 These pathways are just exaggerated in those with synesthesia

It has been shown that neurologically normal persons as young as 2.5 years of age demonstrate a type of synesthetic cross-modal associations.In 1929, Wolfgang Köhler ran an experiment in which a group of native Spanish speakers would assign the name “takete” or “baluba” to a set of round or jagged shapes.It was concluded that people had a strong preference to calling the jagged shapes “takete” rather than “baluba”.