| Summary: | Chewing gum has previously been found to reduce chronic stress and enhance alertness, but effects on attention have been less reliable. The aim of this thesis was to investigate possible mechanisms for such effects, and to study the reliability and timing of effects in greater detail. Two surveys provided detailed information about habitual gum consumption. Two intervention studies involved chewing gum during a workday and reporting well-being and performance at work; the second intervention also assessed physiological variables. Six experiments studied the timing of and mechanisms for acute chewing gum effects. Two of these experiments studied the prevalence of time-on-task trends in gum effects on attention and mood. A further experiment studied the effects of gum on mood in the absence of attention tasks. The final three experiments examined possible mechanisms for consistent effects of gum on alertness and variable effects on attention: the first concerned psychophysiology, the second concerned demand characteristics, and the third concerned rate of chewing and task order. The results of this thesis suggest that chewing gum can reliably maintain alertness and enhance reported performance at work. Chewing gum also moderated decrements in vigilance, although the direction of this effect depended on length of prior performance. A reduction of stress and anxiety was observed in some cases, but this finding was less reliable. Under experimental conditions, heart rate increased while chewing gum and began to slow following chewing, suggesting a physiological mechanism for both enhanced alertness and reduced stress. However, heart rate did not differ over the course of a workday. Salivary cortisol was higher during the morning when chewing gum, suggesting an endocrine response associated with higher alertness. Demand characteristics moderated reported alertness, but did not explain any effects on attention. Neither rate of chewing nor task order moderated chewing gum effects.
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