The effect of smoking was limited to the posterior region and only involved the amplitudes of P300a (F1,208 = 4.7, p < .03) and P300b (F1,208 = 5.3, p < .02). As shown in Table 2, a recent history of cigarette smoking, in comparison to its absence, was associated with an amplitude reduction averaging 2.3 μV for P300a and 3.0 μV for P300b. Smoking had no effect on P300a (F1,208 = .1, p = .7) and P300b (F1,208 = 1.1, p =.2) amplitudes over the anterior region and did not change P300 latency over either region (anterior P300a: F1,208 = 1.3, p = .2; anterior P300b: F1,208 = .4, p = .5; posterior P300a: F1,208 = .6, p = .4; posterior P300b: F1,208 = .4, p = .5).
