Abstract: Dogs are known to consistently follow human pointing gestures. In this study, we asked whether dogs “automatically” do this or whether they flexibly adjust their behavior depending upon the reliability of the pointer, demonstrated in an immediately preceding event. We tested pet dogs in a version of the object choice task in which a piece of food was hidden in one of the two containers. In Experiment 1, Phase 1, an experimenter pointed at the baited container; the second container was empty. In Phase 2, after showing the contents of both containers to the dogs, the experimenter pointed at the empty container. In Phase 3, the procedure was exactly as in Phase 1. We compared the dogs’ responses to the experimenter’s pointing gestures in Phases 1 and 3. Most dogs followed pointing in Phase 1, but many fewer did so in Phase 3. In Experiment 2, dogs followed a new experimenter’s pointing in Phase 3 following replication of procedures of Phases 1 and 2 in Experiment 1. This ruled out the possibility that dogs simply lost motivation to participate in the task in later phases. These results suggest that not only dogs are highly skilled at understanding human pointing gestures, but also they make inferences about the reliability of a human who presents cues and consequently modify their behavior flexibly depending on the inference.

Abstract: It is advantageous to identify individuals who are likely to behave fairly and those who are not. This ability to judge others’ fairness seems important for social species to interact or cooperate with their partners. Domestic horses (Equus caballus) have lived with humans for over five thousand years, hence they might have developed sensitivity to human personality. In the present study, we investigated whether horses would discriminate between a person who behaved fairly and a person who behaved unfairly. Specifically, we asked whether horses show a preference for the former. We tested 12 horses (11 thoroughbred and 1 Anglo-Arabian horses) at the horseback-riding club of Kyoto University. They were divided into 6 pairs which consisted of a participant and a partner. A participant was picketed between two polls next to a partner at the hoof washing place. Each horse put his/her mouth in an actor’s hand when the actor (an unfamiliar person) stood in front of them, and then received food from the actor. A fair actor always behaved fairly and gave a small quantity of hay (low-value food) to both of them in return for the task. An unfair actor always behaved unfairly, giving a small quantity of hay to the participant in return for the task, but always giving a piece of carrot (high-value food) to the partner in return for the task. Both actors always stood in front of the partner first, so the partner always did the task and received food from the actor before the participant. Finally, the participant was offered a piece of carrot by the two actors. The participant indicated which offer was accepted by stretching toward the chosen actor. The latter then moved the hand forward to allow the participant to take the food while the other actor’s hand withdrew. The orders (1st or 2nd) and the positions (left or right) of the two actors varied pseudo-randomly across trials. The color of the clothes of the two actors (white or black) was counterbalanced between sessions. We conducted 8 sessions, consisting of 8 experimental trials, across which the actors maintained their respective roles (fair or unfair) of the fair and unfair person. Furthermore, the two actors switched roles across sessions so that they played both roles the same number of times. One session was run per day. If horses can discriminate between fair and unfair people and show a preference for the former, they should choose the former significantly more often than the latter when both actors offered food. The participants showed no overall preference for accepting food from either actor. However, three of six participants showed a side preference. The result of the present study suggests that horses are insensitive to humans’ fairness. Horses may not have expectations about fair treatment.

Abstract: Human infants perceive two rods moving in concert behind an occluder as one unitary rod. In four experiments we tested whether pigeons also perceive unity of objects. Pigeons were trained on a matching-to-sample task to discriminate between one unitary rod moving at a constant speed and two aligned rods moving together at the same speed. The latter stimulus was identical to the former except for a gap in the center. In experiment 1, we tested pigeons in probe trials in which a rectangle occluded the center of the sample rods, to see which comparison stimulus, the unitary rod or the aligned two rods, the subjects would match to the sample. Two of the three subjects pecked at the two rods significantly more often than at the unitary rod. In experiment 2, we trained the same pigeons to match the sample rods moving “in front of” the occluder. Pigeons persisted in matching two separate rods to the unitary rod moving in front of the occluder. In experiments 3 and 4, we used a parallelogram and an undulating shape as the occluder to alter the shape and the size of the portions above and below the occluder by the motion of the sample rods. Both subjects chose the two rods significantly more often than chance in experiment 3 and one of them did so in experiment 4. The results suggest that pigeons do not complete occluded portions even though the two elements move in concert. These negative results suggest that some alternative way of identifying objects may have evolved in pigeons.