Sunday, August 10, 2014

The perks of a pack of gum

Besides drinking caffeine-rich beverages, I've heard anecdotally that some long-distance drivers will chew gum behind the wheel to avoid paying an untimely visit to the land of snooze. A recent research article has looked at the potential alerting effect of gum in the lab, looking not only at feelings of alertness and associated attention performance, but also at brain activity and heart rate changes which can give a broader picture of what's happening.

We had participants complete a task where they watched a stream of 3-digit numbers-generally each number differed from the previous one, but every so often there would be a repetition (a bit like a quality control job on a production line). A vigilance task (i.e. sustained attention to rare target stimuli) such as this tends to be associated with a vigilance decrement (i.e. you perform more poorly at the task as time goes on). A previous paper indicated that chewing gum could improve performance on this type of task, but only after a certain amount of time performing it-that is, as eyes were starting to droop. In this study we looked at chewing gum on the same vigilance task, but this time we also measured electroencephalography (EEG) as well as heart rate, to see what physiological changes might accompany such effects. The vigilance decrement was probably enhanced by the fact that having the EEG equipment set up can take a longish while of sitting still (as anyone who has taken part in this study will attest to).

When participants chewed gum during the first stage of the vigilance task, they showed less of a post-baseline decrement on the vigilance test compared to those who did not chew gum (interestingly enough, this difference was still evident when further vigilance tasks were completed post-chewing). 

The EEG indicated that beta activity (which is associated with an alert state) was heightened at frontal and temporal areas following chewing gum; this effect was strongest straight after chewing, although it seemed to persist post-chewing. Furthermore, chewing gum was also associated with heightened heart rate, although this effect on heart rate seemed to dissipate quite quickly once chewing ended. It may be the case that central nervous system activity is a more likely explanation of ongoing effects of chewing than sympathetic nervous system activity (i.e. heart rate).

The study adds to a growing amount of evidence suggesting that chewing gum can enhance not only subjective alertness but also sustained attention. There has been some evidence that this can occur even in the absence of a vigilance decrement; I would speculate that this may have happened in the linked study as they used a task which I believe requires much more frequent responses to stimuli-this may reduce the extent of the decrement somewhat, compared to the vigilance task we used. (Consider running quality control on a production line where you have to spot the occasional mistake -vigilance- versus an assembly task whereby you have to continuously perform an operation on each passing piece of equipment -continuous performance. I think it's easier to tune out when you only have to do something every so often than when the default mode is responding to stimuli). 

Have I tested this on myself? I can recall attending one lecture where what I'll generously call a vigilance decrement (there was nodding involved) started to set in. This affliction was relieved to some extent by chewing some gum for a few minutes-thereby just about preventing an embarrassing collision of my head and the seat in front of me. Just don't go on an three-night, no-sleep road trip and blame me if anything goes wrong!

Allen, A.P., Jacob, T.J.C., Smith, A.P. (2014). Effects and after-effects of chewing gum on attention, heart rate, EEG and mood. Physiology & Behavior, 133, 244-251. 

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