There is a social stigma attached to chewing gum. This was disproved by an experiment conducted by Beldent Gum Maker at Buenos Aires Museum of Modern Art with sets of identical twins. Maybe it got to do with the fact that the act of chewing gum reduces salivary cortisol and alleviates negative mood as in another clinical study (Scholey, et al., 2009).
Scholey, A., Haskell, C., Robertson, B., Kennedy, D., Milne, A. & Wetherell, M. (2009). Chewing gum alleviates negative mood and reduces cortisol during acute laboratory psychological stress. Physiology & Behavior,97(3–4), 304-312.