The participants were 40 volunteer undergraduates, 20 non-smokers and 20 who reported smoking 15-20 cigarettes per day. The non-smokers were students of psychology who took part in the experiment as a course requirement. The smokers were recruited by advertisements placed in bars throughout the university. They received payment for their participation.
A microcomputer was used to generate two sorts of task. The monotonous task (M) was based on a video game. By pressing keys on the computer's keyboard the participant could direct the representation of a gun at a rapidly moving "tank" and could "destroy" it. Targets were presented once every 30 seconds on average. For the intellectually demanding task (D) the same apparatus was used to present problems in mental arithmetic. These were of the form a + b - c = ? where a, b, and c were 3-digit numbers. Subjects responded by typing in their answer and the computer then presented a new problem.
All participants were given a 30-minute session on task M and the number of "hits" scored by each was recorded. A 30-minute session on task D followed immediately and the number of correct answers was recorded. Smokers were encouraged to smoke if they wanted to when performing these tasks.
The mean scores of the participants are presented below:
|Task M (hits)||Task D (correct answers)|
Two t-tests were used to evaluate these results. There was no significant difference in the scores for task M (t = 1.35, df = 38) but the two groups differed reliably on task D (t = 2.70, df = 38, p < 0.05). It was noted that smokers tended to respond rather slowly on task D attempting a mean of only 10.2 problems. Non-smokers attempted a mean of 26.3 problems. Analysis showed these scores to differ significantly, t = 2.85, df = 38, p < 0.05.
The fact that scores were much lower on task D than on task M confirms that we were successful in creating tasks that differed in the intellectual demands they made. The inferiority of the smokers (significant on task D) suggests that they are mistaken in their belief that smoking helps them to perform such tasks. The subsidiary finding that smokers were able to attempt fewer task-D problems than were non-smokers adds weight to our conclusion that smoking hinders performance.
Our general conclusion, therefore, is that smokers deceived themselves in the answers they gave to our questionnaire and that smoking does not aid concentration. We can accept however that smoking has differential effects on the two types of task having less of a deleterious effect on monotonous than on demanding tasks.