The Gaussian surrogate-date procedure was applied to the measurement o
f the effect of cigarette smoking on the dimensional complexity of nor
mal, resting EEG. Evidence of significant nonlinearity in the EEG was
obtained, replicating previous results. However, unlike EEG dimensiona
l complexity, EEG nonlinearity (difference between original and surrog
ate data) was not affected by smoking. This indicates that, under rest
ing conditions, smoking/nicotine may have a modulating effect on input
from the reticular activating system, with such input having a global
, linearizing effect on cortical dynamics. Nonlinear dynamics resultin
g from intracortical processes appear not to be affected.