Figure 8. Effects of severity of past cocaine use on cocaine choice.

(A) Distribution of individual preferences regardless of past cocaine use. Only 16 individuals out of a total of 184 rats tested in the choice procedure preferred cocaine over water sweetened with saccharin (closed circles). (B) Histograms represent the frequency of cocaine-preferring individuals (i.e., cocaine choices >50% of completed trials over the last 3 stable testing sessions) as a function of past cocaine use (i.e., amount of self-administered cocaine prior to choice testing). (C) Bars represent mean (± s.e.m.) preference over the last 3 stable testing sessions as a function of past cocaine use. For other details, see Materials and Methods, and legend of Figure 3. #, different from the indifference level (P<0.05, t-test); *, different from the lowest level of severity (P<0.01, Fisher's LSD test following a one-way ANOVA).