Assessment of chemosensory functioning in aging. Subjective and objective procedures

Assessments of human sensory and perceptual functioning are meaningfully classified as either subjective or objective. Both subjective and objective measures have been employed in studies of age-related changes in chemosensory functioning. Subjective and objective assessments proceed from different philosophic assumptions, provide different types of information, and play different roles in understanding age-related change. Subjective assessment exploits each person's unique access to the functioning of his or her own sensory apparatus. It assumes that subjects can and will give an accurate account of their sensory experience and is distinguished by the attempt to directly communicate private experience. Objective assessment strategies circumvent the practical and philosophical problems of verifying and communicating private experience. Objective measures assume that sensory function is reflected in the subject's performance of tasks that require perception of the relevant sensory information. Subjective measures are primarily descriptive. They can be used to characterize chemosensory experience and may reveal the fullness and drama of age differences. Objective measures, while they may fail to capture the richness of perceptual experience, are directly relevant to the investigation of the underlying mechanisms. Thus, subjective measures serve to direct attention to the issues and phenomena of perceptual change in aging whereas objective measures are most useful for specifying and evaluating candidate mechanisms by which these changes might be generated.