The effect of varying the nicotine content of cigarettes on human smoking behaviour

9 subjects were given cigarettes to smoke containing 3 different amounts of nicotine. It was found that the larger the content of nicotine in the cigarettes offered the smaller was the number smoked during the 8-h period. A linear relationship between nicotine content and time to smoke a single cigaretts was found such that the more nicotine there was in a cigarette the longer a subject took to smoke it.