Conjugating the "tenses" of function: discordance among hypothetical, experimental, and enacted function in older adults.

Within the field of aging, the conceptualization and measurement of functioning has been dominated by the disability model. In this paper, one limitation of that model is described by calling attention to a distinction between three "tenses" of functioning. Inadequate attention has been paid to the distinction between the capacity to function in the abstract (hypothetical tense) and actual performance in daily life (enacted tense). Failure to attend to this distinction has obscured considerable discordance between what people say they are able to do in standard functional disability assessments, and what they actually do at home. To illustrate this point, data from the MacArthur Studies of Successful Aging comparing the hypothetical to the enacted tenses are presented. These data show a consistent pattern of discordance between these two tenses.