| Abstract: | The present investigation explores the stimulus–response(psychophysical) functions for total nasal perceived intensityfor two pungent odorants, formaldehyde and ammonia, presentedeither alone or with different backgrounds of the other irritant.Stimuli were comprised of four formaldehyde concentrations (1.0,3.5, 6.9 and 16.7 p.p.m.); four ammonia concentrations (210,776, 1172 and 1716 p.p.m.); and their 16 binary mixtures. Ammoniafunctions showed a consistent upward concavity. At low, mediumand high concentrations, the total perceived intensity of themixtures showed hypoadditivity, simple additivity and hyperadditivity,respectively. That is, the intensity of the corresponding mixtureswas significantly lower than, equal to, or greater than thesum of its components. The progressive involvement of pungency,aroused by common chemical sense stimulation, may be responsiblefor the increasing additivity observed. Simple additivity, andeven hyperadditivity, may characterize mixtures involving commonchemical stimulation. |
