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PAL. (a) The pre-training phase in which both birds are presented with a white bead three times, (b) the training phase in which one bird (the demonstrator) is presented with a red (darker) bead (either dry or covered with the bitter-tasting substance MeA) and (c) the testing phase in which both chicks are presented with (i) a dry red (darker) bead followed by (ii) a dry white bead.
