Attentional allocation and the pan-field color illusion.

Humans subjectively experience a scene as rendered in color across the entire visual field, a visual phenomenon called "pan-field color" (Balas & Sinha, 2007). This experience is inconsistent with the limited color sensitivity in the peripheral visual field. We investigated the effects of visual attention allocated to the peripheral visual field on the pan-field color illusion. Using "chimera" stimuli in which color was restricted to a circular central area, we assessed observers' tendency to perceive color throughout images with achromatized peripheral regions. We separately analyzed sensitivity and response bias in judging the color content of the scene image as full-color, chimera, or gray. Using a dual-task paradigm, we manipulated observers' attentional allocation by controlling the stimulus presentation time of the central task, making the foveal attentional load change. The slope of the foveal load-sensitivity function suggests that attention was modulated by foveal load even in the peripheral visual field. Bias was affected by the size of the central colored area, such that the tendency to answer "full-color" to the chimera image increased with eccentricity. Based on these effects of attention on sensitivity and bias, we suggest that the pan-field color illusion cannot be fully explained by the decrease of sensitivity that is modulated by attentional allocation in the periphery. Our results rather indicate that the pan-field color illusion at least partly reflects a liberal bias in peripheral vision.

Disconnected hand avatar can be integrated into the peripersonal space.

Several studies have shown that space immediately surrounding the body, or the peripersonal space is represented differently in the brain from the more distant extra-personal space. Moreover, the boundary of peripersonal space can be extended to space surrounding the tip of a tool held by the hand. However, it is not known if tools need to be connected to the body to modulate the peripersonal space. We used a line bisection task to investigate whether peripersonal space representation surrounds a virtual hand avatar that is disconnected from the body. Healthy participants conducted a line bisection task by responding with either a virtual hand avatar or a laser pointer. The to-be-bisected lines were presented either in peripersonal or extra-personal space. When the lines were placed in extra-personal space, the virtual hand avatar was presented near the line such that the hand avatar was far from participants and disconnected from their bodies. Results indicated a shift in the line bisection bias from the left to the right as the line presentation distance increased when using the laser pointer, whereas no shift in bias was observed when using the virtual hand avatar. This result indicates that objects resembling human hands presented even at a distance and disconnected from the body can be integrated into the peripersonal space, which suggests that peripersonal space representation is more flexible than previously reported.

Does response facilitation to visuo-tactile stimuli around a remote-controlled hand avatar reflect peripersonal space or attentional bias?

People react faster to visuo-tactile stimuli presented near the body (i.e., in peripersonal space) than to tactile stimuli presented alone. This multi-sensory facilitation effect has been used as a measurement of peripersonal space. Previous research has reported that peripersonal space representations can be modulated by actively using hand-held tools or disconnected hand avatars. However, previous research has ignored the possibility that the attentional effect of active tool use could affect multi-sensory facilitation. In the present study, we delivered tactile stimuli to participants' left or right hand concurrently with visual stimuli presented near a virtual hand avatar operated by the movements of participants' left or right hand, which was shown far in a virtual environment and disconnected from the body. Participants reacted to tactile stimuli while ignoring the visual stimuli. The results indicated a multi-sensory facilitation effect when tactile stimuli were delivered to the hand used to operate the hand avatar. In contrast, the facilitation was not observed when the tactile stimuli were delivered to the hand that is not operating the hand avatar. These results suggest that the strength of the multi-sensory facilitation effect differed across conditions, even though the visual attention captured around the hand avatar was controlled across conditions. We concluded that the modulation of peripersonal space resulting from using tools or avatars is nearly independent of visual attention captured around tools or avatars.

Consistency of synesthetic association varies with grapheme familiarity: A longitudinal study of grapheme-color synesthesia.

Grapheme-color synesthesia is a condition in which the visual perception of letters or numbers induces a specific color sensation. The consistency of grapheme-color association has been considered as a fundamental characteristic of synesthesia. However, recent studies have indicated that this association can change across the adult lifespan, and it has become necessary to investigate the factors behind the changes within each synesthete. We conducted a longitudinal study of Japanese adult synesthetes to investigate long-term (5-8 years) changes in color responses to 300 graphemes (alphanumeric and Japanese characters). Graphemes with lower long-term consistency of synesthetic association also tended to have lower short-term consistency, indicating that grapheme-color association's consistency is determined for each grapheme. Further, less familiar graphemes had less consistent associations with their synesthetic colors. These findings suggest that a stronger grapheme-color association is formed for more familiar graphemes, leading to the consolidation of synesthetic color for such graphemes.

Discounting mechanism underlies extinction illusion.

Humans can perceive a coherent visual scene despite a low spatial resolution in peripheral vision. How does the visual system determine whether an object exists in the periphery? We addressed this question by focusing on the extinction illusion in which a disk becomes subjectively invisible when presented at the intersection of grids. We hypothesized that the disk would go unnoticed when the stimuli with and without the disk produced the same strength of visual signals. The visual system would miss the disk by confounding the target signals with the intersection signals that should be discounted. Computational analysis revealed that the energy ratio between the stimuli with and without the disk decreased with stimulus eccentricity and such energy ratio could successfully explain the observer's d' to detect the disk. These results indicate that the discounting mechanism relying on stimulus energy determines the awareness toward a peripheral object.

Do the colors of your letters depend on your language? Language-dependent and universal influences on grapheme-color synesthesia in seven languages.

Grapheme-color synesthetes experience graphemes as having a consistent color (e.g., "N is turquoise"). Synesthetes' specific associations (which letter is which color) are often influenced by linguistic properties such as phonetic similarity, color terms ("Y is yellow"), and semantic associations ("D is for dog and dogs are brown"). However, most studies of synesthesia use only English-speaking synesthetes. Here, we measure the effect of color terms, semantic associations, and non-linguistic shape-color associations on synesthetic associations in Dutch, English, Greek, Japanese, Korean, Russian, and Spanish. The effect size of linguistic influences (color terms, semantic associations) differed significantly between languages. In contrast, the effect size of non-linguistic influences (shape-color associations), which we predicted to be universal, indeed did not differ between languages. We conclude that language matters (outcomes are influenced by the synesthete's language) and that synesthesia offers an exceptional opportunity to study influences on letter representations in different languages.

On the three-quarter view advantage of familiar object recognition.

A three-quarter view, i.e., an oblique view, of familiar objects often leads to a higher subjective goodness rating when compared with other orientations. What is the source of the high goodness for oblique views? First, we confirmed that object recognition performance was also best for oblique views around 30° view, even when the foreshortening disadvantage of front- and side-views was minimized (Experiments 1 and 2). In Experiment 3, we measured subjective ratings of view goodness and two possible determinants of view goodness: familiarity of view, and subjective impression of three-dimensionality. Three-dimensionality was measured as the subjective saliency of visual depth information. The oblique views were rated best, most familiar, and as approximating greatest three-dimensionality on average; however, the cluster analyses showed that the "best" orientation systematically varied among objects. We found three clusters of objects: front-preferred objects, oblique-preferred objects, and side-preferred objects. Interestingly, recognition performance and the three-dimensionality rating were higher for oblique views irrespective of the clusters. It appears that recognition efficiency is not the major source of the three-quarter view advantage. There are multiple determinants and variability among objects. This study suggests that the classical idea that a canonical view has a unique advantage in object perception requires further discussion.

The effect of expert knowledge on medical search: medical experts have specialized abilities for detecting serious lesions.

How does domain-specific knowledge influence the experts' performance in their domain of expertise? Specifically, can visual search experts find, with uniform efficiency, any type of target in their domain of expertise? We examined whether acquired knowledge of target importance influences an expert's visual search performance. In some professional searches (e.g., medical screenings), certain targets are rare; one aim of this study was to examine the extent to which experts miss such targets in their searches. In one experiment, radiologists (medical experts) engaged in a medical lesion search task in which both the importance (i.e., seriousness/gravity) and the prevalence of targets varied. Results showed decreased target detection rates in the low prevalence conditions (i.e., the prevalence effect). Also, experts were better at detecting important (versus unimportant) lesions. Results of an experiment using novices ruled out the possibility that decreased performance with unimportant targets was due to low target noticeability/visibility. Overall, the findings suggest that radiologists do not have a generalized ability to detect any type of lesion; instead, they have acquired a specialized ability to detect only those important lesions relevant for effective medical practices.

[The role of sustained attention in shift-contingent change blindness].

Previous studies of change blindness have examined the effect of temporal factors (e.g., blank duration) on attention in change detection. This study examined the effect of spatial factors (i.e., whether the locations of original and changed objects are the same or different) on attention in change detection, using a shift-contingent change blindness task. We used a flicker paradigm in which the location of a to-be-judged target image was manipulated (shift, no-shift). In shift conditions, the image of an array of objects was spatially shifted so that all objects appeared in new locations; in no-shift conditions, all object images of an array appeared at the same location. The presence of visual stimuli (dots) in the blank display between the two images was.manipulated (dot, no-dot) under the assumption that abrupt onsets of these stimuli would capture attention. Results indicated that change detection performance was improved by exogenous attentional capture in the shift condition. Thus, we suggest that attention can play an important role in change detection during shift-contingent change blindness.

Three-quarter view preference for three-dimensional objects in 8-month-old infants.

This study examined infants' visual perception of three-dimensional common objects. It has been reported that human adults perceive object images in a view-dependent manner: three-quarter views are often preferred to other views, and the sensitivity to object orientation is lower for three-quarter views than for other views. We tested whether such characteristics were observed in 6- to 8-month-old infants by measuring their preferential looking behavior. In Experiment 1 we examined 190- to 240-day-olds' sensitivity to orientation change and in Experiment 2 we examined these infants' preferential looking for the three-quarter view. The 240-day-old infants showed a pattern of results similar to adults for some objects, while the 190-day-old infants did not. The 240-day-old infants' perception of object view is (partly) similar to that of adults. These results suggest that human visual perception of three-dimensional objects develops at 6 to 8 months of age.

Pre- and post-head processing for single- and double-scrambled sentences of a head-final language as measured by the eye tracking method.

Using the eye-tracking method, the present study depicted pre- and post-head processing for simple scrambled sentences of head-final languages. Three versions of simple Japanese active sentences with ditransitive verbs were used: namely, (1) SO1O2V canonical, (2) SO2O1V single-scrambled, and (3) O1O2SV double-scrambled order. First pass reading times indicated that the third noun phrase just before the verb in both single- and double-scrambled sentences required longer reading times compared to canonical sentences. Re-reading times (the sum of all fixations minus the first pass reading) showed that all noun phrases including the crucial phrase before the verb in double-scrambled sentences required longer re-reading times than those required for single-scrambled sentences; single-scrambled sentences had no difference from canonical ones. Therefore, a single filler-gap dependency can be resolved in pre-head anticipatory processing whereas two filler-gap dependencies require much greater cognitive loading than a single case. These two dependencies can be resolved in post-head processing using verb agreement information.

Does cross-modal correspondence modulate modality-specific perceptual processing? Study using timing judgment tasks.

Cross-modal correspondences refer to associations between stimulus features across sensory modalities. Previous studies have shown that cross-modal correspondences modulate reaction times for detecting and identifying stimuli in one modality when uninformative stimuli from another modality are present. However, it is unclear whether such modulation reflects changes in modality-specific perceptual processing. We used two psychophysical timing judgment tasks to examine the effects of audiovisual correspondences on visual perceptual processing. In Experiment 1, we conducted a temporal order judgment (TOJ) task that asked participants to judge which of two visual stimuli presented with various stimulus onset asynchronies (SOAs) appeared first. In Experiment 2, we conducted a simultaneous judgment (SJ) task that asked participants to report whether the two visual stimuli were simultaneous or successive. We also presented an unrelated auditory stimulus, simultaneously or preceding the first visual stimulus, and manipulated the congruency between audiovisual stimuli. Experiment 1 indicated that the points of subjective simultaneity (PSSs) between the two visual stimuli estimated in the TOJ task shifted according to the audiovisual correspondence between the auditory pitch and visual features of vertical location and size. However, these audiovisual correspondences did not affect PSS estimated using the SJ task in Experiment 2. The different results of the two tasks can be explained through the response bias triggered by audiovisual correspondence that only the TOJ task included. We concluded that audiovisual correspondence would not modulate visual perceptual timing and that changes in modality-specific perceptual processing might not trigger the congruency effects reported in previous studies.

Auditory scene context facilitates visual recognition of objects in consistent visual scenes.

Visual object recognition is facilitated by contextually consistent scenes in which the object is embedded. Scene gist representations extracted from the scenery backgrounds yield this scene consistency effect. Here we examined whether the scene consistency effect is specific to the visual domain or if it is crossmodal. Through four experiments, the accuracy of the naming of briefly presented visual objects was assessed. In each trial, a 4-s sound clip was presented and a visual scene containing the target object was briefly shown at the end of the sound clip. In a consistent sound condition, an environmental sound associated with the scene in which the target object typically appears was presented (e.g., forest noise for a bear target object). In an inconsistent sound condition, a sound clip contextually inconsistent with the target object was presented (e.g., city noise for a bear). In a control sound condition, a nonsensical sound (sawtooth wave) was presented. When target objects were embedded in contextually consistent visual scenes (Experiment 1: a bear in a forest background), consistent sounds increased object-naming accuracy. In contrast, sound conditions did not show a significant effect when target objects were embedded in contextually inconsistent visual scenes (Experiment 2: a bear in a pedestrian crossing background) or in a blank background (Experiments 3 and 4). These results suggested that auditory scene context has weak or no direct influence on visual object recognition. It seems likely that consistent auditory scenes indirectly facilitate visual object recognition by promoting visual scene processing.

Synesthetic colors for Japanese late acquired graphemes.

Determinants of synesthetic color choice for the Japanese logographic script, Kanji, were studied. The study investigated how synesthetic colors for Kanji characters, which are usually acquired later in life than other types of graphemes in Japanese language (phonetic characters called Hiragana and Katakana, and Arabic digits), are influenced by linguistic properties such as phonology, orthography, and meaning. Of central interest was a hypothesized generalization process from synesthetic colors for graphemes, learned prior to acquisition of Kanji, to Kanji characters learned later. Results revealed that color choices for Kanji characters depend on meaning and phonological information. Some results suggested that colors are generalized from Hiragana characters and Arabic digits to Kanji characters via phonology and meaning, respectively. Little influence of orthographic information was observed. The findings and approach of this study contributes to a clarification of the mechanism underlying grapheme-color synesthesia, especially in terms of its relationship to normal language processing.

Pitch-elevation and pitch-size cross-modal correspondences do not affect temporal ventriloquism.

Temporal ventriloquism refers to the shift in the perceived timing of a visual stimulus towards a transient auditory stimulus presented close in time. This effect is demonstrated by greater sensitivity of temporal order judgments of two visual stimuli when a sound is presented before the first visual stimulus and after the second visual stimulus. Recent studies suggest that temporal ventriloquism is affected by cross-modal correspondence between auditory pitch and visual elevation but not by correspondence between pitch and visual size. Here we examined the possibility that these results do not reflect a difference in the effects of different types of cross-modal correspondences on temporal ventriloquism but are rather mediated by shifts in visual-spatial attention triggered by preceding auditory stimuli. In Experiment 1, we replicated the results of previous studies that varied with the type of correspondence. Experiment 2 investigated the effects of the second audiovisual stimuli's asynchrony while the first audiovisual stimuli were synchronized. The results, unlike in Experiment 1, revealed that the magnitude of the temporal ventriloquism effect did not change with the congruency of pitch-elevation correspondence. Experiment 3 also indicated that the asynchrony of the first audiovisual stimuli modulated visual discrimination sensitivity irrespective of temporal ventriloquism. These results suggest that cross-modal correspondences do not affect temporal ventriloquism. Greater visual sensitivity when audiovisual stimuli are congruent with pitch-elevation correspondence may be attributable to shifts in visual attention caused by pitches of the preceding auditory stimulus, which speeds up detection of the first visual stimulus.

Cross-modal correspondence between auditory pitch and visual elevation modulates audiovisual temporal recalibration.

Cross-modal correspondences refer to associations between feature dimensions of stimuli across sensory modalities. Research has indicated that correspondence between audiovisual stimuli influences whether these stimuli are integrated or segregated. On the other hand, the audiovisual integration process plastically changes to compensate for continuously observed spatiotemporal conflicts between sensory modalities. If and how cross-modal correspondence modulates the "recalibration" of integration is unclear. We investigated whether cross-modal correspondence between auditory pitch and visual elevation affected audiovisual temporal recalibration. Participants judged the simultaneity of a pair of audiovisual stimuli after an adaptation phase in which alternating auditory and visual stimuli equally spaced in time were presented. In the adaptation phase, auditory pitch and visual elevation were manipulated to fix the order within each pairing of audiovisual stimuli congruent with pitch-elevation correspondence (visual leading or auditory leading). We found a shift in the point of subjective simultaneity (PSS) between congruent audiovisual stimuli as a function of the adaptation conditions (Experiment 1, 2), but this shift in the PSS was not observed within incongruent pairs (Experiment 2). These results indicate that asynchronies between audiovisual signals congruent with cross-modal correspondence are selectively recalibrated.

Adaptation to delayed visual feedback of the body movement extends multisensory peripersonal space.

The space surrounding the body in which individuals interact with the environment is known as the peripersonal space (PPS). Previous studies have reported that PPS has multisensory nature. However, the relationship between the multisensory nature of PPS and an individuals' defensive actions has not been fully clarified to date. We investigated this relationship by examining the multisensory representation of PPS under situations in which visual feedback of body movements was delayed by using a virtual reality system. The results indicated that body-movement delays extended the multisensory PPS, suggesting that body-movement delays increased the potential threat of distant objects because it was necessary to prepare defensive actions sooner. The previous findings can be interpreted that PPS is modulated by the spatio-temporal relationship between people and external stimuli. This view may provide evidence of interactions between defensive and nondefensive functions of the multisensory PPS.

Synesthetic colors are elicited by sound quality in Japanese synesthetes.

Determinants of synesthetic color choice for Japanese phonetic characters were studied in six Japanese synesthetes. The study used Hiragana and Katakana characters, which represent the same set of syllables although their visual forms are dissimilar. From a palette of 138 colors, synesthetes selected a color corresponding to each character. Results revealed that synesthetic color choices for Hiragana characters and those for their Katakana counterparts were remarkably consistent, indicating that color selection depended on character-related sounds and not visual form. This Hiragana-Katakana invariance cannot be regarded as the same phenomenon as letter case invariance, usually reported for English grapheme-color synesthesia, because Hiragana and Katakana characters have different identities whereas upper and lower case letters have the same identity. This involvement of phonology suggests that cross-activation between an inducer (i.e., letter/character) brain region and that of the concurrent (i.e., color) area in grapheme-color synesthesia is mediated by higher order cortical processing areas.

Rapid extraction of gist from visual text and its influence on word recognition.

Two experiments explored rapid extraction of gist from a visual text and its influence on word recognition. In both, a short text (sentence) containing a target word was presented for 200 ms and was followed by a target recognition task. Results showed that participants recognized contextually anomalous word targets less frequently than contextually consistent counterparts (Experiment 1). This context effect was obtained when sentences contained the same semantic content but with disrupted syntactic structure (Experiment 2). Results demonstrate that words in a briefly presented visual sentence are processed in parallel and that rapid extraction of sentence gist relies on a primitive representation of sentence context (termed protocontext) that is semantically activated by the simultaneous presentation of multiple words (i.e., a sentence) before syntactic processing.

Remote hand: Hand-centered peripersonal space transfers to a disconnected hand avatar.

The space surrounding our body is called peripersonal space (PPS). It has been reported that visuo-tactile facilitation occurs more strongly within PPS than outside PPS. Furthermore, previous research has revealed several methods by which PPS can be extended. The present study provides the first behavioral evidence of the transfer of PPS in a virtual environment by a novel technique. PPS representation was investigated using a remote-controlled hand avatar presented far from the body in a virtual environment. Participants showed strongest visuo-tactile facilitation at the far space around the remote hand and no facilitation at the near space around the real hand, suggesting that PPS transfers from near the body to the space around the hand avatar. The present results extend previous findings of the plasticity of PPS and demonstrate flexibility of PPS representation beyond the physical and anatomical limits of body representation.