The present study examined the effects of food-deprivation and food-reward on the behavior of rats in the eight-arm radial maze. In the free-choice training, all of the four groups of rats, deprived-and-rewarded (DR), deprived-and-unrewarded (DU), nondeprived-and-rewarded (NR), and nondeprived-and-unrewarded (NU), made choice more efficiently than chance level, but the rats in DR made fewer errors than the other three groups. As for the choice patterns, all the groups showed the tendency to choose the arms 900 apart from the arms chosen just before. This tendency was shown most significantly in DR. These findings suggest that the efficient arm-choice behavior of rats is not determined by a simple effect of either food-deprivation or food-reward but by an interactive effect of these two factors.

Nonreinforced exposure to a stimulus before conditioning reliably retards the acquisition of conditioned responding to that stimulus. Several experiments have found that this "latent inhibition effect" (Lubow, 1973) is attenuated if the stimulus (target) is preexposed in compound with a second stimulus (distractor) (e.g., Best, Gemberling, & Johnson, 1979;Honey & Hall, 1988;Lubow, Schnur, & Rifkin, 1976;Matzel, Schactman, & Miller, 1988; but see also, e.g., Mercier & Baker, 1985;Rudy, Krauter, & Gaffuri, 1976, for negative findings). These results seem to require an account which assumes some competing process between the target and the distractor during preexposure, for example reciprocal overshadowing in association with inattentional response (Lubow, 1989;Lubow, Weiner, & Schnur, 1981) or competition for access to short-term memory (Wagner, 1978(Wagner, , 1981.Distractor effect on the latent inhibition of conditioned flavor aversion in rats 1 KIYOSHI ISHII Department of Psychology, School of Letters, Nagoya University, Chikusa-ku, Nagoya 464-8601, Japan YASUAKI HAGA Department of Psychology, School of Letters, Nagoya University, Chikusa-ku, Nagoya 464-8601, Japan YUTAKA HISHIMURA Department of Psychology, Faculty of Humanities, Niigata University, Ikarashi, Niigata 950-2181, Japan Abstract: Using a conditioned flavor aversion procedure with rats as subjects, the effect of the addition of a distractor stimulus on the magnitude of the latent inhibition effect was examined. Experiment 1 showed that latent inhibition to vinegar was attenuated by the addition of sucrose during preexposure. On the other hand, sucrose added during conditioning to vinegar did not attenuate latent inhibition. It was also found that the degree of latent inhibition to the vinegar-sucrose compound solution was less when vinegar alone was preexposed (i.e., when sucrose was added only during conditioning) than when the compound solution was preexposed (i.e., when sucrose was added both during preexposure and during conditioning). Experiment 2 gave similar results but with sucrose assigned as the target flavor and vinegar as the distractor. These findings are in full agreement with the generalization decrement account of latent inhibition.

Rats were trained with three delay-interpolated tasks in a radial-arm maze. The tasks differed in the post-delay bait conditions. When every arm was baited in the post-delay free choices (Task E8B), rats made adjacent-arm choices frequently. When only the four arms unvisited in the pre-delay forced choices were baited after delay (Task U4B), rats chose unvisited arms preferentially, with frequent arm investigations. When four quasi-randomly selected arms were baited after delay (Task R4B), rats did not choose adjacent arms as frequently as the rats in Task E8B did, and made fewer arm investigations. These results indicate that the rats developed different arm-choice strategies in accordance with tasks. As for the effects of rewarding, post-delay choice behavior was not affected by the pre-delay bait conditions.

Using the conditioned taste aversion paradigm, two experiments were conducted to examine the effects of the interval between preexposure and test and that between conditioning and test on the magnitude of latent inhibition. Experiment 1 revealed that the degree of latent inhibition was attenuated when rats were given a 21-day interval between preexposure and test. It was also found that this attenuation was more marked in subjects which were given conditioning immediately after preexposure than those which were conditioned shortly before the test. Retention interval between preexposure and test was reduced to 12 days in Experiment 2, and exactly the same pattern of results as those found in Experiment 1 was obtained. These findings suggest that the memory of conditioning as well as that of preexposure decreases its retrievability after a long retention interval, although the former is more retainable than the latter.

The present study compared rats' behavioral changes on three tasks on the radial‐arm maze. In the free‐choice task (0Fo/8Fr; no forced choice/eight free choices), rats performed efficiently with the simple response pattern of sequential adjacent‐arm choices. In the two forced‐choice tasks (3Fo/5Fr and 5Fo/3Fr), rats performed as efficiently as 0Fo/8Fr but showed no particular response patterns. The frequency of arm investigation was the highest in 5Fo/3Fr, and was higher in 3Fo/5Fr than in 0Fo/8Fr. The probability of correct rejection, avoiding re‐entry to visited arms after investigation, was also higher in 3Fo/5Fr and 5Fo/3Fr than in 0Fo/8Fr. These results suggest that the rats could adjust their behavior to the task demands.