(Photo: Jeroen van de Sande/STOCK.XCHNG)

Listening to Heavy Metal Music, such as Iron Maiden and Metallica, in utero has developmental implications, according to a recent longitudinal study published in the Journal of Infant Development.

Foetuses exposed to Heavy Metal music for 25 minutes a day in the second and third trimesters of pregnancy have been found to be have 18% higher levels of pre-natal testosterone, levels that do not appear to decrease until after the 5th year of development.

Dr. Hetfield, lead author of the study, claims increased testosterone can have developmental implications. "Primarily we found increased levels of trait aggression", Hetfield said. "What we didn't expect was that at these levels of Heavy Metal exposure, male infants, in particular, were born with a significant degree more hair on their scalp".

In a series of 12 follow-up studies, conducted every 6 months after birth, researchers found that infants grew slightly faster and larger than controls, continued to grow unusual lengths of head-hair, and displayed higher levels of trait aggression than controls, or levels of parental testosterone would have predicted.

"We're calling this the Metallica Effect", Dr. Hetfield said, "it is completely counter-intuitive that loud rock music should have this kind of influence over the development of the embryo". Dr. Hetfield speculates that the volume of the music, as well as the dominant percussive rhythms and unique vocal 'screaming' triggers evolutionary responses for the foetus to grow larger, stronger and more 'primal' than control. "I guess we're mimicking conditions similar to early hominid warfare. You can see the advantage in growing faster and stronger when such cues are present".

###

Developmental Science: http://www.HappyApril1st.com