“…For instance, Ramsay and colleagues found that almost twice as many acquisition trials were required lo reach the criterion of learning when participants received 30% N 2 0 rather than a placebo gas (for converging evidence, see Mewaldt, Ghoneim, Korttila, & Petersen, 1988). Nitrous oxide also impairs performance on recall tests (Dwyer, Bennett, Eger, & Heilbron, 1992;File et al, 1993;Ghoneim et al;Mewaldt et al;Ramsay et al) and on recognition tests (Block, Ghoneim, Hinrichs, ct al. ;Dwyer ct al.…”