Academic journal article Canadian Journal of Experimental Psychology

The Role of Sensory Factors in Cognitive Aging Research

Academic journal article Canadian Journal of Experimental Psychology

The Role of Sensory Factors in Cognitive Aging Research

Article excerpt

Abstract Performance on complex, cognitive tasks often is sensitive to low-level sensory and perceptual factors. These relations are particularly important for cognitive aging researchers because aging is associated with a variety of changes in sensory and perceptual function. In the article that follows, I first selectively outline some relations between task performance and sensory function. Next, I summarize age-related changes in visual function and the implications of these changes for task performance, using the digit-symbol subtest of the WAIS as an example. I offer some reasons why age-related sensory decline may not be important to all cognitive tasks. Finally, I provide several recommendations for cognitive gerontologists who want to minimize the risk that the age differences they observe are sensory in nature.

The past decade of cognitive aging research has produced a small, but provocative and influential number of studies that suggest a rather strong correlation between age-related differences in sensory measures like visual acuity and cognitive measures of attention, memory, and intelligence. Understandably, these data are generating an uncertain and mixed reaction within the gerontological community. On the one hand, the possibility of a common or general cause of cognitive aging has parsimonious and clear intellectual appeal. On the other hand, such findings complicate the work of researchers who wish to attribute age differences in task performance to cognitive mechanisms.

To motivate the discussion by example, Lindenberger and Baltes (1994) assessed corrected visual acuity and audiometric thresholds, along with several measures of cognitive function (e.g., reasoning) in over 150 people older than 70 years of age. The interrelationships among some of the variables are shown in Figure 1. Aging is strongly correlated with both visual and auditory function, which in turn have a substantial impact on cognition. Such a pattern is consistent with the view that age changes in cognition reflect a common factor that is also indexed by sensory function. However, the data are also compatible with the assertion that age differences in cognition are caused by sensory deficits that make it more difficult for the elderly to process the test materials. In fact, this is the position implicit in the model shown in Figure 1, because age impacts cognition only indirectly through its influence on sensory function.

The substantial relations between sensory and cognitive function are not, as might be hypothesized, a result of selecting only an older sample in which undetected disease causes correlated interindividual differences in sensory thresholds and cognitive behaviour. Moderate to large correlations between age, sensation, and cognition have been found in life-span samples (Baltes & Lindenberger, 1997; Salthouse, Hancock, Meinz, & Hambrick, 1996) and in longitudinal designs (Schaie, Maitland, & Willis, 2000). Neither do the correlations result spuriously from age-related changes in response criterion (Burton, Owsley, & Sloane, 1993; Higgins, Jaffe, Caruso, & de Monasterio, 1988). Stevens, Cruz, Marks, and Lakatos (1998) found correlations between forced-choice measures of sensory function and performance on the Boston Picture Naming Test and Logical Memory subtest of the Wechsler Memory Scale ranged from .35 to .78 in small, select groups of younger and older adults. The magnitude of the relationship appears to vary with sensory modality, but not always in ways that allow for easy causal models. For example, Glass (2000) reported that visual contrast sensitivity accounted for more age-related variance in spatial tasks than in verbal tasks. On the other hand, Stevens et al. found that it was touch and taste thresholds that had the highest correlations with the Logical Memory test. The sensory-cognitive link appears to be quite robust, crossing task domains as diverse as problem-solving and fluency (Lindenberger & Baltes, 1994), concept identification (Salthouse et al. …

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