The effects of nitrous oxide at different subanaesthetic concentrations were examined in twelve subjects. Subjective intoxication and eight mood variables were measured using magnitude estimation, and objective performance was tested with memory and arithmetic tasks. For most variables, dose-response curves showed progressively larger effects as dose increased. At concentrations below 20 percent, changes were very slight. The results are compared with similar data from an alcohol experiment.
Subjective intoxication from nitrous oxide increases regularly and pronouncedly with higher doses, as measured by magnitude estimation. Both the intoxicated subjects' own estimates and observers' ratings showed this pattern. Objective performance changes followed the same general trend but were much less pronounced. The authors concluded that subjective scaling methods are well suited for measuring drug-induced changes in subjective variables.