Table 2.

Description of the heterospecific play (tickling) behaviours scored.

behaviour	description
playful
nape	when, following an approach or pounce, the rat moves toward the experimenter's wrist or upper palm and nuzzles these areas with its snout
naped	when the experimenter uses their thumb and index finger to rub the nape of the rat's neck and then flips it onto its back
follow	when the rat follows the experimenter's hand around the enclosure
pin	when the rat stands on the fingers and palm of the experimenter's hand as the experimenter tickles the rat's ventral surface, as the rat lays on its back
pinned	when experimenter places their fingers on top of the rat's ventral surface, moving their fingers in a tickling motion
evade	when the rat protects against contact on its nape by dodging, running or jumping away
tickle ventral	when, following nape contact, the experimenter tickles the standing rat's ventral surface [31]
tickle dorsal	when the experimenter tickles the rat's dorsal surface especially its neck [31]
tickle double	when the experimenter tickles the rat on its dorso-lateral surfaces, using both hands
non-playful
approach	when the rat moves towards the hand, but without any clear indication that the wrist is being targeted
solo	when the rat is not interacting with the experimenter's hand
sniff	when the rat sniffs the experimenter's hand
other	when the rat is not engaging with the experimenter's hand and is exploring the side of the enclosure