Figure 2.

Behavioural responses to the playbacks. Individual PC1 scores (circles) of the PCA carried out on behavioural responses of mothers to calls of their five-week-old kids (previous kids–playbacks 1; n = 8 mothers), of the same calls played back 11–17 months later (previous kids–playbacks 2; n = 9 mothers) and of calls of familiar kids (familiar kids; n = 9 mothers). Black dots indicate the mean for each treatment. More positive scores correspond to stronger responses (i.e. faster response, higher call rate, longer duration of looks towards the loudspeaker). Mothers tended to respond more to their own kids during playbacks 1 than when the same calls were played back during playbacks 2. They also responded more to their previous kids than to familiar kids during playbacks 2 (linear mixed-effects models).