ONE-TRIAL SIMULTANEOUS AND BACKWARD FEAR CONDITIONING AS REFLECTED IN CONDITIONED SUPPRESSION OF LICKING IN RATS

Groups of albino rats received 1 strictly simultaneous pairing of a 4 s auditory conditioned stimulus (CS) and a 4 s 1 mA shock unconditioned stimulus (US). Other groups received a backward pairing, in which the US began before the CS, or a forward pairing, in which the CS began before the US. Control groups received only the US or received both the CS and the US but widely separated in time. Later, the CS was presented while the rats licked a drinking tube for water and CS-elicited suppression of licking was taken as an index of the Pavlovian conditioned response (CR). Groups receiving a single forward or a single simultaneous pairing suppressed more than groups that had received a backward pairing; and the backward groups suppressed more than the control groups. It appears that excitatory fear conditioning, as reflected in conditioned suppression of licking in rats, can be produced in a single trial by backward and simultaneous conditioning procedures.