MONDAY, 3 AUGUST 2015They asked volunteers to rank a variety of sounds by how alarming they were (natural and synthetic sounds), if they think the speaker felt fear (neutral vowels (“Aaaaah”) or human screams and neutral or screamed sentences such as “Oh my god help me!”). For control experiments, they also measured the effect of normal vocalisations made rougher, and screams with subtracted roughness. Only sounds with the roughness factor elicited negative feelings of alarm, regardless of whether they were human or synthetic, suggesting that alarms were unknowingly designed to mimicking the roughness component of human screams.
A functional magnetic resonance imaging (fMRI) experiment also showed that these rough sounds activate the amygdala, fear centre of the brain, while neutral sounds do not. Thus, roughness in screams might be a unique quality of sound that directly elicits a careful, negative response unlike any other language signals.
Written by Laura-Nadine Schuhmacher.