This study investigated the effects of self-awakening on daytime sleepiness. Eleven undergraduate and graduate students without the habit of self-awakening participated. They were instructed to follow their usual sleep-wake schedule at home during the experimental weeks and were required to awaken at their usual time by themselves every morning for one week without the aid of an alarm (self-awakening condition) or in response to a telephone call from the experimenter every morning for another one week (forced-awakening condition). On the last day of each week, daytime tests were conducted in the laboratory. The participants would arrive at the laboratory 2 h after awakening, and 1 h later, they performed the auditory simple reaction time task, the digit-symbol substitution task, the letter cancellation test, and the multiple sleep latency test, and assessment of sleepiness, fatigue, comfort, and work motivation every 2 h. In the week when the participants underwent the self-awakening condition, self-awakening had a higher success rate (82%) than failure rate (18%) on the seventh day. In comparison with forced-awakening, self-awakening resulted in an improvement in subjective fatigue; however, sleepiness did not deteriorate.
This research investigated whether action semantic knowledge influences mental simulation during sentence comprehension. In Experiment 1, we confirmed that the words of face-related objects include the perceptual knowledge about the actions that bring the object to the face. In Experiment 2, we used an acceptability judgment task and a word-picture verification task to compare the perceptual information that is activated by the comprehension of sentences describing an action using face-related objects near the face (near-sentence) or far from the face (far-sentence). Results showed that participants took a longer time to judge the acceptability of the far-sentence than the near-sentence. Verification times were significantly faster when the actions in the pictures matched the action described in the sentences than when they were mismatched. These findings suggest that action semantic knowledge influences sentence processing, and that perceptual information corresponding to the content of the sentence is activated regardless of the action semantic knowledge at the end of the sentence processing.
This study investigated the development of “mindreading” in young adults. Forty university students were divided into two groups (role-play group and no-role-play group). Then they participated in a perspective-taking task in which the use of mindreading is essential. The participants viewed a computer display of eight familiar objects in different compartments of a wall divider with four rows of four compartments. Some of the compartments were open to see through, while others had back panels and thus which, if any, object was present could only be seen from the participant's side. They were instructed to touch the display corresponding to an object in a compartment in accord with the instructions of a “manager” who stood behind the divider and thus could not see into all of the compartments. The no-role-play group made more errors than the role-play group, and took longer to respond. The effects of role play lasted during five successive task blocks. These results suggest that experience with role play activates mindreading in this perspective-taking task.
Although social solidarity is an essential component that helps maintaining social order, what produces solidarity and how does it work have not been fully investigated. We conducted an experiment to examine whether experiencing different forms of social exchange produces different levels of solidarity. We compared four forms of social exchange: reciprocal exchange (exchange resources without negotiation), negotiated exchange (with negotiation), pure-generalized exchange (giver can choose who to give) and chain-generalized exchange (giver cannot choose who to give). Two dimensions classify these exchanges: the number of players (two vs. more than two), and involvement of negotiation. Reciprocal and negotiated exchanges occur within dyads, while pure- and chain-generalized exchanges involve three or more players. Only the negotiated exchange involves negotiation process; the other exchanges are purely unilateral giving. Participants played a one-shot social dilemma game (SDG) before and after social exchange session. The more the players cooperated in SDG, the stronger the social solidarity. Results show that the cooperation rate in SDG increased more in the reciprocal, pure- and chain-generalized exchange conditions than that in the negotiated exchange condition, suggesting that social solidarity is facilitated by experiencing social exchange which does not involve negotiation.
We propose a new method, called index K, to estimate the degree of differential item functioning (DIF) on a questionnaire or test taken by multiple groups. A computer program (EasyDIF) was developed to calculate index K. In developing the program, the three following concerns were paramount: (a) the program is applicable when there are more than three groups to be analyzed, (b) it is able to accommodate polytomous items, such as a Likert scale, and (c) details of DIF can be presented in a graph. In simulations and using Big Five scale data, the performance of index K was comparable to the Mantel-Haenszel method and to the Poly-SIBTEST. It is necessary to repeat the calculations to obtain index K. However, because EasyDIF has a graphical user interface, it was intuitively easy to use. Therefore, the results were easier to obtain using EasyDIF.
This study developed a Japanese version of the Child Social Preference Scale, which measures children's social withdrawal. In addition, we examined developmental changes of children's withdrawal and the relationships between withdrawal and problematic behaviors. The participants were 7 012 mothers of preschool, elementary school, and middle school children. A factor analysis revealed a two-factor solution of shyness and social disinterest, which is consistent with previous studies. Shyness decreased as children's grade level increased. Social disinterest changed in a quadratic manner. The shyness score was lowest in the lower grades of elementary school. Shyness was related to more emotional symptoms, more peer relationship problems, and less prosocial behavior. Social disinterest was related to peer relationship problems. The importance of the distinction between shyness and social disinterest is discussed.
This study analyzed the statistical power of research studies published in the “Japanese Journal of Psychology” in 2008 and 2009. Sample effect sizes and sample statistical powers were calculated for each statistical test and analyzed with respect to the analytical methods and the fields of the studies. The results show that in the fields like perception, cognition or learning, the effect sizes were relatively large, although the sample sizes were small. At the same time, because of the small sample sizes, some meaningful effects could not be detected. In the other fields, because of the large sample sizes, meaningless effects could be detected. This implies that researchers who could not get large enough effect sizes would use larger samples to obtain significant results.