Table 2. Acoustic characterization of the playback categories.
| Human infant | Dog | Chimpanzee | Tree shrew | |
| Agonistic context – negative emotional valence | ||||
| STIM DUR | 0.72±0.18 | 0.85±0.15 | 0.75±0.18 | 0.77±0.13 |
| CALL DUR | 87.54±18.82 | 72.01±20.10 | 100±0 | 59.98±5.15 |
| No. CALL | 1.79±1.32 | 2.58±1.18 | 1±0 | 6.38±1.21 |
| PEAK | 1241.89±738.20 | 773.23±282.51 | 1815.80±444.92 | 5279.18±1164.82 |
| MEAN f0 | 510.73±145.93 | 358.35±224.62 | 1197.87±158.67 | 2341.90±282.48 |
| SD f0 | 81.11±86.05 | 69.48±68.51 | 73.76±49.76 | 194.36±100.96 |
| %VOI | 76.97±25.67 | 42.32±32.38 | 92.83±9.19 | 45.35±11.47 |
| Affiliative context – positive emotional valence | ||||
| STIM DUR | 0.76±0.13 | 0.72±0.16 | 0.82±0.14 | 0.69±0.16 |
| CALL DUR | 88.64±14.28 | 55.34±12.66 | 64.47±10.14 | 54.94±14.51 |
| No. CALL | 2.21±1.41 | 2.29±0.69 | 4.38±1.81 | 5.04±2.10 |
| PEAK | 896.97±731.50 | 312.65±426.50 | 799.56±359.07 | 438.09±1287.29 |
| MEAN f0 | 479.66±323.51 | 493.47±216.22 | - | - |
| SD f0 | 110.28±177.85 | 68.89±49.61 | - | - |
| %VOI | 78.86±19.12 | 39.86±24.35 | 0±0 | 0±0 |
Mean ± standard deviation of following acoustic parameters: STIM DUR = duration of the stimulus (seconds), CALL DUR = percentage of time of the calls in the whole stimulus (%), No. VOC = number of calls in the stimulus; PEAK = peak frequency (Hz), MEAN f0 = mean fundamental frequency (f0, Hz), SD f0 = standard deviation of f0 (Hz), %VOI = percentage of voiced frames in the stimulus (%).