A review of interspecific social play among nonhuman animals

Monkey-deer rodeo: exploring the mounting behaviours of Japanese macaques (Macaca fuscata) on Sika deer (Cervus nippon)

Interspecies interactions present diverse forms and functions, contributing significantly to ecological and social dynamics. This study focuses on the mounting behaviours of Japanese macaques (Macaca fuscata) towards Sika deer (Cervus nippon), a rare and still unexplained phenomenon, with minimal emphasis on the behaviour of the deer. Using video data from two distinct sites, Yakushima and Minoh, Japan, we documented 45 sequences of macaque-deer interactions and analysed macaques' behaviours and deer behaviours using focal and behavioural sampling techniques. We identified four primary activities performed by macaques during mountings-sexual, play, grooming, and resting-with resting being predominant. The study evaluates six hypotheses regarding the functions of these mounting behaviours: (1) interactions are sex-specific, (2) macaques use deer for transportation, (3) mutual warming through physical contact occurs, (4) deer provide support for resting, (5) macaques engage in grooming to consume parasites or play to strengthen interspecies bonds, and (6) aggressive signals relate to resource disputes or rejection of mounting behaviour. Statistical analyses using the Kruskal-Wallis test and Dunn's post-hoc test revealed significant differences between resting and other active behaviours, but no significant differences in behaviour duration between lying and sitting positions. Adults engaged in mounting for longer periods than juveniles, suggesting potential age-related differences in social and reproductive roles. These findings enhance our understanding of interspecies interactions by focusing on macaque behaviours and emphasise the need for longitudinal studies to clarify the ecological and social implications of these interactions.

Animal play and evolution: Seven timely research issues about enigmatic phenomena

The nature of play in animals has been long debated, but progress is being made in characterizing play and its variants, documenting its distribution across vertebrate and invertebrate taxa, describing its mechanisms and development, and proposing testable theories about its origins, evolution, and adaptive functions. To achieve a deeper understanding of the functions and evolution of play, integrative and conceptual advances are needed in neuroscience, computer modeling, phylogenetics, experimental techniques, behavior development, and inter- and intra-specific variation. The special issue contains papers documenting many of these advances. Here, we describe seven timely areas where further research is needed to understand this still enigmatic class of phenomena more fully. Growing empirical and theoretical evidence reveals that play has been crucial in the evolution of behavior and psychology but has been underestimated, if not ignored, in both empirical and theoretical areas of evolutionary biology and neuroscience. Play research has important ramifications for understanding the evolution of cognition, emotion, and culture, and research on animals can be both informative and transformative.

Play behavior in ectothermic vertebrates

Until a few decades ago, play was considered a behavior unique to birds and mammals. Although play in other vertebrates is still a neglected research subject, data on it has been slowly accumulating, and are reviewed here. Now we know that animals as diverse as stingrays, cichlid fishes, monitor lizards, softshell turtles, and crocodiles can be unexpectedly playful. This knowledge has implications to broader theoretical problems, but much more research attention is needed to utilize its potential.

Autogenous cerebral processes: an invitation to look at the brain from inside out

While external stimulation can reliably trigger neuronal activity, cerebral processes can operate independently from the environment. In this study, we conceptualize autogenous cerebral processes (ACPs) as intrinsic operations of the brain that exist on multiple scales and can influence or shape stimulus responses, behavior, homeostasis, and the physiological state of an organism. We further propose that the field should consider exploring to what extent perception, arousal, behavior, or movement, as well as other cognitive functions previously investigated mainly regarding their stimulus-response dynamics, are ACP-driven.

Play in video games

Video game play is remarkably ubiquitous in today's society given its recent emergence only in the late 1950s. While this fast evolution could exemplify the power of play, video games exploit but also extend other types of play. Here, we review a classification of the ecosystem of video games useful in the emerging field of the cognitive neuroscience of video games. We then discuss how video games may leverage different play types, considering first locomotor-rotational, object, and social play before highlighting the importance of role, rule, and pretend play in video games. With an eye toward comparative studies of the neural bases of play across species, we discuss whether video games may fulfil the five criteria from Burghardt (2005) to identify play. Finally, in line with play's possible preparatory role for adulthood, we review the positive impact on cognition and future learning of action-like video games. Highlighting that not all video games have this impact, we note more granular hypotheses about the biological functions of play are to be encouraged.