Age and Function Differences in Shared Task Performance

Everyday activity often involves performing two or more simultaneous actions. Common examples are carrying groceries while walking, monitoring traffic while crossing the street, and walking while talking to another person. In older adults, simultaneous performance of two tasks has been shown to lead to performance declines in one or both tasks (Lundin-Olsson, Nyberg, & Gustafson, 1997; Woollacott & Shumway-Cook, 2002). Much of the previous research focused on shared and dual task performance in individuals with cognitive challenges or at risk for falls. Lundin-Olsson and colleagues (1997) found that older adults with a history of falls were unable to carry on a conversation while walking. These individuals tended to stop walking in order to talk with a companion. More recently, Sparrow, Bradshaw, Lamoureux, and Tirosh (2002) determined that increased attentional demands during gait, such as talking, increased reaction time. Increased reaction time during gait may predispose older adults to falls due to a decreased ability to avoid environmental changes, such as circumventing obstacles in their paths. ShumwayCook and colleagues (1997) found that individuals with a history of two or more recent falls swayed more during quiet stance than nonfallers as they completed a series of simultaneous cognitive tasks. Investigating the demands of simultaneous static balance and cognitive tasks has demonstrated the attention-demanding nature of even quiet stance. There have been fewer investigations of shared performance of dynamic tasks; it is equally important to determine the impact of the changing demands of these tasks on older adults. As noted previously, Lundin-Olsson and colleagues (1997) determined that older adults with a history of falls were unable to perform two tasks simultaneously. Many participants in their investigation were cognitively impaired, were depressed, or had had a stroke. Bowen and colleagues (2001) also reported gait changes among older adults recovering from stroke. Velocity decreased and double-support time increased, when these individuals attempted a simultaneous cognitive task. Other investigators have examined dual-task performance in healthy older adults. Chen and colleagues (1996) found that errors increased in both younger and older participants who responded to a visual reaction-time stimulus while walking and attempting to avoid a virtual object. The magnitude of increase was greater for the older adults. Other researchers suggested that a dual task situation requiring memorization also significantly impacts performing a secondary task, including walking over level surfaces. Additionally, there is evidence that cognitive tasks increase alterations in motor performance with increased age (Li, Lindenberger, Freund, & Baltes, 2001; Lindenberger, Marsiske, & Baltes, 2000). Less is known about the effects of normal aging on speech output than other motor actions, because studies of communication integrity have focused on voice production and linguistic parameters rather than speech production characteristics. Studies investigating Age and Function Differences in Shared Task Performance: Walking and Talking