Whenever it hears an unfamiliar song from a male of the same species, a zebra finch stops chirping, hopping and grooming. Once it becomes familiar with the song, it goes back to its busy routine. Researchers have now found that levels of microRNAs -- short lengths of ribonucleic acid -- go up or down in the songbird brain after it hears a new song. These microRNAs likely represent a new class of regulatory agents that fine-tune the brain's response to social information.

Source: MicroRNAs in the songbird brain respond to new songs