Figure 2.

Classical oddball paradigm and alternating oddball paradigm. In the classical oddball paradigm, two stimuli were presented in two blocks with different probabilities. For notation purposes, when a stimulus is presented with low probability, it is called the deviant and the stimulus immediately preceding it is called the standard. Deviant and standard are color-coded with red and blue, respectively. The alternating oddball paradigm includes the alternating and control condition. In the alternating condition, two stimuli (A,B, one canary and one zebra finch syllable) were initially presented in alternation 25 times to familiarize the bird with the stimuli and the alternation pattern. Then, rare repetitions were presented after a variable 4–10 regular alternations. The deviant (2nd stimulus in the repetition), standard (1st stimulus in the repetition), and the stimulus immediately before them formed a “triplet.” In the control condition, the number of stimulus trials and the positions of the triplets were the same as those in the alternating condition, however, stimulus sequences between the triplets were shuffled in the control condition.