 Marler and Tamura noted that this case of cultural transmission was interesting because it required no social bond between the learner and the emitter of sound (since all sounds originated from a loudspeaker in their experiments).However, the presence of social bonds strongly facilitates song imitation in certain songbirds.Zebra finches rarely imitate songs played from a loudspeaker, but they regularly imitate songs of an adult bird after only a few hours of interaction.