The mystery of the rounder, sweeter chocolate bar.

People are known to associate sweetness with roundness and angularity with bitterness and, hence, making a traditionally rectangular food rounder may be expected to alter the perceived taste by priming notions of sweetness in the mind of the consumer. (2013)
Read more: https://flavourjournal.biomedcentral.com/articles/10.1186/2044-7248-2-28?source=Snapzu