The current series of experiments investigated the effects of the timing of gum chewing on cognitive function, by administering a battery of cognitive tasks to participants who chewed gum either prior to or throughout testing, and comparing their performance to that of controls who did not chew gum. Chewing gum was associated with performance advantages on multiple measures when gum was chewed for 5 min before, but not during, cognitive testing. The benefits, however, persisted only for the first 15–20 min of the testing session, and did not extend to all cognitive domains. To explain this pattern of results, it is proposed that the time-limited nature of performance benefits can be attributed to mastication-induced arousal. Furthermore, the lack of improvement in cognitive function when gum is chewed throughout testing may be because of interference effects due to a sharing of resources by cognitive and masticatory processes. This dual-process mechanism is not only consistent with the outcome of present experiments but can potentially account for a wide range of findings reported in the literature.