Age and task difficulty differences in dual tasking using circle tracing and serial subtraction tasks

The aim of this study was to investigate age-related differences in dual task performance by using an upper limb prioprioceptive task. Twenty-eight younger (18-30 years) and 28 older (> 60 years) healthy adults performed circle tracing and serial subtraction tasks separately and concurrently. Tasks had two levels of difficulty: easy and hard. The circle tracing task included direct (easy) and indirect (hard) visual feedback conditions, and it was paired with serial subtraction by twos (easy) or by threes (hard). We found that older adults were significantly slower than younger adults across all conditions, and had significantly greater dual task costs when they performed circle tracing with easy serial subtraction. Higher levels of task difficulty were associated with slower speed in both groups. We found no age differences in accuracy. Participants either traded speed for accuracy or accuracy for speed regardless of age group. Overall, the findings suggest that speed and accuracy may be affected differently during dual tasking. In addition, older adults may rely more extensively on proprioceptive feedback to guide upper limb movement compared with younger adults.