Hisato IMAI

Although it is well known that reward enhances learning and memory, how extensively such enhancement occurs remains unclear. To address this question, we examined how reward influences retrieval-induced forgetting (RIF) in which the retrieval of a nonpracticed item under the same category as a practiced item is worse than the retrieval of a nonpracticed item outside the category. Subjects were asked to try to encode category-exemplar pairs (e.g., FISH-salmon). Then, they were presented with a category name and a two-letter word stem (e.g., FISH-sa) and were asked to complete an encoded word (retrieval practice). For a correct response, apple juice was given as a reward in the reward condition and a beeping sound was presented in the no-reward condition. Finally, subjects were asked to report whether each exemplar had been presented in the first phase. RIF was replicated in the no-reward condition. However, in the reward condition, RIF was eliminated. These results suggest that reward enhances processing of retrieval of unpracticed members by mechanisms such as spreading activation within the same category, irrespective of whether items were practiced or not.

The subliminal mere exposure effect (SMEE) is the phenomenon wherein people tend to prefer patterns they have repeatedly observed without consciously identifying them. One popular explanation for the SMEE is that perceptual fluency within exposed patterns is misattributed to a feeling of preference for those patterns. Assuming that perceptual fluency is negatively correlated with the amount of mental effort needed to analyze perceptual aspects of incoming stimuli, pupil diameter should associate with SMEE strength since the former is known to reflect mental effort. To examine this hypothesis, we measured participants' pupil diameter during exposure to subthreshold stimuli. Following exposure, a preference test was administered. Average pupil diameter throughout exposure was smaller when the SMEE was induced than when the SMEE was not induced. This supports the hypothesis that increasing perceptual fluency during mere exposure modulates autonomic nervous responses, such as pupil diameter, and eventually leads to preference.

The subliminal mere exposure effect is a psychological phenomenon where people tend to prefer stimuli that they have been subliminally exposed to even if they cannot recognize the observed stimuli. One explanation for this effect is that the resulting perceptual fluency is misattributed to a feeling of preference. Thus, an increased perceptual fluency should correspond to decreased invested mental effort. Because the pupil constricts as mental effort decreases, we predict that if perceptual fluency does induce a preference for the exposed stimulus, then participants showing pupil constriction during subliminal exposure will exhibit the mere exposure effect later. To examine our hypothesis, we measured the pupil diameter while participants were visually exposed to subliminal stimuli. After exposure, participants judged their preferences to the stimuli. We found that pupil diameter during subliminal exposure was significantly smaller for participants who later exhibited the mere exposure effect, suggesting that perceptual fluency may be the underlying mechanism of the subliminal mere exposure effect.

This study examines whether the involuntary recollection of an autobiographical memory elicited from an odor cue is determined by cue identifiability, emotional valence, or frequency of everyday encounters. After a semantic-differential (SD) task for various odors, participants (N=74) were asked about occurrences of involuntary recollections during the SD task. The results revealed that more frequently encountered odors were more likely to trigger involuntary recollections. However, no effects were observed for identifiability or emotional valence. These findings suggest that odor cues induce involuntary recollections in a non-verbal manner and that the process of involuntary recollection varies according to cue type.

We investigated whether audiovisual synchrony perception for speech could change after observation of the audiovisual temporal mismatch. Previous studies have revealed that audiovisual synchrony perception is re-calibrated after exposure to a constant timing difference between auditory and visual signals in non-speech. In the present study, we examined whether this audiovisual temporal recalibration occurs at the perceptual level even for speech (monosyllables). In Experiment 1, participants performed an audiovisual simultaneity judgment task (i.e., a direct measurement of the audiovisual synchrony perception) in terms of the speech signal after observation of the speech stimuli which had a constant audiovisual lag. The results showed that the "simultaneous" responses (i.e., proportion of responses for which participants judged the auditory and visual stimuli to be synchronous) at least partly depended on exposure lag. In Experiment 2, we adopted the McGurk identification task (i.e., an indirect measurement of the audiovisual synchrony perception) to exclude the possibility that this modulation of synchrony perception was solely attributable to the response strategy using stimuli identical to those of Experiment 1. The characteristics of the McGurk effect reported by participants depended on exposure lag. Thus, it was shown that audiovisual synchrony perception for speech could be modulated following exposure to constant lag both in direct and indirect measurement. Our results suggest that temporal recalibration occurs not only in non-speech signals but also in monosyllabic speech at the perceptual level.

Recent studies have shown that audiovisual synchrony is recalibrated after exposure to asynchronous auditory and visual signals. This temporal recalibration has been shown only under a dual-task situation for speech signals. Here we examined whether the temporal recalibration occurs for audiovisual speech in a single-task situation using an offline adaptation method. In the experiment, participants were exposed to synchronous or asynchronous audiovisual syllables (either congruent or incongruent) for 3 min. The adaptation phase was followed by test trials, in which participants judged whether the auditory or visual stimulus was presented first. Results showed shifts in the point of subjective simultaneity and the sensitivity. Our results suggest that attention to adaptation stimuli is necessary to induce temporal recalibration for speech. NeuroReport 22:684-688 (C) 2011 Wolters Kluwer Health | Lippincott Williams & Wilkins.

Anxious individuals have been shown to interpret others' emotional states negatively. Since most studies have used facial expressions as emotional cues, we examined whether trait anxiety affects the recognition of emotion in a dynamic face and voice that were presented in synchrony. The face and voice cues conveyed either matched (e.g., happy face and voice) or mismatched emotions (e.g., happy face and angry voice). Participants with high or low trait anxiety were to indicate the perceived emotion using one of the cues while ignoring the other. The results showed that individuals with high trait anxiety were more likely to interpret others' emotions in a negative manner, putting more weight on the to-be-ignored angry cues. This interpretation bias was found regardless of the cue modality (i.e., face or voice). Since trait anxiety did not affect recognition of the face or voice cues presented in isolation, this interpretation bias appears to reflect an altered integration of the face and voice cues among anxious individuals.

Perceptual asymmetries for tasks involving aesthetic preference or line bisection can be affected by asymmetrical neurological mechanisms or left/right reading habits. This study investigated the relative contribution of these mechanisms in 100 readers of Japanese and English. Participants made aesthetic judgments between pairs of mirror-reversed pictures showing: (a) static objects, (b) moving objects and (c) landscapes. A line bisection task was also administered. There was a strong effect of reading direction for static and mobile objects whereby Japanese readers preferred objects with a right-to-left directionality (and vice versa for English readers). In contrast, similar patterns were observed for the Japanese and English readers for the landscape and line bisection tasks. The results show that reading habits affect aesthetic judgments for static and moving object tasks, but not the landscape and line bisection tasks. The difference between the tasks may be related to the horizontal/vertical geometry of the stimuli, which makes the landscape and line bisection tasks more prone to universal effects related to cerebral dominance. (C) 2010 Elsevier Inc. All rights reserved.

Cultural differences in emotion perception have been reported mainly for facial expressions and to a lesser extent for vocal expressions. However, the way in which the perceiver combines auditory and visual cues may itself be subject to cultural variability. Our study investigated cultural differences between Japanese and Dutch participants in the multisensory perception of emotion. A face and a voice, expressing either congruent or incongruent emotions, were presented on each trial. Participants were instructed to judge the emotion expressed in one of the two sources. The effect of to-be-ignored voice information on facial judgments was larger in Japanese than in Dutch participants, whereas the effect of to-be-ignored face information on vocal judgments was smaller in Japanese than in Dutch participants. This result indicates that Japanese people are more attuned than Dutch people to vocal processing in the multisensory perception of emotion. Our findings provide the first evidence that multisensory integration of affective information is modulated by perceivers' cultural background.

Recent studies have shown that the audio-visual synchrony is recalibrated after adaptation to a constant timing difference between auditory and visual signals (i.e. temporal recalibration). Here we investigated whether the temporal recalibration occurs for audio-visual speech using an off-line adaptation method. After 3 minutes of lag observation, the audio-visual synchrony is recalibrated toward the adapted lag. The point of subjective simultaneity shifted after 10 seconds of lag observation, whereas the just noticeable difference did not change during this short observation period. The width of the temporal window extended only to the direction of audio delay. These findings extend the findings in previous studies and suggest different properties of temporal recalibration in speech.

In this article, we report on an experimental investigation of the spontaneous, uncued recall of prospective memories (memories for activities to be performed at a later time). Einstein & McDaniel (1990) developed an experimental paradigm for investigating prospective memory, in which participants were required to perform both an ongoing task (e.g., remembering words presented on the PC screen) and a prospective memory task (e.g., pressing a designated key whenever they saw a particular word, such as rake). They also claimed that there are two types of prospective memory: one is event-based prospective memory recall, which is triggered by another event ("I will give a message to John when I meet him"), and the other is time-based prospective memory recall, which is to be done after a particular period of time has elapsed (I will call Mary in 30 minutes") or at a certain time ("I will watch TV at 7:00 PM"). We examine the nature of the Einstein and McDaniel's paradigm and show that several important aspects of prospective memory have been left unstudied; specifically, spontaneous, uncued recall. We consider that it is caused by the cue-oriented nature of the paradigm. Furthermore, considering the prospective memory function in our everyday life, we cast doubt of the validity of the dissociation between time-based and event-based prospective memory. To investigate these two issues, we conducted a task-content oriented experiment which was a refined version of Einstein and McDaniel's paradigm. Thirteen undergraduates (9 male and 4 female) were presented 4 photographs on the PC screen simultaneously, and were required to judge which one of these four belonged to a different category (ongoing task). They were also required to stop the ongoing task when a photograph of envelopes was presented during the ongoing task and to call the experimenter in order to answer a questionnaire in an envelope before the experiment finished. Six participants were randomly assigned to an uncued condition, in which the photograph of envelopes was not actually presented (a photograph of a compass was presented instead) and 7 participants to a cued condition. The result showed that, although the expected recall cue was not presented, all the participants in uncued condition spontaneously remembered the prospective memory task. Furthermore, it was revealed that spontaneous recall did not occur randomly; instead, it frequently occurred near the end of the ongoing task, which is similar to the U-shaped clock-checking curve in the time-based prospective memory research (Ceci et al., 1988). These results suggest that participants in the uncued condition performed their event-based prospective memory task as a time-based one, and support our claim that prospective memory has both a time-based and event-based nature.

We conducted a visual search experiment in which participants detected a target (a moving natural image) which moves in the opposite direction to the other distractor images. A set size effect, that is, decrease of accuracy as the number of stimuli in the display increased, was observed. In another experiment to identify a factor that restricted the participants' performance in the task, we used moving random-dot patterns having various amount of relative motion. We found that a target with zero relative motion did pop-out, but the accuracy decreased as the amount of relative motion increased. We estimated the strength of the relative motion of the moving natural images based on the motion-energy model, and found a negative correlation between the accuracy and the strength of relative motion in the natural images. These results suggest that the relative motion is the primary factor for a visual search of moving natural images based on direction information.

Several previous studies on the misleading information effect employed priming tasks to examine the presence/ absence of original information. Given hyperspecificity of priming, however, it is questionable whether or not their priming tasks were sensitive enough to detect original information because their stimuli were perceptually different from the slides in the study phase. In the priming task of this research, we used slides whose perceptual properties were equivalent to those of the studied ones. In addition, we also conducted a yes-no recognition task using the same slides so that the results of these two tasks could be directly compared. The misleading information effect was replicated in the recognition task. Nevertheless, participants correctly recognized the original slides, whereas no priming effect was observed for those slides. These results suggest that although the original information survives the misleading information effect, its representation is modified so that only the yes-no recognition task, not the priming task, has access to it.

We conducted two experiments to specify the properties of the representation underlying perceptual priming. We transformed a particular property of stimuli between study and test. We used novel stimuli to eliminate contamination by semantic memory. They were rotated by 0 degrees, 90 degrees, or 180 degrees in Experiment 1 and were distorted horizontally in Experiment 2. These transformations were chosen for topological structures of stimuli to be kept unchanged. In Experiment 1 the priming effect of the rotated stimuli was smaller than that of the identical ones. The rotational angles had no effect. More surprisingly, the horizontally distorted stimuli showed the same amount of priming as the identical ones in Experiment 2. In contrast, recognition performance of the rotated or horizontally distorted stimuli was lower than that of the identical ones. Statistical independence between priming and recognition was found in both experiments. Thus, recognition was statistically and functionally independent of priming. These results suggest that the priming representation encodes both orientation-independent and orientation-dependent information, and that the global topological structure is critical for priming.

Three priming experiments were conducted to investigate associative and syntactic information processing in the Japanese language. Unlike in English, associative relation and syntactic plausibility can be manipulated independently. Subjects were given either a lexical decision or naming task because previous studies suggest that these tasks are sensitive to different processing stages. Two prime-target SOAs, 250 ms and 700 ms, were used. The results revealed that syntactic plausibility of associated prime-target pairs was processed differently from that of unassociated ones. When prime-target pairs were unassociated, syntactic plausibility priming was found with the 700 ms SOA in the lexical decision task, but no priming was found in the naming task. This result supports the previous claim that syntactic information is processed post-lexically. In contrast, when prime-target pairs were associated, syntactic plausibility priming was found both with 250 ms and 700 ms SOAs not only in the lexical decision but in the naming task. This suggests that syntactic plausibility of associated prime-target pairs is processed at the lexical rather than post-lexical stage.