Gummed-up memory: chewing gum impairs short-term recall.

You can ask your doctor to compare this one to the mastication induced arousal one I posted about earlier.
From http://io9.com/5905964/chewing-gum-can-mess-with-your-mind
comes this suggestion.
So what might explain these contradictory results? The scientists at Cardiff noted they used flavorless gum, while the past study used minty gum. Flavor might make a key difference — the brain might better remember tasks linked with pleasant experiences such as nice flavors.
http://www.ncbi.nlm.nih.gov/pubmed/22150606?dopt=Abstract

Abstract

Several studies have suggested that short-term memory is generally improved by chewing gum. However, we report the first studies to show that chewing gum impairs short-term memory for both item order and item identity. Experiment 1 showed that chewing gum reduces serial recall of letter lists. Experiment 2 indicated that chewing does not simply disrupt vocal-articulatory planning required for order retention: Chewing equally impairs a matched task that required retention of list item identity. Experiment 3 demonstrated that manual tapping produces a similar pattern of impairment to that of chewing gum. These results clearly qualify the assertion that chewing gum improves short-term memory. They also pose a problem for short-term memory theories asserting that forgetting is based on domain-specific interference given that chewing does not interfere with verbal memory any more than tapping. It is suggested that tapping and chewing reduce the general capacity to process sequences.