Effects of smoked marijuana on human social behavior in small groups.

Six adult male research volunteers, in two groups of three subjects each, lived continuously in a residential laboratory for seven consecutive days. Subjects' behaviors, including social interaction and coaction, were continuously recorded. During the first part of the day (0945-1700), subjects remained in their private rooms doing work activities. During the remainder of the day (1700-2345), they had the option to socialize with the other subjects. Four cigarettes containing active marijuana (2.7% delta 9-THC w/w) or placebo were smoked daily: two during the work period, and two during the social access period. Active marijuana had no effect on the total amount of time that subjects spent in the social area. However, active marijuana changed the distribution of activity within the social area by decreasing the amount of time subjects spent engaging in verbal exchanges, i.e., interaction, while simultaneously increasing the amount of time that subjects engaged in the same activity, but in the absence of verbal exchanges, i.e., coaction.