Learning to Discriminate between Alcohol and Nondrug Condition

Abstract

In the present experiment, food was located in one arm of a T-maze on days when hungry rats had been given alcohol and in the other arm on placebo days. Prior techniques for demonstrating discrimination between drug and placebo conditions (Conger, 1951; Overton, 1964) required use of painful electric shock. Method.-Ss were 8 adult, female, albino rats, fed 12 gm. Purina chow daily. Shortly before feeding, they were given 4 trials, at intervals of 2 min., in a T-maze with a 24-in. stem, 12-in. arms, and 4-in. width of the passageways. Five minutes before the first daily trial they were injected intraperitoneally wirh ethyl alcohol ( 1200 mg/kg in a 10% solution) or with placebo (isotonic saline, 15 ml/kg). Two successive days under one condition were followed by 2 days under the other condition, and this double alternation continued for 48 days. The correct choice (one arm on alcohol days, the other on placebo days) was rewarded by 4 food pellets (45 mg. each). Rerultf and concla~ions.-In 4 blocks of 12 days, percentages of correct choices on the first trial of the day were successively 58%, 6096, 7993, and 8896, averaging together scores for the 4 Ss which learned to discriminate between the alcohol and placebo conditions. During the last 24 days each of these Ss significantly preferred the correct arm (sign test, $J < .01) on the first daily trial (22, 20, 19, and 19 out of 24); on Trials 2 to 4 they averaged 92% correct choice. On alcohol days the food was in the right-hand arm for 2 Ss and in the left-hand arm for the other 2 Ss. When under alcohol, Ss showed less hesitation and thus shorter running times than on placebo days, but there was little difference in percentage of correct choices. One of the remaining 4 Ss died during training. The ocher 3 Ss showed persistent position preferences, so that their performance did not differ significantly from 50% correct choice on the first daily trial. When the preferred arm was incorrect, all 4 trials of the day were often unrewarded; therefore, additional trials under this condition, early in training, might have induced these 3 Ss to select the non-preferred arm and learn the discrimination.