They found that the birds’ reacted far more strongly to the duet than when they sang their parts alone. The research is in the journal Science. That’s fine for Ecuadorian birds but what about us humans? Well, vertebrate animals all have similar neurotransmitter systems and the brain is organized in much of the same way -- so the paper’s authors hold that there is relevance to the human brain. Or at least to those vertebrates who have a tendency to cooperate in the first place.