Left-side dominance for song discrimination in Bengalese finches (Lonchura striata var. domestica)

Male Bengalese finches are left-side dominant for the motor control of song in the sensorimotor nucleus (the high vocal center, or HVc) of the telencephalon. We examined whether perceptual discrimination of songs might also be lateralized in this species. Twelve male Bengalese finches were trained by operant conditioning to discriminate between a Bengalese finch song and a zebra finch song. Before training, the left HVc was lesioned in four birds and the right HVc was lesioned in four other birds. The remaining four birds were used as controls without surgery. Birds with a left HVc lesion required significantly more time to learn to discriminate between the two songs than did birds with a right HVc lesion or intact control birds. These results suggest that the left HVc is not only dominant for the motor control of song, but also for the perceptual discrimination of song. Accepted after revision: 11 September 2001 Electronic Publication     

Factors shaping vividness of memory episodes: visitors' long-term memories of the 1970 Japan World Exposition

This study investigated how visitors' psychological and behavioural factors, identified in the literature, shaped their vivid long-term memories of their experiences of the Japan World Exposition, Osaka, 1970 (Expo '70) as a context. In this study, 112 memory episodes were identified from the long-term memories of 48 participants; they were rated in terms of their memory vividness and on a set of factors including affect, agenda fulfilment, intentionality, and rehearsal. The influence of these factors on the vividness of episodic and/or autobiographic memories of experiences that occurred 34 years ago was examined in two stages. First, the relationship between memory vividness and individual factors was investigated separately. Second, the relationship between memory vividness and all factors was examined through a multiple regression analysis, and the relative importance of these factors on memory vividness identified. Stage one analysis showed that all factors except intentionality were related to memory vividness in individual analyses, and curvilinear relationships between memory vividness and the factors found. Stage two analysis, in which all factors were included in a multiple regression analysis, found that rehearsal was positively related to memory vividness and all other factors not significant in the presence of rehearsal.     

Dopamine D1 receptors regulate protein synthesis-dependent long-term recognition memory via extracellular signal-regulated kinase 1/2 in the prefrontal cortex

Several lines of evidence suggest that extracellular signal-regulated kinase1/2 (ERK1/2) and dopaminergic system is involved in learning and memory. However, it remains to be determined if the dopaminergic system and ERK1/2 pathway contribute to cognitive function in the prefrontal cortex (PFC). The amount of phosphorylated ERK1/2 was increased in the PFC immediately after exposure to novel objects in the training session of the novel object recognition test. An inhibitor of ERK kinase impaired long-term recognition memory 24 h after the training although short-term memory tested 1 h after the training was not affected by the treatment. The dopamine D1 receptor agonist increased ERK1/2 phosphorylation in the PFC in vivo as well as in cortical neurons in vitro. Microinjection of the dopamine D1 receptor antagonist into the PFC impaired long-term recognition memory whereas the D2 receptor antagonist had no effect. Immunohistochemistry revealed that exposure to novel objects resulted in an increase in c-Fos expression in the PFC. Microinjection of the protein synthesis inhibitor anisomycin into the PFC impaired the long-term recognition memory. These results suggest that the activation of ERK1/2 following the stimulation of dopamine D1 receptors is necessary for the protein synthesis-dependent long-term retention of recognition memory in the PFC.     

Effect of spatial position on visual search for 3-D objects

We examined whether the position of objects in external space affects the visual-search task associated with the tilt of 3-D objects. An array of cube-like objects was stereoscopically displayed at a distance of 4.5 m on a large screen 1.5 m above or below eye height. Subjects were required to detect a downward-tilted target among upward-tilted distractors or an upward-tilted target among downward-tilted distractors. When the stimuli consisted of shaded parallelepipeds whose upper/bottom faces were lighter than their side faces, the upward-tilted target was detected faster. This result was in accordance with the 'top-view assumption' reported in previous research. Displaying stimuli in the upper position degraded overall performance. However, when the shaded objects whose upper/bottom faces were darker than their side faces were displayed, the detection of a downward-tilted target became as efficient as that of an upward-tilted target only at the upper position. These results indicate that it is possible for the spatial position of the stimulus to promote the detection of a downward-tilted target when shading and perspective information are consistent with the viewing direction.     

Perceived group identity of outgroup members and anticipated rejection: People think that strongly identified group members reject non‐group members

Many studies of intergroup relations have examined the effects of group identity on various types of intergroup cognition and behavior. However, few studies have focused on the perceived group identity of outgroup members. This study examined the effects of perceptions of outgroup identity on anticipated rejection by an outgroup. In Study 1, we administered a questionnaire pertaining to 30 social groups to Japanese undergraduate and vocational students. The collective images and intra‐individual processes relating to perceived outgroup identity were investigated by applying correlation analysis and multilevel structural equation modeling. In Study 2, we conducted an experiment in which we manipulated the participants' perceptions of relative levels of outgroup members' identity. Both studies demonstrated, as predicted, that people anticipated rejection by strongly identified outgroup members more than by weakly identified outgroup members. Furthermore, in Study 2, anticipated same‐group favoritism mediated the relationship between the manipulation of perceived outgroup identity and anticipated rejection. These findings suggest the important role of perceived outgroup identity in intergroup cognition.     

Effects of cementite morphology on short-fatigue-crack propagation in binary Fe–C steel

The effects of cementite morphology on short-fatigue-crack propagation were investigated by subjecting smooth steel specimens to rotating-bending fatigue tests. Intergranular and transgranular cementite precipitation steels free of other phases were prepared through heat treatments. In the intergranular cementite precipitation steel, short-fatigue-crack propagation was decelerated at the grain boundaries, and accelerated in the grain interiors. In contrast, the transgranular precipitation steel showed the deceleration of the crack propagation in the grain interiors but not in the vicinity of the grain boundaries.     

The effects of linearity on sentence comprehension in oral and silent reading

This study examined the effects of linearity of language (e.g., de Saussure, 1916/1972) on performance on a sentence comprehension task, manipulating (a) presentation method (simultaneous, phrase, or flow) and (b) reading method (oral or silent reading). The study also examined the predictive powers of the digit span test (DST) and the reading span test (RST) for task performance. Fifty‐four undergraduate and graduate students participated in the experiment. The results showed that the DST score predicted performance on both garden‐path (GP) and non‐garden‐path (NGP) sentences, whereas the RST score did so only for GP sentences. This suggests that the sentence comprehension task requires not only comprehension but also temporarily storing verbal information, and that the RST score reflects the degree of tolerance for deviation from linearity. The results also revealed that silent reading has an advantage over oral reading in simultaneous presentation and vice versa in flow presentation, whereas the difference between reading methods disappeared in phrase presentation. This suggests that oral and silent reading require different strategies to facilitate sentence comprehension.     

Temperature dependence of the stacking fault energy of glide set-dissociated dislocations in Si

Recently, it was found that the dissociation distance of glide set dislocations introduced in Si just below the melting temperature by laser shock peening (LSP) is unusually wide (Iwata et al. J. Jpn Inst. Met. Materi.,79(2015),308–314). In order to distinguish whether or not this is to be attributed to uncorrelated motions of leading and trailing Shockley partials or the intrinsic temperature dependence of the stacking fault energy (SFE), dislocations introduced by LSP were annealed at 1350 °C, which should be high enough for the uncorrelated partials to assume the equilibrium correlated configuration. It was found that this unusual widening of a dissociated dislocation introduced by LSP is attributed to uncorrelated motions of Shockley partials. Following this conclusion, the temperature dependence of the intrinsic SFE of Si was determined on correlated dissociated dislocations up to near the melting temperature. The intrinsic SFE of Si shows only negligibly small temperature dependence from 400 °C up to near the melting temperature.     

Evidence for Mixed Processes in Normal/Mirror Discrimination of Rotated Letters: A Bayesian Model Comparison Between Single- and Mixed-Distribution Models1

When determining whether a rotated letter is normal or mirrored, an observer mentally rotates the letter to its canonical orientation. To account for patterns of response times (RTs) for the normal/mirror discrimination of rotated letters, previous research formulated a model that postulated a mixture of trials with and without mental rotation. While this model could explain the curvilinear relationship that has been found between averaged RT and letter orientations, the curved RT function is still open to alternative explanations without assuming mixed processes. To address this issue and test the mixed-process hypothesis more directly, we analyzed trial-by-trial RT data instead of averaged RTs by employing a Bayesian model comparison technique. If rotation and non-rotation trials are mixed, trial-by-trial RTs for letters in a particular orientation should not follow a single distribution but a mixed one formed from the superposition of two separate distributions, one for rotation and one for non-rotation trials. In the present study, we compared single- and mixed-distribution models. Bayes-factor analysis showed decisive support for the mixed-distribution model over the single-distribution model. In addition, using the widely applicable information criterion (WAIC), the predictive accuracy of the mixed-distribution model was found to be as high as that of the single-distribution model. These results indicated the involvement of mixed processes in normal/mirror discrimination of rotated letters. The usefulness of statistical modeling in psychological study and necessary precautions to take in the interpretation of the parameters of unconfirmed models are also discussed.     

Cortical shape adaptation transforms a circle into a hexagon: a novel afterimage illusion

After viewing a colored figure on a uniform gray background, an observer will see a negative afterimage after the colored figure disappears. This study shows that the shapes of afterimages vary systematically according to the shape of the adaptation stimuli, a phenomenon that could be caused only by cortical shape adaptation. In the experiments reported here, participants typically saw a hexagonal afterimage after viewing a circle and sometimes saw a circular afterimage after viewing a hexagon. When observers were adapted to rotating circles or hexagons, which produced the same circular retinal painting, they reliably reported that afterimages of circles appeared as hexagons, and vice versa. Furthermore, the fact that this effect also arose through interocular transfer confirms that a cortical process with binocular inputs must have contributed to it. This novel finding reveals that afterimage formation is determined mainly by a cortical process, not by retinal bleaching, and that rival mechanisms detect corners and curves of shapes in cortical processing.