It is not just the external stimulu-sconstellation characteristics such as the form, the brightness of the figure, and the distance from the figure to the point which influences the light threshold of a small test patch projected at various points inside a figure. In the compound figures whose appearance changes according to the subject's attitude in the grasping of the forms, it is also influenced by the attitude.
Firstly with the three kinds of compound figures used, the changes of the light threshold values inside these figures were examined under a variety of the subject's attitudes.
In Experiment I and II, the reversible figure-ground pattern of a large and a small concentric regular square (Fig. 2) was used and the following two kinds of attitudes were adopted. A₁: S made an attempt to grasp the small square as the “figure”, and A₂: to grasp the space between both ones likewise.
In Experiment III and IV, the reversible roof-shaped depth figure (Fig. 3) was used and the following two kinds of attitudes were adopted. A₁:S made an attempt to grasp the left parallelogram as situated in the foreground, and A₂: to grasp the right one likewise.
In Experiment V and VI, where an overlapping figure consisting of a regular square and a regular triangle (Fig. 4) was used, the following three kinds of attitudes were adopted. A₁:S made an attempt to grasp the square as the “figure”, A₂: to grasp the small overlapped triangle as such, and A₃: to grasp the large triangle likewise.
The results of these experiments (Table 1-6) seemed to ascertain evidence of some influence of the attitude on the light threshold. As for the results of Experiment V and VI (Table 5 and 6), the manner and the extent of the influence of the attitude on the light threshold was analyzed quantitatively according to Yokose's potential theory.
The results of these quantitative analyses were as follows.
(1) The changes of the light threshold values inside the compound figures were correlated to the weighted sums of potentials (the field strength) of its constituent forms.
(2) The influence of the attitude was expressed as the weighting coefficients of potentials (Table 3 and 9).
(3) The weighting coefficients of potentials of each form increased when it was grasped as the “figure”.

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In many investigations of reaction time reported so far, results have been fitted by an equation of the form
t_i=-alogp_i+b (1)
where t_i is the disjunctive reaction time for the stimulus alternative i, a and b are constants and p_i is the probability of occurrence of the alternative i. It appears that, however, the reaction time is determined by the subject's expectancy for the toccurrence of the stimulus alternative, so we assume that the above relation is better represented by the equation
t_i=-alogp′_i+b (2)
where p′_i is the subjective probability for the occurrence of the alternative i. The characteristics of p′_i have not yet been fully investigated.
It is known that the reaction time for the stimulus sequence is shorter when
(1) the subjective probability approaches to the corresponding actual probability in the sequence, and
(2) the stimulus sequence is statistically redundant.
Eased on the previous studies, we assume that the subjective probability for each stimulus in the sequence consists of several weighted terms; i.e, a term which is equally weighted for all stimuli, a term related to the frequency of each stimulus, a term related to the conditional probability of the stimulus when we regard the sequence as a simple Markoff process, a term related to the conditional probability of the stimulus when we regard the sequence as a double Markoff process, and so on, Thus a formula was given as follows;
p″_{i, m}=w₀⋅1/n+^mΣ_k=0w_k+1⋅p_{i, k}
where, p″_{i, m} means the subjective probability for the stimulus i when we take into account up to the m-th conditional probabilities, and w's mean weights for the terms mentioned above.
Using this subjective probability a new formula representing the mean reaction time was obtained. We called this new formula a new model, and compared it with formula (1), the old model.
Under several experimental conditions, the weights of subjective probability were examined. Ss were asked to press the corresponding key to each letter in the given sequence.
Experiment 1. A random sequence of letter was used as stimuli. Parameters of formula (1), a and b, were determined for each subject.
Experiment 2. A sequence was used in which letters occurred independently but their frequency was unbalanced. Weights in formula (3), w₀ and w_1-, were determined for each subject.
Experiment 3. The sequence was a simple Markoff process. The weight w_2- in formula (3) was determined for each subject.
Experiment 4. The sequence was a double Markoff process. The weight w_3- in formula (3) was determined for each subject.
Experiment 5. The same procedure as in Exp. 1 was used, and parameters a and b were determined again.
All the results obtained for different subjects under different experimental conditions showed better fit to the new model than to the old model. In Exp. 4, the weights w_3- of the double Markoff process were 0. It seems that the subject found it difficult to reach the state of perfect learning of objective probabilities, when the order of statistical dependency in the stimulus sequence was high. In other words, there was a limit in the learning of redundancy.
We have introduced the concept of the differential contribution of various orders of sequential dependency of stimuli to the construction of the subjective probability in relation to the problem of reaction time. There are still many problems left to

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The present study was designed to investigate the context effect on loudness judgment. Exp. 1 was done in just the same way as Garner did in 1954. Ss were asked to make half loudness judgment. The variable stimulus series were 55-65dB, 65-75dB and 75-85dB 1000Hz pure tone, each with 90dB standard tone. 5 Ss for each series. Here the paint of half loudness of the standard was almost the midpoint of each stimulus series. This is the same result as Garners, and shows that half loudness judgment depends on the stimulus context (Table 1). In Exp. 2, the noise in the electric car was used as a stimulus and stimulus series were 50-75dB, 60-85dB, 70-95dB and 45-95dB. 5 Ss for each series were instructed to judge absolutely the loudness using 7 categories. A clear context effect was found as shown in Fig. 1. The results of Exp. 1 and 2 indicate that there evidently exists the context effect on loudness judgment.
The question is why such context effect appears. Helson says in his Adaptation-level theory that the judgments are made on the basis of sensory character and that the shifts in judgment reflect the change in sensation. On the other hand, Stevens insists that the context effect appears as a result of semantic limitation of verbal reports. Therefore in Exp. 3 reaction time was used as an index of loudness. White noise (w. n.) and band noise (b. n.; center frequency 4000Hz) were used as stimuli and Ss were instructed to respond only to white noise by releasing the key as soon as they heard the noise. The stimulus series were 60-80dB w. n. & 50-70dB b. n., 70-90dB w. n. & 60-80dB b. n., 80-100dB w. n. & 70-90dB b. n. and 60-100dB w. n. & 50-90dB b. n. 5 Ss for each series. The result showed a clear context effect between sound pressure level and reaction time as shown in Fig. 3 and Table 2.
It is quite remarkable that there exists the context effect in the experiment using reaction time which is quite free from the semantic effect or Ss' intentional modification. Although reaction time cannot be said to represent the real value of sensation, and there is a possibility that reaction time may be influenced by motor effect, this result may be said to be a noteworthy one since it suggests that the context effect is not to be entirely attributed to the semantic effect as Stevens insists, but may reflect the change in sensory character.

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The function of wordness of Japanese two-letter syllables (corresponding to English CVC trigrams) was investigated. 111 Ss were forced to classify 200 syllables into one of seven parts of speech (noun, verb, auxiliary verb, adjective, adverb, particle and conjunction). When one part of speech was choiced by more than 56 Ss, we decided the syllable as that part of speech type. There were 64 noun type syllables, 11 verb type, 2 auxiliary verb type, one adjective type, and 2 mixed type (each syllable had a homonym belonging to the different parts of speech, noun and verb). The other 120 syllables could not be classified into a particular part of speech, so we called them as an indefinite type. The classification is printed in Table 5, column 13th.
To discriminate the difference of the function of the parts of speech type and the indefinite type, two experiments were run. 3 minutes after classifying task, 111 Ss were instructed to recall as many syllables as possible which were classified into the seven parts of speech. In this incidental recall experiment, the mean number of Ss per syllable who recalled the parts of speech type syllables and the indefinite type syllables, were 7.38 and 2.93 respectively. (Exp. 2, Table 1)
Exp. 3 was paired-associate learning. Stimuli were two place digits and responses were two-letter syllables. The two lists used are shown in Table 2. Each list was composed of 8 pairs, four of which were the parts of speech type and the other four were the indefinite type, and in each list, syllables were controlled by non-association value and frequency of occurrence. The mean number of correct anticipation in 20 trials for the parts of speech type and the indefinite type were 16.2 and 12.7 in list A, 14.2 and 11.8 in list B. (Table 2) Each experiment proved that syllables belonging to the parts of speech type were significantly easier to learn than the indefinite type syllables.
The mode of number of Ss who choiced one of the parts of speech of a syllable was counted through the 200 syllables, and it was called “Mode”. The Spearman's r's between the Mode and other 11 scales (Imae, 1966), and between the Mode and number of Ss who recalled incidentally the syllable were described in Table 4.
The Mode highly correlates to ease of learning and rated meaningfulness, and the mean number of Ss recalled highly correlates to the Mode and the ease of learning.
The 64 noun type syllables were divided by 47 Ss into an abstract noun type and a concrete noun type. When 2/3 of Ss selected one alternative, we decided the syllable as the abstract noun type or the concrete noun type, and the other indefinite, and the number of syllables of each type were 19, 31, and 14 respectively. When these syllables were controlled by non-association value and ease of learning, the mean number of Ss incidentally recalled per syllable were more in the concrete noun type syllables than in the abstract noun, (Table 3) This is consisted with the recent studies on the noun abstractness.

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