Abstract: Social observational learning is one of learning abilities expected in domestic horses (Equus caballus) because of their ecological and evolutional history. However, a few studies on this type of learning in horses failed to provide clear evidence of observational learning and/or could not distinguished it from other types of learning. We tested interspecific observational learning abilities using the spatial task and a human demonstrator. We hypothesised that 1) horses with possibility of observing a human demonstrator will complete the task in shorter time than control horses without any demonstrator, and 2) horses observing a familiar demonstrator will carry out the task in shorter time than horses with an unfamiliar demonstrator due to established positive human-horse relationship. We randomly allocated 24 riding horses of mixed age and breed to three groups per 8 and started the task either with observing a familiar demonstrator, unfamiliar demonstrator or without demonstrator (control group). Each horse was released individually at the starting point in the experimental paddock and the latency to pass the task was recorded. A horse completed the task once it walked 25 m from the starting point to the squared area (4x4 m) fenced by a tape, went into it through the entrance on the opposite side and touched the bucket with food. Eight people served as demonstrators, each for one familiar and one unfamiliar horse. Horses from groups with a demonstrator, either familiar or unfamiliar, reached the food bucket significantly faster than control horses during the first trial (mean±SE: 29.1±3.13 s with familiar, 28.9±3.13 s unfamiliar and 41.5 ± 3.13 s without demonstrator, P<0.02, GLMM, PROC MIXED, SAS). Horses did not differ in time needed to reach the fence of the squared area, but in “solving time”, i.e. time from reaching the fence of the squared area and touching the bucket (14.6±2.34, 14.3±2.34 and 27.6±2.34 s in horses with familiar, unfamiliar or without demonstrator, P<0.001). Despite our presumption, the horses observing a familiar demonstrator finished the task in comparable time as horses with an unfamiliar demonstrator (P=0.85) which indicated little effect of long lasting positive relationship between a horse and a particular human. We found, however, large individual variability in performance of individual demonstrators. Further, horses did not differ in time needed to pass the same task without a demonstrator repeated either shortly or 7 days after the first test which supported that interspecific observational learning rather than social facilitation occurred. In conclusion, horses with a human demonstrator, regardless familiar or unfamiliar, were able to solve the task in shorter time compared to control horses but they did not differ in performing repeated task if they learned it by individual or social learning process. This indicates that interspecific observational learning does occur in horses. Supported by AWIN, EU FP7 project No. 266213.

Abstract: Summary For humans, facial expressions are important social signals, and how we perceive specific individuals may be influenced by subtle emotional cues that they have given us in past encounters. A wide range of animal species are also capable of discriminating the emotions of others through facial expressions [1, 2, 3, 4, 5], and it is clear that remembering emotional experiences with specific individuals could have clear benefits for social bonding and aggression avoidance when these individuals are encountered again. Although there is evidence that non-human animals are capable of remembering the identity of individuals who have directly harmed them [6, 7], it is not known whether animals can form lasting memories of specific individuals simply by observing subtle emotional expressions that they exhibit on their faces. Here we conducted controlled experiments in which domestic horses were presented with a photograph of an angry or happy human face and several hours later saw the person who had given the expression in a neutral state. Short-term exposure to the facial expression was enough to generate clear differences in subsequent responses to that individual (but not to a different mismatched person), consistent with the past angry expression having been perceived negatively and the happy expression positively. Both humans were blind to the photograph that the horses had seen. Our results provide clear evidence that some non-human animals can effectively eavesdrop on the emotional state cues that humans reveal on a moment-to-moment basis, using their memory of these to guide future interactions with particular individuals.