king thickening group， the non-smoking plaque group， and the non-smoking control group (P>0.05). The smoking thickening group and the smoking plaque group had significantly higher number of cigarette selections and total number of selections than the non-smoking thickening group and the non-smoking plaque group (F=362.377，28.916;t=5.92-26.67;P<0.05). The high and moderate nicotine-depen-

    dence groups had a significantly higher total number of cigarette selections than the mild nicotine-depen-

    dence group ......