82 Fig. 2 Global SAPS and SANS scores after S-ketamine and DMT (mean scores ±standard deviation; n=9) Psychopharmacology (2008) 199:77–88 8]=9.71, p=0.017 for S-ketamine; false-alarm type: F[2, 7]= 12.56, p=0.007 for DMT and F[2, 7]=13.20, p=0.006 for S- ketamine; interaction: F[2, 7]=6.69, p=0.030 for DMT and F[2, 7] = 5.72, p = 0.041 for S-ketamine). The effect of condition was significant with S-ketamine (F[2, 7]=8.83, p=0.016) and approached significance with DMT (F[2, 7]= 3.66, p=0.091). The second ANOVA computed without the baseline data revealed a significant effect of the factors ISI (F [1, 8]=13.19, p=0.008) and false-alarm type (F[2, 7]=10.62, p=0.011) and a trend for the factor drug (F[1, 8]=4.14, p= 0.081). The simple interactions were not significant. How- ever, two higher-level interactions with the factor drug passed the significance level (drug×alarm type×ISI: F[2, 7] = 7.71, p = 0.022; drug × dose × ISI: F[1, 8] = 5.65, p = 0.049). According to the post-hoc tests, there were signifi- cantly less “BY” compared to “BX” (p=0.003) and “AY” (p=0.015) errors. To explore the drug effect on the utilization of contextual information, we analyzed the “BX” error rates by means of a separate ANOVA with the factors drug, dosage, and ISI, and we found significant effects of the Fig. 3 AX-CPT: missing and error rate in percent of subjects who completed all five conditions (short ISI=0.8 s, long ISI =4 s; means±standard errors of the mean; n=9)