Figure 2. Mean (±sem) number of distress calls produced by piglets during isolation tests where human voices were broadcast according to their prenatal experience (V: prenatal experience of human voice: V1 and V2, N_a = 75 and N_b = 40; C: control without prenatal experience, N_a = 35 and N_b = 20).

(a) Social isolation test at 2 days of age (SIT1) with broadcast of V1 and V2, and (b). social isolation test at 14 days of age (SIT3) with broadcast of V3 and V4 (novel human voices never heard by sows and piglets). Note that similar patterns are observed in the two situations with fewer distress calls in the experimental piglets when hearing any human voice but that this is more marked when the voices had been broadcast before birth.