Nancy R. Sizer’s research while affiliated with Harvard Medical School and other places

Motivational levels are elevated when individuals believe that they have control over tasks and over behavioral outcomes. When individuals are permitted to make choices, their perception of control increases. In addition, by enhancing motivation, the exercise of choice facilitates performance on a variety of cognitive tasks. However, with advancing age or in the presence of a chronic disease such as diabetes, the effectiveness of choice in improving performance is attenuated. Despite these limitations on the effectiveness of choice, cognitive performance can still be improved significantly by the simple expedient of increasing the perception of control. Increased motivation appears to improve performance by suppressing interference from background stimuli. That is, decreased concentration on relevant target stimuli and increased interference from less relevant background stimuli are characteristics of the decline in cognitive function in the aged. This reflects a decrease in differentiation, a putative cognitive process that identifies target and background stimuli and appropriately proportions cognitive resources to them. When differentiation is effective, interference from background stimuli decreases. Because differentiation is an effort demanding process, its effectiveness depends upon an adequate level of motivation. Research indicates that the degree to which an individual differentiates predicts performance on a variety of cognitive tasks. Overall, these findings are hopeful in demonstrating that choice can serve as an effective motivational intervention for decreasing the rate of cognitive decline and improving the quality of life in vulnerable older individuals.

Non-insulin-dependent diabetes mellitus is present in 7-10% of the aged. This disease appears to be associated with an acceleration of the aging process and results in compromised performance on learning and memory tasks. The present study used a verbal fluency test to examine semantic memory performance in two age groups (55-64 and 65-74 years) of diabetic subjects and controls. In addition, immediate and secondary memory were also examined using the digit symbol and digit span tests and a serial learning task. Results showed that digit symbol performance was poorer for older subjects and diabetics while serial learning was poorer only for diabetic subjects. However, the number of words generated on the verbal fluency test was similar for all groups. Qualitative analyses of the verbal output revealed that older subjects and diabetics produced the greatest number of previously recited words (repetitions). Repetitions may signal a failure to adequately monitor behavior which in turn could contribute to cognitive decline.