Salimpoor monitored how the volunteers' brains reacted to the music using MRI. Multiple brain regions activated when they discovered a new favorite song, but only activity in the nucleus accumbens was well-correlated to how much the participants were willing to pay, she and colleagues reported online Thursday in Science.
The nucleus accumbens is believed to be responsible for pleasant surprises, or "positive prediction error," as neuroscientists call it. Our brains are well-suited to using patterns, such as the structure of music, to predict the future. "We're constantly making predictions, even if we don't know the music," Salimpoor says. "We're still predicting how it should unfold."
These predictions are based on past musical experience, so classical fans will have different expectations than punk devotees. But when the music turns out better than the brain expected, the nucleus accumbens fires off with delight. Salimpoor concluded that the nucleus accumbens works in concert with pattern recognition and higher-order thinking centers to assign value to music.
Vinod Menon, a cognitive neuroscientist at Stanford University in Palo Alto, Calif., wonders if the presence of lyrics in some tracks introduced confounding variables. "We don't know if it's the musical sounds or the linguistic components that drove some of these effects," he says. Salimpoor responds that previous research showed similar brain effects using only instrumental music. Lyrics, she says, did not appear to skew listener's purchasing decisions.
Next, Salimpoor will investigate another area of the brain, the superior temporal gyrus. She aims to discover how this region, which stores a record of the sounds we've heard, shapes our future musical preferences. Eat your heart out, Pandora.