A few years ago, I ran an online experiment for the Manchester Science Festival that got people listening to screams and rating them for scariness. Last week I removed the experiment from the servers because browsers have stopped support Flash. This gave me an excuse to re-examine the results.
There were 19 screams used, and over the last 4.5 years, there have been 111,379 ratings of scream, that equates to roughly 20,000 people taking the experiment. Thanks to everyone who took part.
Women have scarier screams than men
The three worst screams were from females. On average, women had scarier screams (Mann-Whitney test, U(N=11379) = 3.1E9 , Z = -31.6, p<0.001), effect size = 0.09, small).
An ‘average’ male scream
Women’s screams are usually a higher pitch than men’s and so are closer to the frequencies where peoples’ ears are most sensitive – about 3000Hz. It is possible to speculate about sociological factors as well. Traditionally, men protected women and children, so maybe that is why the reaction to high-pitched screams is stronger.
Rougher screams are scarier
Scream with roughness:
Scream with less roughness
It’s all about the screamer sounding really distressed. Ask the average person on the street to scream and they tend to be a bit inhibited and the sound isn’t very scary. When they really go for it, push lots of air very fast out of their lungs, you get a high-pitched, rough sound as the vocal chords struggle to cope, and it’s really unpleasant to listen to; a similar effect is heard at the climax of chimpanzee hoots.
This result was also found in a more recent and extensive study into screaming. That study showed that the rough sound produced modulation in the frequency range 30 – 150 Hz. And this roughness selectively activates the amygdala, a part of the brain involved in processing danger signals.
19 screams were used in the experiment, with each visitor played six. There was no difference in the voting patterns of men and women and very little over different age groups. Given that screaming is a distress call, may be it isn’t so surprising that we all respond the same to it.