IB) is a phenomenon which has been widely researched in humans. If attention is highly focused, humans may become blind to other environmental cues. To further understand the perception of horses, we applied the well-tested experimental design of human IB studies to the first study of this kind in horses. Since the use of cognitive tasks in human IB-studies ensures that the subject’s attention is focused in a certain direction, we wanted to show if a food reward is strong enough to induce IB in the horse while confronted with a novel object. Therefore, we tested 24 horses, divided in an experimental (n = 12) and a control group (n = 12). The horses had to walk through the same corridor (10 m) for 12 consecutive trials. In the experimental group, animals were trained to focus on a food reward presented at the end of the corridor. Their duration to pass the run decreased significantly, indicating that an expectation focused on the feed was induced. In the test trials 11 and 12, a startle stimulus was presented to both groups. The response to the novel object was scored from 1 (no reaction) to 5 (flight reaction). We found a significant difference between the groups in the second test run with the experimental group showing lower reactions to the novel object ( p  =  0.018). The horses in the experimental group where not completely “blind” to the object, but the food reward clearly influenced their reaction. The results of the study suggest that while the occurrence of IB in horses has yet to be proven, a suitable distractor can lower horses’ startle response to a novel object. By further investigation into IB, new insight into the perception of horses can emerge and improve the understanding between horses and their handlers.