Figure 5. Analysis of the duration and frequency of flat syllables across ages.
(A) The most typical flat syllable at each age. (B) Distributions of durations of the flat syllable at each age. Older pups are progressively less likely to produce longer flat syllables. (C) Distributions of the dominant frequency of the flat syllables at each age. At p5, p7 and p9 there are two clear peaks in the distribution, but by p11 there are fewer low frequency syllables. The frequency of the higher peak gradually reduces with age. (D) The kurtosis of the duration distribution gets more positive with age, indicating a more peaked distribution of duration. Bars represent the standard error of the mean. (E) Scatter plots of duration against frequency for flat syllables from animals aged p7 and adults. Although there is some overlap, the frequencies of adult syllables fall between those of the pup syllables.