Figure 1
Effect of the valence on the vocal parameters. (a) Call duration (Dur), (b) Amplitude modulation rate (AmpModRate), (c) Spectral center of gravity (Q50%) and (d) Wiener entropy (WienEntropy), as a function of the valence (“ − ” = negative (grey); “ + ” = positive (white)) and call type (“LF” = low-frequency calls; “HF” = high-frequency calls). Boxplots: the horizontal line shows the median, the box extends from the lower to the upper quartile and the whiskers to 1.5 times the interquartile range above the upper quartile or below the lower quartile, and open circles indicate outliers and black circles the mean; the grey lines show the model estimates (continuous line) and 95% confidence intervals (dashed lines). All comparisons between negative and positive valence, for each call type, were significant (LMM: p ≤ 0.001).
