ネズミの自発的交替現象と飢餓動因との関係

抄録

Two groups of rats were run a T-maze with reward in both goal-boxes. Group LD under three hr. food deprivation was given two series of 11 trails a day for six days. The inter-trial interval used was 20″ for one series and 60″ for the other. The order fo the two series was counterbalanced from day to day. Group HD was the same as Group LD except that the deprivation was 23 hrs.
Per cent alternation as a joint function of drive levels, inter-trial intervals and the nember of trail days was shown in Table 1 (see Text) and the analysis of it in Table 2. The effect of drive strength itself was lacking but the triple interaction between drive, intervals and days was significant. A closer analysis of the data (Fig. 1) revealed that the alternation tendency in Group LD was little affected by the interval but rather by the number of trials, while both effects were observed in Group HD.
As the intra-day series of trials were spaced one hr. and the first daily runs were separated 24 hr., alternation percentages for the inter-trial intervals of one hr. and 24 hrs. could be computed (Tables 4, and 5, and Fig. 2). Decay of the alternation tendency appeared but the effect of drive was again nil. As the decay of alternation does not necessarily indicate the growth of position preference, number of turns to preferred side was measured throughout 12 series (Fig. 3). The preferred side was defined as the side which the rat chose more than half of the total trials. The growth of position preference was clearly shown although drive strength was ineffective (Table 6).
The presrnt results did not agree with either Elliott nor Fujita both of which proved the negative relationship between hunger drive strength and alternation behavior. However the weakness in experimental design of the two studies was pointed. That is, five choice-alleys of Elliott's apparatus would not be behaviorally equivalent in that less energy was needed for turns to the middle alleys compared with others ; the time interval between 22 massed trials was not the same among the three groups of different drive lavels in Fujita's study. These points could explain their results irrespective of drive differential.
Previous inhibition theories of alternation behavior expect the growth of alternation with the increase of discriminative ability in the organism. As the hungrier rat would have a greater ability to discriminate, its alternation tendency would be greater. However the same rat would acquire a greater SER increment with a reinforcement and this in turn would reduce alternation. These two factors would work against each other and thus the effect of drive level on alternation would not be realized. However as the high-drive rat would be more sensitive to the inter-trial interval difference than the low-drive rat because of its greater ability to discriminate, the effect of the time interval on alternation would be greater in the former. These were what was obtained in the present study.
The decay of alternation throughout trials could not be explained by previous theories because the daily blocks of trials were spaced as long as 23 hrs. The author agreed with the conditioned-inhibition theory of Calvin et al. but believes SIR is a learned negative drive. It was hypothesized that negative drive decrease alternation and facilitates the pre-learned or innate position preference in the organism. This could explain not only the present results but also less than 50% alternation which was often observed, and especially Maier's response fixation. The fact that negative drive of electric shock decreased alternetion as shown by Iwahara, Soeda and Iwahara, was in complete accordance with the hypothesis.