An attempt was made to measure reaction time in the discrimination of two pure tones as a function of pitch difference and to examine Takada's hypothesis proposed from the view point of information theory (Jap. Psychol. Res. 1960). The subject was instructed to press the telegraph key on the right hand as soon as possible, if he judged that the second of the two successive tones was higher in pitch than the first, and to press the left key if he judged lower. Fig. 1 shows a block diagram of the apparatus used to present the stimuli and to measure reaction time. Reaction time was defined as the time between the on-set of the second tone and the key-pressing response. The frequency of the standard tone was constantly 1100cps. throughout all experiments, while that of the comparison tone was varied as described later. The loudness of tones was approximately 70phon. Four subjects were used.
In the preliminary experiment, the effects of the tonal duration and the interstimulus interval on reaction time were examined using five different durations, ranging from 250 to 2000msec, and six intervals from 60 to 2000msec. The frequencies of the comparison tones were 1070 and 1130cps. The mean reaction times obtained in this experiment are shown in Fig. 3 as a function of inter-stimulus intervals. Each line indicates the condition of duration.
In the main experiment, twelve comparison tones were used, frequency of which varied from 310 to 2370cps in 12 steps, excluding the same frequency as the standard. From the results of the preliminary experiment, 0.5sec duration of tones and 1.0sec inter-stimulus interval were adopted. The results of this experiment are shown in Fig. 5 in which each point plotted represents the mean of eighty reaction times (4 subjects×20 repetitions) obtained for each condition of the transmitted information which was calculated from the absolute pitch-differences in logarithmic mel, using the following equation:
I_t=log₂M-log₂Δm (1)
where I_t is the amount of information transmitted by stimulus patterns consisting of two tones, M is the maximum range of pitch in mel and Δm is the pitch difference in mel between the standard and the comparison tones. The lines in Fig. 5 indicate the predicted values from the equation,
Rt=aI_t+b (2)
where Rt is the reaction time in millisecond, and a and b are constants. The analysis of variance shown in Table 1 indicates that the effects of frequencies (F), session (S), and subjects (Ss), and interactions, Ss×S, Ss×HL (Higher versus Lower groups of tones as compared with standard), F×Ss×HL and Ss×HL×S were all statistically significant beyond the 1% level, while F×S was significant beyond the 5% level. The practice effect was shown only between the first and the later three sessions, in which the reaction time was shorter than in the beginning. The average rate of information processing was calculated to be 22.7bits/sec from the obtained data by the least square method. This value is of the same level as those of Takada and some others, but differs from that of Henmon.
In the supplementary experiment, the simple reaction time without discrimination task was measured under the same condition as the preliminary experiment. The effects of duration and interval in this experiment show the same trend as the preliminary experiment.
The results of this study supported Takada's hypothesis on the information processing in discrimination.

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A model of the learning process having a serial position effect was constructed. By this model we can carry out two analyses, one being an analysis of the learning process of each item in a list in terms of the learning speed and the initial learning probability, the other being an analysis of the serial position effect appearing in the initial learning probabilities in terms of pro- and retro-active inhibitions and of forgetting.
A free-recall experiment and a serialanticipation experiment were carried out in order to verify this model. Almost random numbers of two to six digits and nonsense syllables of two Japanese letters were used as material. Each list is composed of 5, 10 or 20 items of these numbers or syllables, and each subject participated in only one experiment per day.
The learning speed and the initial learning probability based on this model were obtained from the results of each experiment for each subject. The learning speed was found to be independent of position in the list, as shown in Fig. 1, 4 and 5. Moreover, by the statistical test of significance, it was also found that the learning speed is independent of the difficulty of the items, the length of lists and the kind of material. On the other hand, the initial learning probability was the Ushaped curve with respect to the position in the list, as shown in Fig. 1, 4 and 5. This tendency was analyzed by our model and we arrived at the following conclusions:
1, Pro- and retro-active inhibitions remain constant throughout all the experiments for each subject.
2. The forgetting rate does not depend on the difficulty of the item but decreases as the list lengthens.
3. The amount of immediate memory does not depend on the length of the list but decreases as the items increase in difficulty.
The curves in Fig. 2, 3, 4 and 5 were obtained by fitting our model to the results of the above experiments. By plotting the amount of immediate memory in logarithmic scale against the number of digits, it was found that the relation is linear, as shown in Fig. 6. The same relation is found between the forgetting rate in logarithmic scale and the logarithm of the length of lists, as shown in Fig. 7. By considering those relations, our model was extended so as to cover every case which ranges, over 2 to 6 digits per item and 5 to 20 items per list, and it was found that after two experiments with differing numbers of digits in the items and lists of different lengths are carried out, all the cases mentioned above can be predicted by our model.
Finally, it was observed that random numbers are better than nonsense syllables as learning material.

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In the previous papers, two behavioral features, the decrement of behavior variability and the facilitation of running response, were found (1) during the reconditioning period following extinction, (2) under partial reinforcement and (3) to the positive stimulus during succesive discrimination in the semicircular maze. These experiments also showed that these features were only found when reinforcement was presented after or between nonreinforcements. When only reinforcement or nonreinforcement was presented continuously, these features were not found. The present experiment was so designed as to examine this interaction effect of reinforcement and nonreinforcement, which we call induction, by use of the repeated conditioning-extinction procedure and to compare this result with those obtained in the three previous experiments.
After exploration, pretraining and preconditioning, twelve rats (the experimental group, i.e. the repeated extinction-conditioning group) were daily given 40 successive trials, the first half being continuous nonreinforcement and the second half being continuous reinforcement for 5 days in a semicircular maze which had a spacious field and eight goal boxes. An extinction period of 60 trials followed in the next day. Other twelve rats (control group) were treated by the same procedure, but they were daily given only 20 reinforcements for 5 days.
The results were:
1. During the repeated extinction-conditioning period, behavior variability (in three different measures) observed during the daily reinforced period of the experimental group progressively decreased with days until it reached lower than the chance level. However, this phenomenon was not found in the nonreinforced period of the experimental group as well as in the reinforced period of the control group.
2. The running responses measured in terms of running time, the number of sectione traversed and the number of pushing of the doors at the goal-boxes reduced in the same manner as behavior variability did. That is, the values of these three measures reduced more in the reinforced period of the experimental group than in the nonreinforced period of this group and in the reinforced period of the control group.
3. With reference to the similar results found in our three previous experiments, it might be concluded that the above two features were produced by the interaction effects of reinforcement and nonreinforcement.
4. Although the running responses during the nonreinforced period of the experimental group were similar to the phenomena revealing in a continuous extinction on each day, these changes progressively disappeared with repetitions of extinction-conditioning procedure.
5. During the extinction of 60 trials, behavior variability increased above chance and in the running responses a greater resistance to extinction was found than was when the rat was treated under partial reinforcement in our previous experiment. These results (4 & 5) may indicate that the order and the number of reinfocrcement and nonreinforcement were important factors in this kind of phenomena.

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Various factors have been found to determine the difficulty of paired-associate learning. The present study was designed to examine the relationships among these factors and the difficulty of learning by a factor-analytical method.
Forty common nouns were used and four experiments were conducted, as follows: (1) Paired-associate learning and retention: Ss learned two lists of 10 pairs of nouns for five trials and were tested by anticipation method after one week. (2) Free association test: Ss were given a written association task to all stimulus nouns. (3) Restricted association test: Ss were asked to give sensory impressions to the same nouns. (4) Semantic differential: Ss rated the connotative meaning of each noun on 20 semantic scales. Ss were 280 undergraduate students in all.
The centroid method of factor analysis and orthogonal rotation of axis were applied to the correlation matrix based on 15 measures for 20 paired-associates which were obtained from the four tests; four factors were extracted.
The variables positively loaded with Factor I were difficulty of learning (during acquisition), amount of retention, differences of rating scores between stimulus items (S) and response items (R), and associative overlap between S and R. Thus Factor I was interpreted as “similarity between S and R”. Factor II had high positive loadings on rating deviation and associative score of R, arid Factor III on rating deviation and associative score of S; hence these two factors were considered as “meaningfulness of either S or R”. Because of its high positive loadings on difficulty of learning, amount of retention, differences of rating scores between S and R, associative overlap between S and R, and associative overlap of sensory impressions between S and R, Factor IV was interpreted as “associative similarity between S and R”. Results showed that both associative and connotative similarities are major factors which mediate between S and R in paired-associate learning. Meaningfulness of either S or R had no significant relationship to difficulty of learning as well as to amount of retention in this study, but these findings are of course restricted within the present experimental setup and materials.

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