Figure 4.

Prolonged exposure of the bird to DAF causes gradual changes in the song. The mean pitch of one of the target song syllable was manipulated by feedback conditional on pitch. Each datapoint is the pitch of the target syllable averaged over all the renditions of the target syllable sung by the bird on a given day. The number of renditions varies from day to day (mean = 208, min = 126, max = 288). Error bars are s.e.m. Dashed lines are the values of the threshold. Arrows indicate the direction in which the syllable frequency was expected to change in response to DAF. Larger error bars on day 12 are mostly due to the smallest number of target syllable renditions (n = 126) sung on that day.