As expected, the musicians had an enhanced ability to pick up on the emotional cues of the sound. But the researchers were a little surprised to learn that the musicians were more attuned to the complex sounds -- those carrying the most emotion -- than to the less significant "periodic" sounds of crying. That allowed them to devote more resources to the important sounds and virtually ignore the sounds that carried little emotion.
That reflects an increased economy of resources -- don't waste energy listening to something that says nothing.
"Enhancements, reflected by larger time -- and frequency -- domain response magnitudes, were most evident in musicians' responses to the most complex portions of the sound, with economy (smaller amplitudes) seen in their responses to the periodic portion," the researchers report.
The findings might seem open to the chicken-and-egg debate. Did the musicians perform better because they are naturally more sensitive to sounds, and thus more likely to study music? Or did their nervous systems change because they were exposed to music for more than a decade?
The researchers feel confident the correct answer is the latter.
"With musician studies you always wonder if the person was just born with a more accurate sensor," Kraus said. "And there's probably an element of that. We're all a combination of nature and nurture."
But the fact that all the musicians performed so much better than the nonmusicians clearly shows that the study of music -- not an innate musical aptitude -- literally changed the way the musicians' brains processed sounds, the researchers concluded.
"Our results provide evidence for a subcortical role in the processing of emotional cues by showing that auditory brainstem responses to emotionally salient vocal sounds are dynamic, shaped by life-long, multisensory experience with auditory signals," the researchers note. "These responses are not hardwired but malleable with extensive auditory training."
In other words, we aren't just who we are. We're also what we have done.