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In one study , smokers and nonsmokers were asked to note pauses in the sweep hand of a clock . Researchers based their conclusions on a study where smokers and nonsmokers were instructed to read materials about a stop-smoking aid , while another group read materials on quitting smoking without assistance . In this study , smokers and nonsmokers were annually screened for lung cancer between 1996 to 1998 using LDCT . For example , postmortem studies comparing the brains of human smokers and nonsmokers found that lifelong smokers had far more nicotine receptors than nonsmokers did in key brain regions . In one study , platelet sensitivity to the anti-aggregatory prostaglandins before , during , and after ETS exposure in smokers and nonsmokers was measured ( Sinzinger and Kefalides , 1982 ) . Between 11 and 14 , the belief that cigarettes are addicting decreased , but between the ages of 15 and 18 and between ages 19 and 24 , both smokers and nonsmokers increased their belief that cigarettes are addicting .