The Four Questions: The requirement to test four parameters of taste and smell function to diagnose and treat taste and smell disorders

To diagnose and treat taste and smell disorders it is necessary to determine quantitatively several aspects of taste and smell function. To do this it is necessary to test four parameters of each of these sensory functions. These tests require answers to four questions: (1) Can you detect a tastant or odorant as different from two blank substances? (2) Can you recognize the tastant or odorant as characteristic of a specific sensory quality, e.g., NaCl as salty, amyl acetate as banana oil? (3) Can you judge the sensory strength on a standardized quantitative scale over a range of sensory stimuli? and (4) Can you judge stimulus pleasantness or unpleasantness appropriately on a standardized quantitative scale over a range of sensory stimuli? Answers to these four questions allows determination of four basic parameters of sensory function: (1) detection threshold – determines if sensory receptors are functioning; (2) recognition threshold – determines the connectivity between functioning sensory receptors and the brain; (3) magnitude estimation – determines the number of functioning sensory receptors; and (4) hedonics – determines the presence or absence of distortions in processing of sensory information relating receptor and brain. Only by use of these four tests can taste and smell function be evaluated quantitatively and effectively to diagnose and treat taste and smell disorders.