Я погуглил, и это таки цитата из абстракта:

"Effects of chewing gum on cognitive function, mood and physiology in stressed and non-stressed volunteers."

"RESULTS: Chewing gum was associated with greater alertness and a more positive mood. Reaction times were quicker in the gum condition, and this effect became bigger as the task became more difficult. Chewing gum also improved selective and sustained attention. Heart rate and cortisol levels were higher when chewing which confirms the alerting effect of chewing gum."

https://www.ncbi.nlm.nih.gov/pubmed/20132649

Или вот ещё, другое:

"Effects of chewing on cognitive processing speed"

"Behavioral results showed that mean reaction time was significantly decreased during chewing condition, regardless of speed-accuracy trade-off, although there were no significant changes in behavioral effects (both alerting and conflict effects)."

http://www.sciencedirect.com/science/article/pii/S027826261200173X

Так что никаких шуток, оказывается )