Abstract: Keas, a species of parrots from New Zealand, are an interesting species for comparative studies of problem solving and cognition because they are known not only for efficient capacities for object manipulation but also for explorative and playful behaviors. To what extent are they efficient or explorative, and what cognitive abilities do they use? We examined how keas would solve several versions of artificial-fruit box problems having multiple locks. After training keas to remove a metal rod from over a Plexiglas lid that had to be opened, we exposed the birds to a variety of tasks having two or more locks. We also introduced a preview phase during which the keas had extended opportunity to look at the tasks before the experimenter allowed the birds to solve them, to examine whether the preview phase would facilitate the birds' performance on the tasks. In a large number of tests, the keas showed a strong trend to solve the tasks with no positive effect of previewing the tasks. When the tasks became complex, however, the keas corrected inappropriate responses more quickly when they had had chance to preview the problems than when they had not. The results suggest that the keas primarily used explorative strategies in solving the lock problems but might have obtained some information about the tasks before starting to solve them. This may reflect a good compromise of keas' trial-and-error tendency and their good cognitive ability that result from a selection pressure they have faced in their natural habitat.

Abstract: An important question in the study of animal communication is whether non-human animals are able to produce communicative gestures, i.e. nonvocal bodily actions directed to a recipient, physically ineffective but with a meaning shared in the social group [1]. Passive gestures are instrumental, tuned to the mere presence/absence of others, whereas active informers recognize receivers as communicative agents and activate shared-attention mechanisms for identifying their attentional state (SAM [2]; e.g. Schwab and Huber [3]). Six operational criteria must be evaluated to classify a signal as referential and intentional [4]: (1) alternative gazes between the partner and the target; (2) apparent attention-getting behaviours are deployed; (3) an audience is required to exhibit the behaviour; (4) the attentional status of an observer influences the propensity to exhibit behaviours; (5) communication is persistent and (6) there is elaboration of communicative behaviour when apparent attempts to manipulate the partner fail. Dogs [5] and non-human primates (reviewed in Liebal and Call [6]) can tune a human receiver’s attention to the object of interest by combining directional and attention-getting signals, such as turning the head or body, gazing to the receiver, and/or establishing eye contact. Research on other species is scarce.
Horses rely on humans to survive in domestic settings and may have evolved skills for communicating flexibly with them [7]. Horses understand human attentional cues (such as body and head orientation, eyes opened/closed) [8], permanent pointing [9] and, to some extent, gazing [10]. Here we tested the ability of 14 outdoor, herd-living domestic horses to communicate referentially with a human partner about the location of a desired target, a bucket of food out of reach. After the baiting of two buckets placed in opposite, unreachable locations were shown by the experimenter, the subject would walk to one of the two buckets. Because approaching a bucket would reveal that the food is out of reach, we expected the horse to look back to the experimenter, then to the bucket, and alternate this gazing several times to indicate its intention. To test whether our prediction is correct and alternate gazing is indeed the result of the horse's referential communication, we video-recorded the behaviour of the subjects in the test (FORWARD) and three control conditions: (1) FORWARD: experimenter oriented to the center of the arena, (2) BACK: experimenter backward oriented in respect to the arena, (3) ALONE: experimenter absent, (4) MANY: as FORWARD plus a familiar human oriented to the subject behind the bucket (Figure 1). We used a conservative criterion of back gazing by considering only turning the head back more than 90 degrees. The results confirmed our prediction. The horses alternated gazes between the partner and the buck significantly more often in the FORWARD than in all the other conditions (Table 1), thus satisfying operational criteria #1, #3 and #4. They also alternated head nods with gazes to the partner significantly more often during the FORWARD condition. We thus considered head nods not an instrumental signal of arousal, but an attention-getting behaviour with communicative function. Subjects used both head nods and neck stretched toward the buck more often in the FORWARD than in the BACK and the ALONE conditions, thus satisfying criteria #2, #3 and #4. In condition MANY, the frequency of head nods did not differ from condition FORWARD, probably because nods were directed to the additional partner behind the buck. This also satisfies criteria #4. The horses gazed to the partner most often in the FORWARD than in the BACK and the MANY conditions, but not in the ALONE. In this condition, subjects could observe the partner walking further from the test arena. To test for the different functions of gazes in presence and in absence of the partner, we compared their average duration between the two conditions: the significantly longer duration of gazes when the subject was alone suggests the instrumental monitoring function of gazes in this experimental condition.
Altogether, the findings suggest that domestic horses possess the ability to use referential communication in an interspecific context, but additional analyses are needed to test for operational criteria #5 and #6. Flexible and voluntary use of communicative signals reveal sophisticated cognitive processes involved in the strategic emission of these signals, and the finding of referential communication skills in an ungulate species forces us to reconsider the evolutionary path of intelligence. Furthermore, ungulates are used intensively by humans (transportation, meat, agriculture, leisure activities), and their welfare is often compromised. Determining whether ungulates can communicate their needs and preferences is paramount to a proper ethical management.

Abstract: Referential communication occurs when a sender elaborates its gestures to direct the attention of a recipient to its role in pursuit of the desired goal, e.g. by pointing or showing an object, thereby informing the recipient what it wants. If the gesture is successful, the sender and the recipient focus their attention simultaneously on a third entity, the target. Here we investigated the ability of domestic horses (Equus caballus) to communicate referentially with a human observer about the location of a desired target, a bucket of food out of reach. In order to test six operational criteria of referential communication, we manipulated the recipient’s (experimenter) attentional state in four experimental conditions: frontally oriented, backward oriented, walking away from the arena and frontally oriented with other helpers present in the arena. The rate of gaze alternation was higher in the frontally oriented condition than in all the others. The horses appeared to use both indicative (pointing) and non-indicative (nods and shakes) head gestures in the relevant test conditions. Horses also elaborated their communication by switching from a visual to a tactile signal and demonstrated perseverance in their communication. The results of the tests revealed that horses used referential gestures to manipulate the attention of a human recipient so to obtain an unreachable resource. These are the first such findings in an ungulate species.