Experimental psychologist Charles Spence and colleagues at Oxford University have found that people generally tend to associate larger shapes with lower pitched sounds and smaller shapes with higher sounds.
It seems our brains may use these synaesthetic associations, says Professor Spence, "to combine all of the different sensory cues that are hitting our receptors at any one time".
Which one of these shapes is 'bouba' and which one is 'kiki'?
Most people label the amoeboid-like shape a bouba, and the star shape a kiki. Further, Spence says that people tend to associate certain sounds with foods.
He said that two of the best examples are brie, which is "very maluma", whereas cranberries are "very takete".
Spence is working with a world-renowned chef to combine name dishes in way that influences their taste buds. But, is there anything to this but amusement?
Synaesthesia can be the stuff of what might be called pathologic brilliance. The well-known autistic mathematical genius Daniel Tammet (his blog is here) says that he sees numbers as shapes and colors. He wrote the books Born on a Blue Day and recently Embracing the Wide Sky. There are other examples. Whatever autism is (and it's probably a single term for a host of different places on the range of neural variation), a kind of remoteness from the everyday world of most people may be associated with aspects of mapping associations in the brain.
But if these are all very interesting facts, but what do they tell us about how our brains work? There is a lot written these days about fMRIs, or functional magnetic resonance imaging, that purports to show which part of the brain is 'for' what function. But, in fact most published fMRI images are composites from multiple people, because the brain isn't as divisible and predictable as it might seem. And, studies of the brains of people who lose a sense, such as vision, show that the part of the brain that was once 'for' vision can be remapped to touch or hearing.
From an evolutionary genetic point of view, this work seems to point to the idea that mammal brains evolved to localize types of function in ways that sequester them from each other--perhaps to enable easier recall, the way books in a library are catalogued by category numbers for easier shelving.
But memories and thoughts cannot be wholly sequestered, or animals could not integrate information to make holistic sense of their environment--which is vital to find food, detect predators, recognize mates and kin, and so on. The partial nature of sequestration is a fundamental aspect of life--all life--and is one of the generalizations about life that we explore in our book (and this blog).
Clearly, cultural experience associates different kinds of information. In our culture, we associate low sounds with large size, because many things that are large, like empty barrels, tubas, and so on make large sounds, while small birds & piccolos make high ones. But the fact that we make such associations, and ones like the shape-test above, does not imply that we're hard-wired to make them.
Too much genetic hardwiring would potentially cripple an organism to conditions its ancestors dealt with and that selected the lucky hard-wired ones for reproductive success. But it could be a disaster if environments change. Clearly, we think, it is functionally better to be soft-wired: genetically enabled to make associations by experience, file them, and recall them systematically as needed--this kind of adaptability is another generality about life that we explore in our book. Whether it's harder to understand how genes could evolve to be soft-wired rather than hard-wired is debatable, but most research in evolutionary biology is about what's hard-wired and takes a hard-wiring perspective.
Synaesthesia shows that the wires can become crossed in some people (at least sometimes for reasons having to do with genetic variation). But, in general, mammals are master electricians who install the wiring in each case where it best needs to be.