Extended Data Fig. 3: An example in which the context-dependence of syllable acoustics before complex transitions is too small for clear distinction.

a, Same as Fig. 1b. A summary of all phrase sequences that contain a common transition reveals that the choice of what to sing after the pink phrase depends on the phrases that were produced earlier. Lines represent phrase identity and duration. Song sequences are stacked (vertical axis) sorted by the identity of the first phrase, the identity of the last phrase, and then the duration of the centre phrases. b, The discriminability (d′, x axis) measures the acoustic distance between pairs of syllable classes in units of the within-class standard deviation (see Methods). Bars show the histogram across all pairs of syllables identified by human observers (see Methods), corresponding to about 99% or more identification success (Extended Data Fig. 1b). The pink ticks mark the d′ values for six within-class comparison of the main four contexts in a. The orange tick marks the d′ for another context comparison in a different syllable that precedes a complex transition for this bird. c, The pairwise comparison of distributions matching the pink ticks in b. Each inset shows overlays of two distributions marked by contours at the 0.1 and 0.5 values of the peak and coloured according to context in a. The distributions are projected onto the two leading principle components of the acoustic features (see Methods, in the space defined by eight acoustic features⁴⁸). While some of these distributions are statistically distinct, they allow for only about 70% context identification success in the most distinct case.