Song Practice Promotes Acute Vocal Variability at a Key Stage of Sensorimotor Learning
Figure 5
Sequence variability increases following continuous song practice at 75d.
A) Markov chains for one bird in the two conditions illustrate the probability of syllable transitions observed using the motif-based analysis. Letters denote syllables. Line thickness corresponds to probability; thicker lines indicate greater probabilities. In the NS-UD condition, syllable E transitions to syllable C 83% (thick line) of the time whereas a thinner line represents a 16% probability that E ends the motif. By contrast, in the UD-UD condition, syllable E transitions to syllable C 50% of the time, to syllable D, 43%, and ends the motif 7%. In the NS-UD condition, syllable F occurs infrequently compared to the UD-UD condition. B) Examples of 3 consecutive motifs from the same 75d bird in the NS-UD and UD-UD conditions. Motifs occurred in the same chronological order in the selected 20 motifs analyzed (#11,12,13). Individual syllables are identified by letter. In the NS-UD condition, syllable A typically transitions to itself or to syllable E, and syllable C transitions most frequently to syllable D. By contrast, in the UD-UD condition, A also transitions to C (#13) as well. In the UD-UD condition, syllable F is observed (#11,12,13) and follows syllable D while in NS-UD, syllable D transitions to E (#12) or ends the motif (#11,13). C–D) Paired data scores for the NS-UD (filled circles) and UD-UD (open circles) conditions for each bird are represented by connected lines. At 75d, songs sung in the UD-UD condition exhibited greater variability (*, 2-tailed paired bootstrap ‘Rescaled Entropy’) compared to the NS-UD condition for both the string- (C, p<0.005) and motif-based analysis (D, p<0.05). E) Histogram reveals the percent change in stereotypy between the conditions.