On the singularity of taste sensations: What is a taste primary?

It is commonly accepted that there are four primary tastes. This conceptualization is notable for its simplicity and usefulness in guiding research and organizing data in the stimulus, receptor, neural and psychophysical aspects of taste. But however strongly defended or widely used, the concept of a primary taste remains undefined, especially in the psychophysical sense. The present research sets forth and tests one psychophysical defining property of a taste primary, that it should appear singular, and remain singular when mixed with other tastes; i.e., several singular tastes, when mixed, should remain separate and distinct. It is shown that mixtures are often judged to be as singular as their separate components, indicating synthesis of new tastes different from the components, and thus the existence of more than the few primary tastes.