Effects of a shelter on open-field activity of rats and mice were examined. Subjects were both sexes of Wistar-Imamichi/Iar and F344/DuCrj strain rats and BALB/c and C57BL/6 strain mice. They were individually tested in three situations in a random order:(1) a standard open field, where the subject was first placed in a start box at a corner of the field (forced situation: FO);(2) an open field with a shelter, where the shelter was used as the start box (free situation: FR); and (3) an open field with a shelter, where a start box was used (forced-free situation: FF). Both species were less active in the FR and FF situations than in the FO situation, indicating that the presence of a shelter suppressed open-field activity of the animals. Data did not support the thesis that a shelter provides security to animals. For example, a few rats in the FF situation did not enter the shelter, although they showed enough ambulation to reach it. Also, many mice in the FR and FF situations left it hastily or hesitated to enter it. Behavioral differences by species, strain, and sex were also discussed.
The present experiments were designed to test the effects of negative contingencies of CS and US on conditioned suppression of licking in rats under conditions where P (USICS)-P (USInoCS) pairs were. 50-.50, .25-.50, and 00-.50. The contingencies were manipulated by matching the session length in a Time-Matched (TM) condition, and by matching the number of USs in a Number-Matched (NM) condition. To assess conditioned inhibition, the retardation technique was used in Experiment 1 and the summation technique was used in Experiment 2. The two methods of manipulating contingencies did not affect conditioning differently. Additionally, clear evidence of conditioning of excitation was found under zero contingency (.50-.50). However, . 25-50 conditions yielded no evidence of conditioning, and the inhibition was conditioned under 00-.50 conditions. The results are discussed with reference to possible procedural artifacts and the Rescorla-Wagner model.
We recorded transient visual evoked potentials (VEPs) to three kinds of geometric figures (equilateral triangle. square, and circle). These three figures were of equal area, equal contour length, or equal ratio of contour length to area. They were presented monocularly below the fixation point (FP). Angular separation between FP and the figure was held constant. Transient visual evoked potentials (VEPs) were recorded monopolarly from seven electrodes around the occipital area of eight subjects. The grand average of the subtracted waves was obtained between the figure and blank (control) conditions. N1 (mean peak latency: 160 ms) and P2 (240 ms) waves were identified. ANOV As were conducted for latency and amplitude. For the N1 amplitude, the triangle evoked a significantly larger response than did the other two figures in all stimulus conditions. No significant difference was found between the square and the circle. A similar effect was obtained for the P2 amplitude, but it was not as remarkable as for the N1 amplitude. There was no significant effect of form on the N1 and P2 latencies.
The present study aimed to extract knowledge on both knowing of the meaning of symbols of fractions and linking it to problem situations. Fourth and fifth graders were interviewed individually. Three kinds of meanings of symbols were found; appropriate meaning, inappropriate meaning, and lack of meaning. Four kinds of ways of linking were identified; appropriate linking, linking by inappropriate fractional knowledge, linking by whole number concepts, and linking by quotient. It was found that the most important factor in judging magnitudes of fractions was not knowledge for the symbols of fractions but one for linking it to the problem situations.
The aim of this experiment is to study the effect of the length of the inter-food interval (IFI) on immediately following adjunctive drinking in rats, under variable time 112.5 s schedule. The U-shaped relation was found between the length of the IFI and the latency of immediately following licking. The animals began to drink earlier and stopped drinking earlier following intermediate IFI than following shorter or longer IFIs. No systematic relation was observed between the length of the IFI and the number of immediately following licking responses. It was suggested that under FT schedules in previous studies the expected length of the succeeding IFI affected the amount of drinking, whereas under the VT schedule of the present experiment the length of the preceding IFI affected the latency of drinking.
The purpose of this experiment was to investigate whether overshadowing occurred between two contextual stimuli (light and tone) in Pavlovian conditioning of rats. Thirty-two albino rats, randomly assigned to four groups, were individually placed in a chamber, in which light, tone or both served as contextual stimuli. A single electric shock (1mA, 2-s) was delivered to the floor during once-a-day 5 min sessions for 5 consecutive days (conditioning phase). The day after finishing-the conditioning phase, each was placed for 5 min in the chamber, and light or tone was presented as a contextual stimulus (test phase). The group of rats exposed to both stimuli during the conditioning sessions but to light only during the test session (LT/L) froze less frequently in the test phase than in the conditioning phase. The other three groups (LT/T, T/T, and L/L) froze in the test phase as frequently as in the conditioning phase. These results suggest that the tone overshadowed a light when both of them were presented together as contextual stimuli of conditioning.
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 90° 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.
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