"To the contrary, the warning labels backfired: they stimulated the nucleus accumbens, sometimes called the 'craving spot,' which lights up on f.M.R.I. whenever

"To the contrary, the warning labels backfired: they stimulated the nucleus accumbens, sometimes called the 'craving spot,' which lights up on f.M.R.I. whenever a person craves something" - maybe they were craving to be non-smokers.