Fig. 1.

A Go-NoGo auditory discrimination task. a When the experimenter (EXP) was on the perch continuously for 3.5 s, an acoustic stimulus S_i (i = 1,..,10) was randomly chosen and played through a loudspeaker. In this example, the long stimuli (S₆ to S₁₀) were followed by an air-puff aimed at the experimenter. Experimenters were expected to learn to avoid the air-puffs by escaping the perch in puffed trials, and staying on the perch in unpuffed trials. b Log-power spectrograms of all ten stimuli in the training set (S₁ to S₁₀, left) and in the generalization set (S’₁ to S’₁₀, right). All stimuli were composed of a string of six renditions of a particular song syllable. c Syllable durations for the ten stimuli in the training set (blue) and generalization set (red, dots indicate individual syllable renditions). Either the long stimuli or short stimuli were followed by an air-puff