Blood-curdling screams pierce the brain. Unlike other vocalizations, screams contain an acoustical signature that alerts the brain to danger, scientists report July 16 in Current Biology. The results help explain why screams are such an effective method of communication.
By analyzing the acoustical makeup of sounds, David Poeppel of New York University and the Max Planck Institute for Empirical Aesthetics in Germany and colleagues found that screams scored high on measures of “roughness.” That quality features big swings in loudness and an unpleasant perception. Normal speech isn’t very rough, but car and house alarms are, the researchers found. Smoothing out the rough signals in screams led people to say the screams weren’t as scary.
Rough screams came with more activity in the amygdala, a structure in the brain that helps a person detect threats, functional MRI brain scans revealed. The results help explain why screams are so distinctly alarming.