Biology subjects

Tomonaga, M.

Publications and source records attributed to Tomonaga, M..

4 recordsLinked to original sources

bioRxiv2018

Effect of visual cues in addition to moderate auditory cues on temporal coordination: A comparative study in humans and chimpanzees

Our previous studies reported that chimpanzees share an ability to produce spontaneous temporal coordination with humans (Yu & Tomonaga, 2015; 2016). However, it remains unclear how visual cues of an interacting partners movement influence on the emergence of tempo convergence. The current study conducted a comparative study in humans and chimpanzees under the same experimental setup as that used in Yu & Tomonaga (2016). Three conditions, including baseline, paired-invisible and paired-visible, were prepared. In the baseline condition, the participants produced the repetitive tapping movement alone. In contrast, in the other two paired conditions, the participants in a pair produced the tapping movement concurrently while facing a conspecific partner. However, in the paired-invisible condition, a visual barrier was placed in between the participants to control visual cues of an interacting partners movement. Moderate auditory cues, corresponding to each participants tapping movement, were presented throughout the conditions. Results showed that there are significant changes on the tapping tempo between baseline and the paired-invisible condition, whereas there are little changes between paired-invisible and paired-visible condition in both species. The current stepwise analysis across three conditions demonstrates that auditory cues were more influential than additive visual cues of an interacting partners movement on the tempo convergence in humans and chimpanzees.

animal behavior and cognition↗

bioRxiv2018

Chimpanzees but not orangutans display aversive reactions toward their partner receiving a superior reward

Fairness judgment is a fundamental aspect of human cooperation. By carefully balancing the payoffs and efforts with cooperating partner (s) we could either avoid or punish cheaters and stably maintain cooperation. Recent studies investigating the origin of this fairness sentiment have demonstrated that this psychological trait is not unique to humans, but also can be observed in other group-living primates, such as chimpanzees and capuchins, suggesting a convergent evolution of a sense of fairness, with cooperative social life being the selective pressure for it. The current study was designed to test this hypothesis by directly comparing the response to the outcome inequity in two of our closest living relatives, chimpanzees and orangutans, having different social systems, i.e. solitary and patrilocal multi-male multi-female groups. Unlike other inequity experiments, we used a prosocial choice apparatus with different reward distributions (advantageous / disadvantageous) to give subjects an active role of not-sharing foods if they considered it unfair. In addition to the choice, we also recorded the behavioral responses of the apes to the inequity. Throughout the experiments aversive emotional responses toward the disadvantageous inequity were only found in chimpanzees, but not in orangutans, supporting the convergent (or domain-specific) evolution of a sense of fairness. However, this aversion to the inequity did not lead the chimpanzees to actually make selfish choices, indirectly supporting the previous findings that chimpanzees employ a partner choice strategy rather than a punishment for fair cooperation. We also found that hierarchy seems to play an important role in the expression of aversion to inequity and prosocial tendency in chimpanzees.

animal behavior and cognition↗

bioRxiv2018

Familiarity and Face-Inversion Effect in Japanese Macaques (Macaca fuscata) during the Preferential Looking Task

Four young laboratory-born Japanese macaques (Macaca fuscata) looked at the photographs of familiar and unfamiliar persons presented at upright and inverted orientations by pressing the lever under the conjugate schedule of sensory reinforcement (successive preferential looking procedure). Three types of photographs were prepared: photographs with persons taken in front view, those taken in back, and those without persons. The monkeys looked longer when the face was upright than inverted only for the pictures containing unfamiliar person with front view. The other types of photographs did not cause inversion effect. Familiarity weakened the face-specific inversion effect in monkeys. This difference may be due to in part the lower preference for familiar faces and the difference in processing mode between familiar and unfamiliar faces.

animal behavior and cognition↗

bioRxiv2018

Inverted Face with Upright Body:Evidence for Face Inversion Effect in Japanese Macaques (Macaca fuscata) under the Preferential Looking Procedure

Young Japanese macaques (Macaca fuscata) looked at the photographs that contained faces of the two species of macaques (M. fuscata and M. mulatta) for longer time when they were presented at upright orientation than inverted orientation, and that species discrimination was deteriorated when the photographs were presented at inverted orientation [16]. The present experiment further explored the factor affecting the inversion effect observed in the previous experiments. Five young laboratory-born Japanese macaques looked at the photographs by pressing the lever under the conjugate schedule of sensory reinforcement, that is, successive preferential looking procedure. Photographs of macaques were scrambled and made up two types of the bizarre photographs: upright face with upright body (orientation consistent) and inverted face with upright body (orientation inconsistent). These two types of photographs were presented at upright and inverted orientations. The monkeys looked longer when the face was upright than inverted. Orientation of body and background had no effect on looking time duration. The present results strongly suggest that inversion effect found in macaques is face-specific.

animal behavior and cognition↗