Rats (Rattus norvegicus) find occupancy of a restraint tube rewarding

Two experiments evaluated whether rats' occupancy of a restraint tube is reinforcing. In Experiment 1, each rat in the 0-min group moved freely in a chamber where a wall blocked access to a restraint tube. After 10 min the wall was removed, permitting 15 min of chamber access and tube entry. The other 2 groups were locked in the tube for 10 and 20 min respectively before release into the chamber for 15 min. Across sessions, rats locked up for 10 and 20 min entered the tube more frequently than rats in the 0-min group, and during the first 2 sessions rats in the 20-min group stayed in the tube longer than the other groups. Over sessions this difference disappeared. However, for all groups and sessions the mean percentage of session time in the tube exceeded chance expectations. This result suggests tube occupation was reinforcing. In Experiment 2’s Phase 1, rats could enter an open tube. On exiting, the tube door closed. A lever press opened the door for the rest of the 1-hr session. In Phase 2, these rats were locked in the tube for 10 min before the door opened. Upon exiting, the door closed. As in Phase 1, a lever press opened the door for the rest of the session. The latency between pressing and tube entry decreased over sessions, indicating that tube entry reinforced lever pressing. These results are difficult to reconcile with accounts of rat empathy based on the thesis that tube restraint distresses occupants.     

Effects of the degree of fluctuation on subjective preference for a 1 Hz flickering light

Humans are believed to have a preferred amount of stimulus variation in their perceptual environment. Here, paired comparison tests were conducted to examine whether the fluctuation of a flickering light improves subjective preference. Sine-wave and bandpass noise acted as the light source. We have previously shown that the preferred temporal frequency of a flickering light without any fluctuation is approximately 1 Hz (Soeta et al 2002 Journal of the Optical Society of America A 19 289 - 294). This was used as the center frequency of the light source. The bandwidth was set at 1, 2, 4, 8, and 16 Hz, to control the amplitude of the first peak of the autocorrelation function, phi1. Results show that the preferred phi1 of a flickering light is 0.46.     

Mental Health Inventory for Infants: Scale Development and Japanese Infants’ Characteristics

Early detection and treatment promote positive outcomes in mental health problems among infants. This study developed a simple and reliable screening inventory for infants’ mental health. Participants were 579 primary caregivers who had Japanese infants aged 2–6 years. Participants evaluated their children using the Mental Health Inventory for Infants (MHII; developed in this study), which contains 24 items. Exploratory factorial analysis identified the MHII factor structure; confirmatory factorial analysis examined its factorial validity. Internal consistency and criterion-related validity were also examined. Irritability (8 items), somatic symptoms (6 items), and signs of insecurity (4 items) were identified as factors in the MHII; each of these factors measures a critical aspect of infants’ mental health. The MHII’s internal consistency and scale homogeneity were acceptable; its criterion-related validity was supported. In this study, male infants exhibited greater irritability and less insecurity than females. The present results support the MHII’s reliability and validity; additionally, they indicate that caregivers may use the MHII to quickly screen for three critical aspects of infants’ mental health. We expect that the MHII will be used for early detection of mental health difficulties in infants to facilitate treatment.     

Comparisons of Australians and Japanese on group-based cooperation

A cross-societal experiment with 49 Australian and 56 Japanese participants examined if the group heuristic account of ingroup-favoring behavior in a Prisoner's Dilemma game can be extended beyond the minimal group situation to a situation involving an enduring social category (i.e. participant's nationality). Participants played a Prisoner's Dilemma game five times, each time with a different partner. Two of the five partners were ingroup members, two were outgroup members, and the nationality of one partner was not known. Furthermore, one of the two ingroup (or outgroup) partners knew that the participant was a member of the same (or the other) nationality, and the other did not know it. The results indicated that the knowledge that the partner had about the nationality of the participant exerted an effect only when the partner was an ingroup member. No major difference was found between Australian and Japanese participants. An outgroup-favoring cooperation pattern was observed, but that pattern was shown to be a result of fairness concerns among Australian participants and of positive stereotypes of Australians among Japanese participants.     

Neuroscientific information bias in metacomprehension: The effect of brain images on metacomprehension judgment of neuroscience research

In the present study, we investigated how brain images affect metacomprehension judgments of neuroscience research. Participants made a prereading judgment of comprehension of the text topic and then read a text about neuroimaging findings. In Experiment 1, participants read text only or text accompanying brain images. In Experiment 2, participants read text accompanying bar graphs or text accompanying brain images. Then participants were asked to rate their comprehension of the text. Finally, they completed comprehension tests. The results of Experiment 1 showed that the text accompanying brain images was associated with higher metacomprehension judgments than was the text only, whereas the performance of the comprehension test did not differ between each condition. The results of Experiment 2 showed that the text accompanying brain images was associated not only with credibility of the text, but also with higher metacomprehension judgments than was the text accompanying the bar graphs, whereas the performance of the comprehension test did not differ between each condition. The findings suggest that the readers’ subjective judgments differ from actual comprehension.     

Thinking about “why” eliminates retrieval‐induced forgetting: Levels of construal affect retrieval dynamics

The present study examined how levels of construal affect retrieval‐induced forgetting. Higher‐level construal is associated with the focus on the similarities among stimuli, suggesting that high‐level construal promotes relational processing. Based on this fact, retrieval‐induced forgetting may be reduced or eliminated under high‐level construal condition because of the effect of relational processing. Two experiments were conducted using a retrieval‐practice paradigm with different stimuli while priming the level of construal. A meta‐analysis synthesizing the results showed that retrieval‐induced forgetting occurred under the low‐level construal condition, whereas forgetting did not occur under the high‐level construal condition. These results suggest that abstract thinking can eliminate retrieval‐induced forgetting because of relational processing, demonstrating the role of the levels of construal on memory inhibition.     

Does a rat free a trapped rat due to empathy or for sociality?

This report evaluates whether a rat releasing a trapped rat from a restraint tube is better explained as due to its empathic motivation or to the pursuit of social contact. In the first condition, each of six rats chose in an E maze between entering an empty goal box versus entering a goal box where its entrance caused a rat trapped in a restraint tube to be released. Rats preferred the goal box with the trapped rat over the empty goal box. In the second condition, these rats chose between releasing a restraint‐tube‐trapped rat in one goal box and another rat in the second goal box that was not locked into its restraint tube. Rats showed no preference between alternatives. In the third condition, rats chose between a goal box containing a rat with an open restraint tube and an empty goal box. Rats preferred the rat with the open restraint tube over the empty goal box. These results support attributing the response of releasing a rat from a restraint tube to the reinforcing power of social contact rather than interpreting this response as empathically motivated.     

Humans (Homo sapiens) fail to show an inequity effect in an “up-linkage” analog of the monkey inequity test

Brosnan and de Waal (Nature 425:297–299, 2003) claimed that if a capuchin sees another capuchin receiving a superior food, she tends to reject an inferior, previously acceptable food. They related this phenomenon to human inequity aversion. This phyletic extension is “down linkage,” because nonhuman research is interpreted in terms of human research. The present experiment makes an “up-linkage” test of this claimed connection by attempting to reproduce the capuchin-inequity effect in humans. In Experiment 1’s equity condition, a subject and an adjacent confederate each clicked a computer mouse to mark the number “7” from a random numbers table, earning 0.5 yen per mark. In the inequity condition, the confederate’s pay rate was twice that of the subject. There was no between-condition difference in quitting times or likelihoods. Experiment 2 replicated Experiment 1 except, before beginning, the subject and confederate clicked a mouse over a rapidly switching message that said they would earn either 0.5 or 1 yen per marked seven. For the equity condition in this rigged test, subject and confederate stopped the message at 0.5 yen, while in the inequity condition, these values were 0.5 and 1 yen, respectively. Now, inequity-condition subjects quit sooner than equity-condition subjects. Experiment 1 found no inequity effect, but Experiment 2 did. These results show that: (a) a sense of control/responsibility may be critical to an inequity effect and (b) the inequity effect putatively present in capuchins cannot be reproduced in an up-linkage human analog of that research, thereby calling this linkage into question. This report exemplifies that up- and down-linkage tests are often requisite to establish commonality of psychological process between nonhuman primates and humans.     

A RUNS‐TEST ALGORITHM: CONTINGENT REINFORCEMENT AND RESPONSE RUN STRUCTURES

Four rats' choices between two levers were differentially reinforced using a runs‐test algorithm. On each trial, a runs‐test score was calculated based on the last 20 choices. In Experiment 1, the onset of stimulus lights cued when the runs score was smaller than criterion. Following cuing, the correct choice was occasionally reinforced with food, and the incorrect choice resulted in a blackout. Results indicated that this contingency reduced sequential dependencies among successive choice responses. With one exception, subjects' choice rule was well described as biased coin flipping. In Experiment 2, cuing was removed and the reinforcement criterion was changed to a percentile score based on the last 20 reinforced responses. The results replicated those of Experiment 1 in successfully eliminating first‐order dependencies in all subjects. For 2 subjects, choice allocation was approximately consistent with nonbiased coin flipping. These results suggest that sequential dependencies may be a function of reinforcement contingency.