Metacognition in nonhuman primates: a review of current knowledge.

Metacognition, the ability to monitor and control one's own cognitive processes, has long been considered a hallmark of human cognition. However, two decades of research have provided compelling evidence of metacognitive-like abilities in some nonhuman primates. This review synthesizes current knowledge on the subject, highlighting key experimental paradigms and empirical findings, with an emphasis on the latest studies.

Metacognition in Japanese macaques (Macaca fuscata): does impulsivity explain unnecessary looks in the tubes task?

Potential metacognitive abilities, such as monitoring and controlling cognitive processes, have been revealed in some primate species. In the tubes task, apes and macaques showed higher content-checking behavior when unaware of a reward's location, but they also periodically inspected the tubes when aware, especially when a more appealing reward was involved. Some attribute this to the pleasure of looking at the reward.

Metacognition in wild Japanese macaques: cost and stakes influencing information-seeking behavior.

Metacognition allows us to evaluate memories and knowledge, thus enabling us to distinguish between what we know and what we do not. Studies have shown that species other than humans may possess similar abilities. However, the number of species tested was limited.

Examination of the joint Simon effect in rats: Changes in task performance based on actions of the partner.

Nonhuman animals have demonstrated various cooperative behaviors; however, many examples can be interpreted as individual contributions to a task rather than true behavioral coordination. In this study, we used the joint Simon task in rats to determine whether the presence of and task sharing with a partner affected performance in a joint activity. Rats were trained to discriminate between two auditory stimuli (3 and 12 kHz tones) and individually performed an auditory Simon task.

An exploratory study of behavioral traits and the establishment of social relationships in female laboratory rats.

There is growing evidence that social relationships influence individual fitness through various effects. Clarifying individual differences in social interaction patterns and determinants for such differences will lead to better understanding of sociality and its fitness consequences for animals. Behavioral traits are considered one of the determining factors of social interaction.

Stimulus modality affects the accuracy of rhythm production in rats.

Vocal learning species such as humans and parrots show auditory dominance when they synchronize their actions to an external rhythm. However, whether non-vocal-learners show a specific modality dominance in a rhythmic task has scarcely been examined. We predicted that rats, who are nocturnal and known to rely on acoustic communication, would exhibit higher sensitivity to auditory rhythm compared to visual rhythm.

Production of regular rhythm induced by external stimuli in rats.

Rhythmic ability is important for locomotion, communication, and coordination between group members during the daily life of animals. We aimed to examine the rhythm perception and production abilities in rats within the range of a subsecond to a few seconds. We trained rats to respond to audio-visual stimuli presented in regular, isochronous rhythms at six time-intervals (0.

Temporal adjustment of short calls according to a partner during vocal turn-taking in Japanese macaques.

Turn-taking is a common feature in human speech, and is also seen in the communication of other primate species. However, evidence of turn-taking in vocal exchanges within a short time frame is still scarce in nonhuman primates. This study investigated whether dynamic adjustment during turn-taking in short calls exists in Japanese macaques We observed exchanges of short calls such as grunts, girneys, and short, low coos during social interactions in a free-ranging group of Japanese macaques.

Vocalizations during post-conflict affiliations from victims toward aggressors based on uncertainty in Japanese macaques.

We investigated the use of vocalizations called "grunts," "girneys," and "coos" accompanied by post-conflict affiliative interaction between former opponents (reconciliation) in Japanese macaques (Macaca fuscata). Although reconciliation functions to repair bonds, such interactions sometimes entail risks of receiving further aggression. Vocalizations can be used at a distance from the former opponent; thus, we predict that vocalizations are used particularly by victims of a conflict, and are frequently used in situations of uncertainty when it is difficult for them to estimate whether the former opponent will resume aggression.

Social relationships of nulliparous young adult females beyond the ordinary age of the first birth in a free-ranging troop of Japanese macaques (Macaca fuscata).

We describe the social relationships of young adult female Japanese macaques (Macaca fuscata) in a free-ranging troop in Arashiyama, Kyoto, Japan, who remained nulliparous beyond the ordinary age of first birth because of contraceptive administration. We observed 12 young nulliparous adult females (6-9 years old) for 270 h and 10 min from 2 February to 5 October 2010. The majority maintained close relationships with their mothers through proximity and grooming, whereas a few had very infrequent social interactions with their mothers.