Scientists check for the behavioral hallmark of a significantly higher retest consistency after at least a year compared to control groups.
[7] Examples of many well-known synesthetic taste experiences are recorded in case studies with singular participants that demonstrate the variability of the condition.
[1] In many forms, more well-known words and words used with a higher frequency are more likely to have a strong taste association [2][7] The phonological roots associated with this form of synesthesia drive the current research on lexical–gustatory synesthesia to determine which parts of the brain are active in synesthetes causing the neurological cross-talk condition and how the findings may relate to neurologically normal persons.
Tip of tongue studies have shown that a word’s lemma may be responsible for eliciting a taste sensation, not its phonologic sound or spelling.
[2][4] SC is a synesthete who automatically experiences smells, tastes, and feelings of textures in her mouth and throat when she reads, speaks, or hears language, music, and certain environmental sounds.
In SC’s case study, researchers utilized fMRI to determine the areas of the brain that were activated during her synesthetic experiences.
The scans led researchers to speculate that the anterior insula may play a role in SC’s taste experiences while the superior parietal lobe binds together all of the sensory information for processing.
[8] During PS’s study, researchers determined the consistency of her responses to be greater than 99% over a three-week period, indicating the validity of her condition.
A result of her study demonstrated that merely listening to someone speak a string of words in quick succession, such as reading, did not evoke synesthetic tastes.
This led to the implication that single words must be focused on in order to activate the inducer-concurrent taste in certain forms of lexical–gustatory synesthesia.
It is possible that incomplete synaptic pruning during childhood development could lead to the continued maintenance of connections that are normally severed in the process.
The maintenance of these connections would then lead to the cross-linking of areas in the brain that do not normally interact with one another and the possible mixing of senses.
[2][5] Another possible neurological mechanism that may contribute to synesthesia is an increased structural connectivity in the brains of synesthetes as shown using diffusion tensor imaging (DTI).
[1][2] 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, psychologist 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 found that the participants could pick out certain abstract clues from the different foods tasted and associate them in a significant manner to meaningless non-words.