However, the ability to assess the intoxication due to marijuana was greatly affected by alcohol. The subjective intoxication produced by marijuana appears to be of a more subtle nature than that produced by alcohol. They are prepared to make a hasty response to a question rather than to spend more time to ensure a correct answer. This effect could be related to a risk-taking behaviour. The results with marijuana on the other hand suggested a slower and more careful approach to the problem, though as with alcohol, an increased error rate in responses was recorded.
Evidence is presented which suggests that marijuana produces periodic attentional lapses.
The results strongly suggest that the performance deficits and mood changes produced by alcohol are of a greater magnitude than those produced by marijuana. Recommendations for directions of further research are made.