Joseph C. Stevens John S. Pierce Foundation Laboratory, and Yale University
About a decade ago interest arose in our laboratory in how aging may change the functional properties of the chemical senses. Earlier, measurement of thresholds tended to dominate this subject, typically showing an elevation from the third to the eighth decade of about tenfold for olfaction and from about two- to nine-fold for gustation. Although the last 20 years have seen the proliferation of methods for studying suprathreshold functioning (e.g., tests of odor and food discrimination; Schiffman & Leffingwell , 1981; Schiffman & Paskernak, 1979), odor and food identification ( Doty et al., 1984; Murphy, 1985; Schemper, Voss, & Cain, 1981; Schiffman , 1977), odor memory ( Cain & Murphy, 1987), and olfactory adaptation ( Stevens, Cain, Schiet, & Oatley, 1989), our earliest interest centered on suprathreshold magnitude and especially whether thresholds predict a corresponding weakening of the tastes and smells associated with more crucial levels encountered in eating and drinking.
This question bears on the senses in general. It is perhaps best illustrated by the study of hearing, where we know that threshold loss may predict loudness (as in conduction deafness) or fail to do so (as in "nerve" deafness). The latter may disturb threshold but spare suprathreshold loudness at, say, typical speech levels.
To study suprathreshold tastes and smells, cross-modality matching springs first to mind as a useful method. By this method chemical stimuli (along a "target" continuum say taste or olfaction) would be matched by stimuli along a "standard" continuum, say loudness or brightness.