Task Switching Over the Lifespan

People often switch from one goal to another, in response to changing environmental demands. Task switching affords flexibility, but at a price. A robust switch cost ensues, whereby individuals are slower and less accurate when switching between tasks than when repeating tasks. The current dissertation investigated the factors that contribute to a switch cost, using an exceptionally large sample of over 25,000 individuals (ages 10 to over 65) collected online.

Switch costs are interpreted as the duration of psychological processes that are recruited to shift between tasks. In Study 1, shifting a task took 576 ms (or 108%) longer than performing a single task. Shifting tasks resulted in a 34% immediate decrease in productivity. An additional 74% long-term decrease in productivity occurred from maintaining readiness for a shift, and for using a cue to select a task, both of which occur even without an actual shift taking place. The results show that the seemingly simple switch cost involves multiple processes.

Understanding these processes is crucial to interpret how flexibility varies with age. In Study 2A, task switching process developed until adulthood and then declined, similar to general cognitive ability. However, each process changed differently with age. Findings show that decline is not simply development in reverse: The rate of decline in mid to late adulthood was up to 20 times slower than the rapid development in adolescence; Middle-aged adults were slower than young adults, but as accurate; They maintained less advance readiness but used contextual cues as well as their younger counterparts. In Study 2B, the effects of age were replicated in an independent sample using identical methodology. These findings highlight the usefulness of web-based data collection, effect size estimation, and segmented regression techniques.