Effects of tobacco smoking and gender on interhemispheric cognitive function: performance and confidence measures.

Cognitive function in tasks involving interhemispheric processing of verbal and spatial information was studied in 31 college students in a 2 x 2 factorial design with chronic smoking status [smoker (10+ cigarettes per day) versus non-smoker (no history of smoking)] and gender as the main between-subject factors. The subjects participated in two sessions on two consecutive days. The same task was repeated within the same session with a 15 min interval: smokers were tested before and after smoking whereas non-smokers rested during the interval. Dependent behavioral variables included those of performance (speed and accuracy) and confidence (low rate of non-responding). The verbal task yielded an expected female advantage, and smoking had the gender-specific effect of increasing both speed and accuracy more clearly in males. In addition, smoking decreased the rate of non-responding (increase confidence) in women, thereby affecting preferred strategies for problem solving by shifting the female pattern towards the male pattern. The spatial task, which probably involved a more perceptual, rather than cognitive, level of functioning, produced no clear effects of smoking and gender, and yielded some laterality effects. The acute within-subject smoking manipulation wherein, among smokers, the first test was preceded by 10+ h of deprivation, whereas the second repeated task was preceded by the smoking of a cigarette (i.e. deprivation followed by partial release) did not affect the behavioral measures. In conclusion, smoking had a gender-specific effect on cognitive function: it improved the performance of males in a verbal task and increased the subjective confidence of females thereby affecting the preferred cognitive strategies for problem solving.