The present study investigated the relation between schizotypy and motor control against self- or other-produced action. We used an unloading task to focus on the timing component of anticipatory motor control. In the task, a weight was removed from a participants' hand by the participants themselves or by an experimenter (voluntary versus imposed unloading). Postural disturbance at the removal timing was measured as an index of predictive function in motor control. We hypothesized that the postural disturbance in the voluntary unloading would be positively related to schizotypal traits; however, the results did not support this theory. The results showed almost zero correlation between the schizotypy scores and the postural disturbance in the voluntary unloading condition. In contrast, the schizotypy scores positively correlated with the postural disturbance in the imposed unloading condition. These findings were replicated across two participant groups and two schizotypy scales. Further analyses on subscales of the schizotypy questionnaire found moderate levels of positive correlation between each subscale for Cognitive-Perceptual and Disorganization factors and the disturbance. Accordingly, the present study did not support the idea that non-pathological individuals with high schizotypal traits have deficits in prediction of self-produced actions, at least for a temporal domain. Instead, the results suggested that individuals with high schizotypal traits, particularly for the positive and disorganization symptoms, are not good at responding to others-produced actions. The schizophrenic symptoms were discussed in terms of the failure in the processes executed after calculating prediction of sensory consequences and dysfunction in internal models for "other people".

According to agency memory theory, individuals decide whether "I did it" based on a memory trace of "I am doing it". The purpose of this study was to validate the agency memory theory. To this end, several hand actions were individually presented as samples, and participants were asked to perform the sample action, observe the performance of that action by another person, or imagine performing the action. Online feedback received by the participants during the action was manipulated among the different conditions, and output monitoring, in which participants were asked whether they had performed each hand action, was conducted. The rate at which respondents thought that they themselves had performed the action was higher when visual feedback was unaltered than when it was altered (Experiment 1A), and this tendency was observed across all types of altered feedback (Experiment 1B). The observation of an action performed by the hand of another person did not increase the rate at which respondents thought that they themselves had performed the action unless the participants actually did perform the action (Experiments 2A and 2B). In Experiment 3, a relationship was observed between the subjective feeling that "I am the one who is causing an action" and the memory that "I did perform the action". These experiments support the hypothesis that qualitative information and sense of "self" are tagged in a memory trace and that such tags can be used as cues for judgements when the memory is related to the "self".

Using functional MRI, we investigated reality monitoring for auditory information. During scanning, healthy young adults heard words in another person's voice and imagined hearing other words in that same voice. Later, outside the scanner, participants judged words as "heard," "imagined," or "new." An area of left middle frontal gyrus (Brodmann's area, or BA, 6) was more active at encoding for imagined items subsequently correctly called "imagined" than for items incorrectly called "heard." An area of left inferior frontal gyrus (BA 45, 44) was more active at encoding for items subsequently called "heard" than "imagined," regardless of the actual source of the item. Scores on an Auditory Hallucination Experience Scale were positively related to activity in superior temporal gyrus (BA 22) for imagined words incorrectly called "heard." We suggest that activity in these areas reflects cognitive operations information (middle frontal gyrus) and semantic and perceptual detail (inferior frontal gyrus and superior temporal gyrus, respectively) used to make reality-monitoring attributions.

Prior research has suggested that configural resemblance between a current scene and a previously experienced but forgotten one may trigger deja vu experiences. The present study examined whether there is a relationship between the frequency of actual deje vu experiences, measured by questionnaires, and sensitivity to a configural resemblance between past and present events, measured by questionnaires, and between two scenes presented simultaneously in the laboratory. We measured familiarity ratings and remember-know judgements of several scenes. Some scenes had been previously presented, some were similar to previously presented scenes and the others were dissimilar. Deja vu tendencies were significantly correlated with sensitivity to similarity in the measured questionnaires and in the laboratory, as well as to a feeling of familiarity for similar scenes. In this study, we found for the first time that people who more frequently experience deje vu states were also more likely to regard themselves as sensitive to similarity and more likely to notice the similarity between two scenes in the laboratory.

Previous studies have shown that contextually high-predictability ideas are essential for one to sense the authorship of thoughts and that having the sense that one came up with an idea of one's own, instead of through hearing of another's idea, results in the feeling that one has output the ideas. In this study, we investigated the effects of an idea's predictability on the misattribution of another's thought to oneself. The participants were asked to write down two original ideas about how to use various objects while avoiding the duplication of another's ideas that had been presented beforehand in an input-output phase. In the monitoring phase (1 week and 1 month after the input-output phase), the participants were asked whether each idea had been generated by them, by another, or not generated at all. We found that a high-predictability idea is likely to be regarded with the notion "I generated the idea." This tendency increased with time, suggesting that participants were more likely to have a sense of authorship when high-predictability ideas were presented. We also discovered that they were more likely to conclude that the source of high-predictability ideas was the "Self." We discussed the results from the viewpoint of the participant's sense of agency as well.

We investigated output-monitoring errors over speech based on findings in the research on the sense of agency. Several words were presented one-by-one, and we asked participants to say the word aloud, mouth the word, or imagine saying the word aloud. Later, participants were asked whether each word was said aloud. We found that the "said aloud" response was higher for generated words than that for observed words; it was decreased when the pitch of the feedback was lowered but still higher than when no feedback was received, and it was the same when no feedback was received and when feedback was replaced by another's voice. Furthermore, we found that the "said aloud" response did not decrease even when the altered feedback was received with a short delay. These results were discussed according to the sense of agency and agency memory.

Previous studies have suggested that a tendency to externalize internal thought is related to auditory hallucinations or even proneness to auditory hallucinations (AHp) in the general population. However, although auditory hallucinations are related to emotional phenomena, few studies have investigated the effect of emotional valence on the aforementioned relationship. In addition, we do not know what component of psychotic phenomena relate to externalizing bias. The current study replicated our previous research, which suggested that individual differences in auditory hallucination-like experiences are strongly correlated with the external misattribution of internal thoughts, conceptualized in terms of false memory, using the Deese-Roediger-McDermott (DRM) paradigm. We found a significant relationship between experimental performance and total scores on the Launay-Slade Hallucination Scale (LSHS). Among the LSHS factors, only vivid mental image, which is said to be a predictor of auditory hallucinations, was significantly related to experimental performance. We then investigated the potential effect of emotional valence using the DRM paradigm. The results indicate that participants with low scores on the LSHS (the low-AHp group in the current study) showed an increased discriminability index (d') for positive words and a decreased d' for negative words. However, no effects of emotional valence were found for participants with high LSHS scores (high-AHp group). This study indicated that external misattribution of internal thoughts predicts AHp, and that the high-AHp group showed a smaller emotional valence effect in the DRM paradigm compared with the low-AHp group. We discuss this outcome from the perspective of the dual-process activation-monitoring framework in the DRM paradigm in regard to emotion-driven automatic thought in false memory.

We can share various feelings with others just through observation, as if it were an automatic resonance. This connective function between the self and others could promote the facilitation of our social communication; however, it is still unclear as to how it works in terms of self-other representation. In this study, we showed participants a picture of a model holding a ball, which was weighted with sand. We instructed participants to move one of their arms to a horizontal position and hold it immobile. Those participants who knew the actual weight of the ball (1 kg) tended to raise this arm above the horizontal, in response to their expectation of the need to resist the weight of the ball. This compensatory reaction to the illusion of heaviness suggests that our bodily resonance could be mandatory and predictive. We discuss this new behavioral phenomenon in terms of motor simulation or the mirror-neuron system.

When participants observed a rubber hand being touched, their sense of touch was activated (rubber hand illusion: RHI). While this illusion might be caused by multi-modal integration, it may also be related to empathic function, which enables us to simulate the observed information. We examined individual differences in the RHI, including empathic and schizotypal personality traits, as previous research had suggested that schizophrenic patients would be more subject to the RHI. The results indicated that people who experience a stronger RHI might have stronger empathic and schizotypal personalites simultaneously. We discussed these relationships in terms of self-other representations.

The present study examined the relationship between the atypical cerebral lateralization pattern represented in hand and foot preferences and schizotypal personality traits, especially proneness to auditory hallucinations as related to a sense of agency. A sense of agency, measured with questionnaires in the present study, is the sense that "I am the one who causes the actions." Although atypical lateralization and an abnormal sense of agency may be related to schizophrenia or schizotypal personality, the connection between them has remained unclear. The present study used cluster analysis to categorize the handedness-footedness combinations. The results indicated that people with right-handedness and left-footedness may have more schizotypal traits and that their abnormal sense of agency may cause schizotypal personality traits. Although the reasons for crossed lateral preference remain unclear, we discuss this in terms of early switching in handedness, which may underlie atypical lateralization and lead to the experience of auditory hallucinations deriving from an abnormal sense of agency.

Previous studies have suggested that auditory hallucination is closely related to thought insertion. In this study, we investigated the relationship between the external misattribution of thought and auditory hallucination-like experiences. We used the AHES-17, which measures auditory hallucination-like experiences in normal, healthy people, and the Deese-Roediger-McDermott paradigm, in which false alarms of critical lure are regarded as spontaneous external misattribution of thought. We found that critical lures elicited increased the number of false alarms as AHES-17 scores increased and that scores of AHES-17 predicted the rate of false memory of critical lures. Furthermore, we revealed that the relationship between AHES-17 scores and the rates of false alarms to critical lures was strictly linear. Therefore, it might be said that individual differences in auditory hallucination-like experiences are highly related to the external misattribution of thought. We discussed these results from the perspective of the sense of agency over thought.

Our purpose was to investigate the relationships between the names of items that easily evoke nostalgic feelings and nostalgic advertisements from the perspective of nostalgia for the names of these items and from the perspective of source monitoring. We measured the effect of nostalgia on source monitoring and whether the names of items evoked nostalgic feelings when they were presented alone. We found that, from the perspective of the nostalgic feelings, we directly demonstrated that the names of articles that easily evoke nostalgic feelings are more likely to evoke nostalgia when they are presented with nostalgic advertisements than when they are presented with non-nostalgic advertisements. From the perspective of source monitoring, we revealed that nostalgic advertisements are more forgettable than non-nostalgic advertisements when they present the names of articles that easily evoke nostalgic feelings.

Schizotypal personality traits (schizotypy) might be seen as on a continuum with schizophrenia. However, controversy remains with regard to whether this continuum is quasi-dimensional, applying only to people with schizophrenia and schizotypy, or fully dimensional, applying to all people. If the fully dimensional model is accurate, schizotypy could be described by the same personality theories as are applied to people in general. We examined the relationship between schizotypy and the five-factor model of personality (FFM), which is arguably the most established contemporary personality theory. When we assumed a hierarchic structure of schizotypy factors, we found that the FFM scales could explain schizotypy fairly well regardless of the questionnaires used, suggesting that schizotypy might represent a variation better understood by reference to typical dimensions of personality, though it might still indicate a predisposition to schizophrenia. This article discusses this conclusion in relation to each of the five personality factors. A perspective that situates schizophrenia on a continuum with general personality variations implies that this disorder constitutes a potential risk for everyone and, thus, helps to promote understanding and correct misunderstandings that contribute to prejudice.

This study investigated the effects of imagining speaking aloud, sensorimotor feedback, and auditory feedback on respondents' reports of having spoken aloud and examined the relationship between responses to "spoken aloud" in the reality-monitoring task and the sense of agency over speech. After speaking aloud, lip-synching, or imagining speaking, participants were asked whether each word had actually been spoken. The number of endorsements of "spoken aloud" was higher for words spoken aloud than for those lip-synched and higher for words lip-synched than for those imagined as having been spoken aloud. When participants were prevented by white noise from receiving auditory feedback, the discriminability of words spoken aloud decreased, and when auditory feedback was altered, reports of having spoken aloud decreased even though participants had actually done so. It was also found that those who have had auditory hallucination-like experiences were less able than were those without such experiences to discriminate the words spoken aloud, suggesting that endorsements of having "spoken aloud" in the reality-monitoring task reflected a sense of agency over speech. These results were explained in terms of the source-monitoring framework, and we proposed a revised forward model of speech in order to investigate auditory hallucinations.

Our purpose in this study was to investigate the effects of cognitive operations and perceptual details on speech source monitoring. In Phase 1, correctly spelled words and anagrams were presented in Expt 1. Words were read aloud by participants, by a same-sex voice, or by an opposite-sex voice. Immediately after Phase 1, in Phase 2, participants were asked whether each word had been read aloud by the participants themselves, by a same-sex voice, or by an opposite-sex voice. Source discrimination between own speech and that produced by a same-sex voice was poorer than between own speech and an opposite-sex voice. In addition, misattribution of the speech of another to one's self increased as the level of cognitive effort required for the task increased. In Expt 2, misattributions to same-sex voice were assigned 'know' responses more frequently and misattributions to one's self were assigned 'remember' responses more frequently. These results suggest that qualitative characteristics such as perceptual detail and cognitive operations are differentially influencing misattributions to the self and those to same-sex voices.

Previous studies have suggested that the left and right hands have different specialties for motor control that can be represented as two agents in the brain. This study examined how coordinated movements are performed during bimanual reaching tasks to highlight differences in the characteristics of the hands. We examined motor movement accuracy, reaction time, and movement time in right-handed subjects performing a three-dimensional motor control task (visually guided reaching). In the no-visual-feedback condition, right-hand movement had lower accuracy and a shorter reaction time than did left-hand movement, whereas bimanual movement had the longest reaction time, but the best accuracy. This suggests that the two hands have different internal models and specialties: closed-loop control for the right hand and open-loop control for the left hand. Consequently, during bimanual movements, both models might be used, creating better control and planning (or prediction), but requiring more computation time compared to the use of one hand only.

We investigated the relationship between levels of delusional ideation (whether positive or negative delusions) and the activation and distortion of memory by using pairs of positive and negative adjectives describing personality traits where those adjectives had similar meanings. We presented one of each pair of adjectives in the learning phase. Immediately after the learning phase in Experiment 1, we asked whether each adjective had been presented. Participants with high (positive or negative) delusional ideation were more likely to indicate that they had learned adjectives that they had not actually learned. This finding suggested that non-learned positive (or negative) adjectives that were associated with learned negative (or positive) adjectives were more likely to be activated in participants prone to positive (or negative) delusional ideation. However, in Experiment 2, two forced-choice tests were conducted immediately after the learning phase. In this context, participants, regardless of their proneness to delusional ideation, could almost always correctly distinguish what had and had not been presented, suggesting that the activation of learned items was still stronger than that for non-learned items in the immediate test. As time passed, the proportion of false alarms for positive or negative adjectives was higher in the two forced-choice tests among those with high proneness to (positive or negative) delusional ideation, suggesting that participants with delusional ideation were increasingly likely to depend on internal conditions for retrieval over time. Nous avons examiné la relation entre les niveaux d'idéation illusoire (qu'elle soit positive ou négative) et l'activation et la distorsion de la mémoire, en utilisant des paires d'adjectifs positifs et négatifs à significations similaires décrivant des traits de personnalité. Nous avons présenté un membre de chaque paire d'adjectifs lors d'une phase d'apprentissage. Dans une première expérience, immédiatement après la phase d'apprentissage, nous avons demandé si chaque adjectif avait été présenté. Les participants ayant un niveau d'idéation illusoire (positive ou négative) élevé étaient plus susceptibles d'indiquer qu'ils avaient appris les adjectifs qu'ils n'avaient pas appris. Ce résultat suggérait que les adjectifs positifs (ou négatifs) non appris qui étaient associés à des adjectifs négatifs (ou positifs) appris étaient plus susceptibles d'être activés chez les participants portés à l'idéation illusoire positive (ou négative). Dans une deuxième expérience, deux tests à choix forcés ont été menés immédiatement après la phase d'apprentissage. Dans ce contexte, les participants, indépendamment de leur tendance à l'idéation illusoire, pouvaient presque toujours distinguer correctement ce qui avait été présenté de ce qui n'avait pas été présenté, suggérant que l'activation des items appris était encore plus forte que celle des items non appris dans le test immédiat. Avec le temps, la proportion de fausses alarmes pour les adjectifs positifs ou négatifs était plus élevée dans les deux tests à choix forcés chez les participants portés à l'idéation illusoire (positive ou négative), ce qui suggère que les participants avec idéation illusoire étaient de plus en plus susceptibles de dépendre de leurs conditions internes lors du rappel à mesure que le temps passait. En este estudio se investigó la relación entre los niveles de ideación delusional (tanto delusiones positivas como negativas) y la activación y distorsión de la memoria a través del uso de pares de adjetivos positivos y negativos que describen rasgos de personalidad. Estos pares de adjetivos tenían significados similares. En la fase de aprendizaje se presentó un miembro de cada par de adjetivos. Inmediatamente después de la fase de aprendizaje se realizó el primer experimento, en el cual se preguntó al participanten si es que se le habían presentado cada uno de los adjetivos. Los participantes con elevada ideación delusiva (positiva o negativa) reportaran con una mayor probabilidad haber aprendido adjetivos que en realidad no se les había presentado. Este hallazgo sugiere que adjetivos positivos (o negativos) no aprendidos que estaban asociados con adjetivos negativos (o positivos) aprendidos, tenían una mayor probabilidad de ser activados en participantes propensos a una ideación delusiva positiva (o negativa). En el segundo experimento se llevaron a cabo inmediatamente después de la fase de aprendizaje dos pruebas de decisión forzada. En este contexto se pudo observar que los participantes a pesar de su tendencia hacia una ideación delusional, lograron distinguir en la mayoría de los casos correctamente entre los adjetivos que les fueron presentado y lo que no. Esto sugiere que la activación de los items aprendidos fue mucho más intensa que la de los items no aprendidos en el test. Sin embargo se pudo observar en los participantes de las dos pruebas de decisión forzada que con el paso del tiempo el porcentaje de falso reconocimiento de adjetivos positivos y negativos fue más elevado entre aquellas personas con una alta tendencia hacia una ideación delusional (positiva o negativa). Esto sugiere que en participantes con ideación delusional el reconocimiento de información a lo largo del tiempo probablemente es muy dependiente de condiciones internas.

Auditory hallucinations are important symptoms when making a diagnosis of schizophrenia. Since normal people may also experience auditory hallucinations, there may be a spectrum of auditory hallucinations ranging from those experienced in schizophrenia to those experienced by normal people. To assess the propensity to auditory hallucinations in a non-clinical population, we selected forty items from the questionnaire in Tanno, Ishigaki, & Morimoto (1998) and developed the Auditory Hallucination-like Experience Scale (AHES). Test-retest reliability showed that the AHES was internally consistent. There were high correlations between the AHES and the STA subscale and the overall O-LIFE (especially'unusual experiences'), both of which are thought to be strongly related to schizophrenia. Furthermore, the rate of false positives was higher in people more prone to auditory hallucinations than in the group less prone to auditory hallucinations. Factor analysis revealed that the AHES consists of four factors. The results suggest that the AHES has high reliability and validity as a measure of susceptibility to hallucinations.

A "sense of agency" involves a contemporaneous experience that the "self" causes the actions performed by the "self" (i.e., "I am the one who causes my actions"). This may comprise the main component of self-consciousness. The present research focuses on the development of a questionnaire to investigate the subjective aspects of a sense of agency. We selected items from the extant relevant measures and from previous empirical studies, and conducted four longitudinal surveys with additional scales. Statistical computations confirmed the validity and reliability of the Sense of Agency Scale (SOAS), consisting of seventeen items involving three factors. Furthermore, the results indicated that these three factors might be organized hierarchically, with each factor showing a unique relationship with emotional or social traits. This novel finding, emerging from the Sense of Agency Scale, would have been difficult to obtain via traditional empirical studies.

Atypical cerebral lateralization in motor and language functions in regard to schizotypal personality traits in healthy populations, as well as among schizophrenic patients, has attracted attention because these traits may represent a risk factor for schizophrenia. Although the relationship between handedness and schizotypal personality has been widely examined, few studies have adopted an experimental approach. This study consisted of three experiments focusing on motor and language functional lateralization in regard to schizotypal personality in the absence of mental illness: line-drawing, finger tapping, and a semantic go/no-go task. The results suggested that positive schizotypal personality might be related to functional non-lateralization in regard to at least some functions (e.g., spatial motor control and semantic processing in the present study). Subjects with high schizotypal personality traits performed equally with their right and left-hands in the line-drawing task and they reacted equally with their right and left-hands in a semantic go/no-go task involving semantic auditory stimuli presented in both ears. However, those low in schizotypal personality traits showed typical lateralization in response to these tasks. We discuss the implications of these findings for schizotypal atypical lateralization.

We investigated how limiting attentional resources during a prospective memory task influences old and new judgement and output monitoring, using a paradigm designed by Marsh and Hicks (1998) and multinomial processing models. Our study revealed two novel findings. First, when participants do not remember whether an item was presented and whether they performed the prospective memory task, the risk of a participant guessing that he/she had successfully performed the prospective memory task was greater when more attentional resources were available. Second, even when a participant had successfully performed the prospective memory task, he/she remembered that the item had been actually presented less when the available attentional resources were limited.

BACKGROUND: Positive schizophrenic symptoms, especially passivity phenomena, including auditory hallucinations, may be caused by an abnormal sense of agency, which people with schizotypal personality traits also tend to exhibit. A sense of agency asserts that it is oneself who is causing or generating an action. It is possible that this abnormal sense of self-agency is attributable to the abnormal prediction of one's own movements in motor control. METHOD: We conducted an experiment using the "disappeared cursor" paradigm in which non-clinical, healthy participants were required to click on a target using an invisible mouse cursor. Prediction error was defined as the distance between the target and the click point. RESULTS: The results showed that schizotypal personality traits, but not depressive or anxious traits, were correlated with deficits in predicting movements of the subjects' left hand. In particular, auditory hallucination proneness had the strongest relationship with movement prediction error. In this report, we also discuss the error tendency (overestimations or underestimations of one's own movements). CONCLUSIONS: This finding is in accordance with the idea that passivity phenomena or proneness may be caused by the abnormal prediction of one's own actions or movements.

We used two experiments to investigate factors related to error in output monitoring. In the learning phase, participants were presented with several action phrases from either an internal source (imagine) or an external source (enact). In the recall test phase, participants were asked to recollect as many action phrases as possible. In the output monitoring test phase, participants were asked to judge whether they had recalled each item during the recall test phase. The first and second experiments differed only in the type of recollection participants used (enact vs. imagine). We found that repeated enacting during the learning phase increased output monitoring error under conditions where participants counted numerals as a secondary task during the recall test phase (experiments 1A, 2A) and under conditions where the output monitoring test phase was conducted seven days after the recall test phase (experiments 1B, 2B). These results reveal that when participants were unable to use conscious recollection during the recall test phase, they did not rely on source memory but only relied on the strength of the memory.

The interaction of cue-word specificity in instructions and cue-word familiarity on prospective performance was examined. Exp. 1 was based on a typical prospective memory paradigm using familiar and unfamiliar cue words. Prospective memory performances under general and specific instruction conditions were compared. In Exp. 2, the relationship found in Exp. 1 was further investigated based on the activation of cue words and prospective memory performance. The experimental results indicated that, when a spontaneous retrieval process was used, unfamiliar cues were more likely to be detected, whereas when only strategic monitoring played a role, familiar cues were more likely to be detected, suggesting that retrieval varied systematically across experimental situations, as predicted by the multiprocess model.

We investigated output-monitoring errors in a modified source-monitoring paradigm. Unlike the traditional paradigm that involves two phases, learning and monitoring, the modified paradigm involves three phases, learning, enactment, and monitoring. Three experiments produced two major findings. First, compared with the traditional paradigm, the modified paradigm produced fewer monitoring errors. Second, performing a dual-task during the enactment phase increased monitoring errors for the items that participants repeatedly enacted during the learning phase. In contrast, performing a dual-task during the learning phase did not influence monitoring errors. It only decreased the number of items that were enacted during the enactment phase. We concluded that monitoring errors are more likely to occur (a) when the modality of items matches between the learning and enactment phases (i.e., items are enacted during both phases), and (b) when a dual-task increases processing demands during the enactment phase.