Have you ever noticed that death metal bands use spiky font but that romantic poetry is written in flowery curlicues?  Is that a cultural accident? Or is there a deep connection between shape and sound?  We found evidence for the deep hypothesis in two different cultures -- the US and a remote village in Cambodia. Both cultures matched shapes and sounds by spectral energy. Both cultures also used spectral energy as a proxy for emotional arousal. This makes sense because we make higher energy sounds and movements when we are angry or excited.  And it suggests that the human brain efficiently extracts spectral energy in what we see and hear in order to make rapid inferences about emotion.  

Video abstract of this paper -- created by Beau Sievers.  To read about the spectral energy hypothesis, click here.  And here we demonstrate the neural efficiencies in visual and auditory cortex that make these connections possible.