Figure 3.

Syllable variability was greater in birds with larger numbers of new HVC neurons. Similarity scores for motifs sung on the day before perfusion (a measure of within-day variability in syllable structure) was significantly correlated with new neuron numbers (r = −0.605; n = 20; p = 0.0047). Note that lower similarity indicates higher variability. This effect was not driven by differences between controls and isolates: adding the group membership variable did not change the significance of the relationship between syllable similarity and new neuron number (stepwise multiple regression).