screaming for science: the secrets of crying babies and car alarms - the best car alarm
It is almost impossible to ignore a screaming baby. (
If you doubt this, please click here. )
Now scientists think they know why.
"Screaming takes up a small piece of their own that doesn't sound like it's being used for other things," says David Poeppel, professor of psychology and neuroscience at New York University and head of the Department of Neuroscience at the marpu Institute in Frankfurt.
When people hear the unique sound features of screaming
From a baby or someone else.
It triggers the fear loop in the brain, and Poeppel and a research team report in Cell Biology.
The team also found that certain artificial sounds, such as alarms, trigger the same circuit.
"That's why you want to throw the alarm clock on the floor," Poeppel said . ".
Researchers at the Poeppel lab decided to study screaming, in part because they were an original form of communication found in each culture.
There's another reason.
"Many of my lab's postdoctoral fellows are in the process of having children, and of course, they are very concerned about screaming," said Poeppel . ".
"So it makes absolutely sense that they are obsessed with this topic.
"The team first tried to figure out what made the scream," said Poeppel . ".
To answer this question, you need to create a large database with screaming records.
From movies, the Internet and volunteers, they agreed to walk into a sound booth.
Carefully analyze these screams and find that they are not like any other sound made by people, including other loud, high voices
This difference is referred to as the amplitude modulation rate, which is the frequency of the change in sound loudness.
When someone talks, the modulation rate changes about four or five times per second.
But when someone screams, it can jump more than 100 times per second.
This gives sound a sound quality called roughness.
So we hear the audio of the "rough sound" clip you see below, not the high, large, "smooth sound" clip below that clip.
"Screaming is the only thing humans have this rough sound," Poeppel said.
But "car alarms, house alarms, alarms work exactly the same, they have this roughness modulation," he said . ".
To understand how these sounds produce such a direct and strong response, the team uses functional MRI to monitor the brain when people listen to a variety of sounds, including screams.
The experiments show that screaming has a unique ability to cause the activity of the almond body, "the circuit associated with producing a fear response," Poeppel said ".
The screaming rated particularly horrible by the audience generated the highest level of activation.
So why did humans evolve to scream?
Some of the answers may involve babies, Poeppel said.
He suspects that babies may be more likely to survive if they can immediately activate the almond body of their parents or caregivers.