Nuancing 'Emotional' Social Play: Does Play Behaviour Always Underlie a Positive Emotional State?

Abstract

This review focuses on social play, a complex behaviour that is often difficult to categorize. Although play has been typically associated with positive emotional states, a thorough examination of the literature indicates that it may relate to different emotional systems, from attachment to conflict. Play oscillates between competition and cooperation, and includes a spectrum in between; thus, quantitatively identifying and demonstrating the emotional nature of play remains challenging. We considered examples from human and non-human animal studies and explored the emotional and neuro-hormonal systems involved in play. We assessed ethological data possibly indicating the emotional states underlying play, and we focused on the cooperative and competitive elements of play. We investigated the relationship between play and affiliative/aggressive behaviours, the communicative meaning of play signals (especially primate play faces), and the motor and possibly emotional contagion function of rapid motor mimicry during play. From all the literature on play, this review selects and combines studies in an innovative way to present the methods (e.g., play indices and social network analysis), tools (e.g., sequential analysis and facial coding software), and evidence indicative of the emotional states underlying play, which is much more complex than previously thought.

Keywords: aggressive play; competition; cooperation; play signals; positive/negative emotional states; rapid motor mimicry.

Figure 1

Sequence of play patterns during a playful interaction between immature African forest elephants (Loxodonta cyclotis) in the National Park of Dzanga-Sangha (Central African Republic). Screenshot: Giada Cordoni. Edited by Giada Cordoni.

Figure 2

Graph summarizing the relationships between social play and neural pathways, hormones, and neurotransmitters associated with it. Graph by Ivan Norscia.

Figure 3

An example of a play bow, a typical play signal in canids. The dog (Canis lupus familiaris) crouches on its forelimbs, remains standing on its hind legs, wags its tail, and sometimes barks [80,94,95]. Personal photo by Giada Cordoni.

Figure 4

An example of the play trunk periscope (indicated by the yellow arrow), a play marker in elephant play. An elephant pauses and approaches a group mate with the trunk held up in a periscope or S-shape position [37,96]. The National Park of Dzanga-Sangha (Central African Republic). Edited by Giada Cordoni.

Figure 5

Pictures illustrating the two variants of the open mouth display (indicated by the blue arrows) performed during play in many non-human primates: (A) play face (PF), in which the mouth is opened and lower teeth are exposed, and (B) full play face (FPF), in which the mouth is opened and both lower and upper teeth are exposed. The group of bonobos (Pan paniscus) housed at La Vallée des Singes (Romagne, France). Photo by Giada Cordoni.

Figure 6

An example of rapid facial mimicry (RFM) between chimpanzees (Pan troglodytes) during a play fighting interaction. The exact same facial expression emitted by the trigger T (first stimulus) is replicated by the responder R within 1 s after the emission of the first stimulus (see the red arrow) [119]. Screenshot Giada Cordoni. Edited by Giada Cordoni.