By Steven Brown and Xiaoqing Gao
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Our interpretation of the result comes from cognitive theories of emotion that argue that aesthetic processing is, at its core, the appraisal of the value of an object -- in other words, an assessment of whether an object is “good for me” or “bad for me.” The nature of this appraisal depends very strongly on what my current physiological state is. The sight of chocolate cake will lead to positive aesthetic emotions if I’m famished but to feelings of disgust if I’m sick to my stomach. Objects that satisfy current physiological needs will lead to positive aesthetic emotions (e.g., pleasure). Those that oppose these needs will lead to negative emotions (e.g., repulsion).
How does the anterior insula fit into this story? In thinking about the contrast between internal and external environments, the anterior insula seems to be much more associated with the former than the latter. It is part of the brain’s “interoceptive” system, evaluating the state of the organs of our body. Other parts of the brain, then, respond directly to objects in the external environment: the sensory pathways of the brain. (One part of the cortex that seems particularly important for processing information across many sensory modalities is the orbitofrontal cortex.)
Brain areas such as the anterior insula and orbitofrontal cortex that are activated by pleasant smells or tastes are also the parts of the brain that are active when we are awed by Renaissance paintings or Baroque concertos. There is virtually no evidence that artworks activate emotion areas distinct from those involved in appraising everyday objects important for survival. Hence, the most reasonable evolutionary hypothesis is that the aesthetic system of the brain evolved first for the appraisal of objects of biological importance, including food sources and suitable mates, and was later co-opted for artworks such as paintings and music. As much as philosophers like to believe that our brains contain a specialized system for the appreciation of artworks, research suggests that our brain’s responses to a piece of cake and a piece of music are in fact quite similar.