Illusory deformation of the finger is more extensive in the distal than the lateral direction.

Previous studies have examined the rubber hand illusion with finger lengthening, but there is limited research on finger widening. This suggests a strong cognitive bias toward the illusory expansion of the finger in a distal direction rather than lateral. To test this, we compared the illusory deformability of the finger in the distal and lateral directions through the generation of illusory finger deformation using a double-touch operation, referred to as the numbness illusion. Our results showed that perceived distal distortion was wholly superior to perceived lateral distortion in terms of sense of ownership ratings. Moreover, the extent of the perceived deformation was greater in the distal than lateral direction, supporting our hypothesis that there is a distal bias. We suggest that this preference may be because the presence of multiple joints is required to create illusory deformation in the target direction.

Diversity of aphantasia revealed by multiple assessments of visual imagery, multisensory imagery, and cognitive style.

Aphantasia-a condition wherein individuals have a reduced or absent construction of voluntary visual imagery-is diagnosed using either the Vividness of Visual Imagery Questionnaire (VVIQ) or self-identification. However, a significant discrepancy exists between the proportions of aphantasia in the populations assessed using these two criteria. It is unclear why the reported proportions differ excessively and what percentage of people cannot form visual imagery. We investigated the replicability of the proportion of people with aphantasia using both criteria in the same population of participants. Therefore, we explored the potential causes of the discrepancy and characteristics of putative aphantasia in terms of multisensory imagery, cognitive style, and face recognition ability. First, we conducted an online sampling study (Study 1: N = 2,871) using the VVIQ, self-identification of a reduction in visual imagery, Questionnaire upon Mental Imagery (QMI), and Verbalizer-Visualizer Questionnaire (VVQ). We found that 3.7 and 12.1% fulfilled the VVIQ and self-identification criteria, respectively, roughly replicating the proportions reported in previous studies. The self-identification criterion-but not the VVIQ criterion-contains items related to face recognition; hence, we suspected that face recognition ability was factor contributing to this discrepancy and conducted another online sampling study (Study 2: N = 774). We found a significant correlation between VVIQ and face recognition ability in the control group with self-identification, but not in the group defined by low VVIQ (VVIQ ≤32). As the participants in the control group with self-identification tended to exhibit moderately high VVIQ scores but low face recognition ability, we reason that the discrepancy can be partially explained by the contamination of individual differences in face recognition ability. Additional analyses of Study 1 revealed that the aphantasia group included participants who lacked all types of sensory imagery or only visual imagery in multisensory imagery and exhibited a non-specific cognitive style. This study indicates that the VVIQ alone may be insufficient to diagnose individuals who report an inability to form visual imagery. Furthermore, we highlight the importance of multiple assessments-along with the VVIQ-to better understand the diversity of imagery in aphantasia.

Multisensory perceptual distortion including auditory distortions in Alice in Wonderland syndrome: a case report.

Alice in Wonderland syndrome (AIWS) is a rare perceptual disorder characterized mainly by perceptual distortions of visual objects and one's own body. While there are many case reports of visual and somatosensory distortions associated with AIWS, little is known about auditory distortion. Therefore, we present the case of a 22-year-old right-handed woman who described having auditory as well as visual and somatosensory distortion experiences and a family history of AIWS. The subject reported experiencing multisensory perceptual distortions, where she sees other people's faces as larger and hears their voices as louder at the same time. This particular case suggests that auditory distortion - which contributes to constructing the perception of the surrounding space and the body - may also be characterized as a perceptual symptom of AIWS.

The Posture of Putting One's Palms Together Modulates Visual Motion Event Perception.

We investigated the effect of an observer's hand postures on visual motion perception using the stream/bounce display. When two identical visual objects move across collinear horizontal trajectories toward each other in a two-dimensional display, observers perceive them as either streaming or bouncing. In our previous study, we found that when observers put their palms together just below the coincidence point of the two objects, the percentage of bouncing responses increased, mainly depending on the proprioceptive information from their own hands. However, it remains unclear if the tactile or haptic (force) information produced by the postures mostly influences the stream/bounce perception. We solved this problem by changing the tactile and haptic information on the palms of the hands. Experiment 1 showed that the promotion of bouncing perception was observed only when the posture of directly putting one's palms together was used, while there was no effect when a brick was sandwiched between the participant's palms. Experiment 2 demonstrated that the strength of force used when putting the palms together had no effect on increasing bounce perception. Our findings indicate that the hands-induced bounce effect derives from the tactile information produced by the direct contact between both palms.

The neural correlates of biomechanical constraints in hand laterality judgment task performed from other person's perspective: A near-infrared spectroscopy study.

Previous studies, mainly using a first-person perspective (1PP), have shown that the judgments of the hand laterality judgment (HLJ) task are dependent on biomechanical constraints (BC). Specifically, differing reaction times (RT) for hand pictures rotated medially or laterally around the mid sagittal plane are attributed to the BC effect on motor imagery. In contrast, we investigated whether the HLJ task is also subject to BC when performed from a third-person perspective (3PP) as well as 1PP using near-infrared spectroscopy (NIRS) to measure the brain activity of prefrontal cortex (PFC) in right-handed participants assigned to 1PP or 3PP groups. The 1PP group judged whether a presented hand was their own left or right hand, and the 3PP group whether it was the other's left or right hand. Using their HLJ task error rates, the 1PP and 3PP groups were subdivided into an Error Group (EG) and No Error Group (NEG). For the 1PP group, both EG and NEG showed a significant Hand Laterality × Orientation interaction for RT, indicating the BC effect on motor imagery. For the 3PP group, however, neither EG nor NEG showed the interaction, even though EG showed a significantly longer RT than NEG. These results suggest that the 3PP EG appropriately followed the 3PP task instruction, while the NEG might have taken 1PP. However, the 3PP EG NIRS profile of left PFC showed a significant Hand Laterality × Orientation interaction, while the 1PP EG did not. More noteworthy is that the left PFC activation of EG showed an interaction between the 1PP and 3PP groups when the left hand was presented. Furthermore, in the NEG, the PFC activation was not influenced by the BC in either the 1PP or 3PP condition. These results indicate that BC interferes with the HLJ task performed from the 1PP and 3PP.

Inter-brain network underlying turn-based cooperation and competition: A hyperscanning study using near-infrared spectroscopy.

The present study examined neural substrates underlying turn-based cooperation and competition in a real two-person situation. We simultaneously measured pairs of participants' activations in their bilateral frontal, temporal, and parietal regions using a 96-channel near-infrared spectroscopy (NIRS) system, when participants played a turn-taking disk-game on a computer. NIRS data demonstrated significant inter-brain neural synchronization (INS) across participant pairs' right posterior superior temporal sulcus (pSTS) in both the cooperation and competition conditions, and the competition condition also involved significant INS in the right inferior parietal lobule (IPL). In addition, competitive dyads' INS in the bilateral inferior frontal gyrus (IFG) may play as a role of mediation in relationship between their empathy score and disk-manipulation latency, but cooperative dyads' INS did not. These results suggest that first the right pSTS may be commonly involved in both cooperation and competition due to task demands of joint attention and intention understanding, while the right IPL may be more important for competition due to additional requirements of mentalizing resources in competing contexts. Second, participants' empathy may promote INS in the bilateral IFG across competitors, and in turn affect their competitive performance.

Hand Positions Alter Bistable Visual Motion Perception.

We found that a hand posture with the palms together located just below the stream/bounce display could increase the proportion of bouncing perception. This effect, called the hands-induced bounce (HIB) effect, did not occur in the hands-cross condition or in the one-hand condition. By using rubber hands or covering the participants' hands with a cloth, we demonstrated that the visual information of the hand shapes was not a critical factor in producing the HIB effect, whereas proprioceptive information seemed to be important. We also found that the HIB effect did not occur when the participants' hands were far from the coincidence point, suggesting that the HIB effect might be produced within a limited spatial area around the hands.

Understand after like, viewer's delight? A fNIRS study of order-effect in combined hedonic and cognitive appraisal of art.

We investigate neural and behavioral aspects of the interrelation between 'liking' and 'understanding' when both appraisals are made within one judgment task. Our goal was to explore questions regarding how these appraisals combine, and specifically whether there is an order-effect when both are employed in sequence. To this end, we tested a hypothesis derived from new models in neuroaesthetics, and concerning processing of art, which suggest that perception may involve a natural sequence from first processing for hedonic quality (i.e., liking) followed by processing for understanding. Thus, due to the initial liking assessment's capacity to prime deepened cognitive involvement, a Liking-Understanding order may show key differences in final assessments or brain activation when compared to an Understanding-Liking sequence. Thirty-two participants evaluated a range of paintings, balanced for visual appeal and understandability, in a two-part task in which half evaluated for understanding followed by liking and the other half had question order reversed. Brain activity was recorded via functional Near Infrared Spectroscopy (fNIRS). Results showed no assessment interrelation or order effect in artwork evaluations. However, participants who began with evaluation for liking, and who came to incongruent combinations (i.e., "I like, but I don't understand" or "I don't like, but I understand"), showed significantly higher activation in left medial prefrontal cortex. This area is functionally associated with attention and integration of hedonic/informational elements. Findings provide tentative support for a liking-driven order-effect, as well as for physiological connection between appraisals, which may not appear in behavioral evidence, and suggest need for further consideration of this topic in appraisal research.