Habitual smokers smoked either nicotine-free cigarettes or cigarettes
containing a known amount of nicotine and then engaged in a free-recall
task. Nicotine subjects recalled significantly fewer words on a 75-item
list during three successive trials of immediate recall than did
nicotine-free subjects. Contrary to expectations, the superiority of the
nonnicotine group persisted over two days. The two groups displayed
comparable organizational activity (indexed by category clustering).