To the next decade and beyond.

Sebastian Ocklenburg and colleagues have written an important and exciting summary of where laterality research might go. Perhaps reiterating some of their points, it seems important to understand the nuances of laterality. Laterality research can fall into the trap of "dichotomania" - where all laterality is seen in terms of left versus right. However, important insights can also be gained by examining the strength of laterality as well as the cooperation and competition between the hemispheres. Care also needs to be taken when examining individual differences between left- and right-handers. Studies, which may suffer from type 1 errors, often stigmatise left-handers with a host of negative traits. Pre-registration and the reporting of effect size may eliminate this bias.

The effect of cognitive load on horizontal and vertical spatial asymmetries.

Healthy individuals typically show a leftward attentional bias in the allocation of spatial attention along the horizontal plane, a phenomenon known as pseudoneglect, which relies on a right hemispheric dominance for visuospatial processing. Also, healthy individuals tend to overestimate the upper hemispace when orienting attention along the vertical plane, a phenomenon that may depend on asymmetric ventral and dorsal visual streams activation. Previous research has demonstrated that when attentional resources are reduced due to increased cognitive load, pseudoneglect is attenuated (or even reversed), due to decreased right-hemispheric activations. Critically, whether and how the reduction of attentional resources under load modulates vertical spatial asymmetries has not been addressed before. We asked participants to perform a line bisection task both with and without the addition of a concurrent auditory working memory task with lines oriented either horizontally or vertically. Results showed that increasing cognitive load reduced the typical leftward/upward bias with no difference between orientations. Our data suggest that the degree of cognitive load affects spatial attention not only in the horizontal but also in the vertical plane. Lastly, the similar effect of load on horizontal and vertical judgements suggests these biases may be related to only partially independent mechanisms.

Cognitive load exacerbates rightward biases during computer maze navigation.

Neurologically healthy individuals exhibit subtle attentional asymmetries, such that attention is preferentially directed leftwards for objects in near space and rightwards for objects in far space. These attentional biases also affect navigation and cause people to deviate to the right when passing through an aperture. The current study examined whether the rightward deviations observed in real-world environments translate to simulated environments. As proof of concept and to determine whether rightward biases could be further exacerbated, the degree of cognitive load imposed on participants was manipulated. Experiment 1 asked participants to navigate through the centre of a computer-based doorway. In one block of trials, participants completed the task by itself (baseline condition), while in another block of trials they also completed a simple auditory discrimination task (load condition). While analyses revealed rightward biases for both conditions, the difference between conditions was not significant. Experiment 2 therefore increased the difficulty of the auditory task. Analyses revealed a significant difference between conditions, suggesting that the degree of cognitive load further exacerbates rightward biases, demonstrating that the rightward asymmetries in navigation observed in the real world generalises to a simulated environment and that this phenomenon behaves in a way that is consistent with pseudoneglect.

Flowers in the Attic: Lateralization of the detection of meaning in visual noise.

The brain is a slave to sense; we see and hear things that are not there and engage in ongoing correction of these illusory experiences, commonly termed pareidolia. The current study investigates whether the predisposition to see meaning in noise is lateralized to one hemisphere or the other and how this predisposition to visual false-alarms is related to personality. Stimuli consisted of images of faces or flowers embedded in pink (1/f) noise generated through a novel process and presented in a divided-field paradigm. Right-handed undergraduates participated in a forced-choice signal-detection task where they determined whether a face or flower signal was present in a single-interval trial. Experiment 1 involved an equal ratio of signal-to-noise trials; experiment 2 provided more potential for illusionary perception with 25% signal and 75% noise trials. There was no asymmetry in the ability to discriminate signal from noise trials (measured using d') for either faces and flowers, although the response criterion (c) suggested a stronger predisposition to visual false alarms in the right visual field, and this was negatively correlated to the unusual experiences dimension of schizotypy. Counter to expectations, changing the signal-image to noise-image proportion in Experiment 2 did not change the number of false alarms for either faces and flowers, although a stronger bias was seen to the right visual field; sensitivity remained the same in both hemifields but there was a moderate positive correlation between cognitive disorganization and the bias (c) for "flower" judgements. Overall, these results were consistent with a rapid evidence-accumulation process of the kind described by a diffusion decision model mediating the task lateralized to the left-hemisphere.

Is trustworthiness lateralized in the face? Evidence from a trust game.

A turn of the head can be used to convey or conceal emotion, as the left side of the face is more expressive than the right. As the left cheek moves more when smiling, the present study investigated whether perceived trustworthiness is lateralized to the left cheek, using a trust game paradigm. In Experiment 1, participants were asked to share money with male and female "virtual partners." Left-left or right-right composite faces were used to represent the partners. There were no differences in the amount shared based on composite face, suggesting trustworthiness is not lateralized in the face. However, there was a robust effect whereby female partners were perceived to be significantly more trustworthy than males. In Experiment 2, the virtual partners presented either the left or the right cheek prominently. As in Experiment 1, the amount shared with the partners did not change depending on the cheek presented. Interestingly, female partners were again sent significantly more money than males. We found no support for lateralized trustworthiness in the face, suggesting that asymmetries in the face are not large enough to influence trustworthiness judgements. Instead, more stable facial features, such as sex-typical characteristics, appear to influence perceived trustworthiness.

Emotion processing in persons who respond vicariously towards others in pain: Disinhibited left-lateralized neural activity for threatening expressions.

We investigated emotional processing in vicarious pain (VP) responders. VP responders report an explicit sensory and emotional feeling of pain when they witness another in pain, which is greater in magnitude than the empathic processing of pain in the general population. In Study 1, 31 participants completed a chimeric faces task, judging whether emotional chimera in the left, or right, visual field was more intense. VP responders took longer to judge emotionality than non-responders, and fixated more on the angry hemiface in the right visual field, whereas non-responder controls had no lateralized fixation bias. In Study 2, blood-oxygen level-dependent signals were recorded during an emotional face matching task. VP intensity was correlated with increased insula activity and reduced middle frontal gyrus activity for angry faces, and with reduced activity in the inferior and middle frontal gyri for sad faces. Together, these findings suggest that VP responders are more reactive to negative emotional expressions. Specifically, emotional judgements involved altered left-hemisphere activity in VP responders, and reduced engagement of regions involved in emotion regulation.

The effect of cerebral asymmetries and eye scanning on pseudoneglect for a visual search task.

Pseudoneglect is the tendency for the general population to over-attend to the left. While pseudoneglect is classically demonstrated using line bisection, it also occurs for visual search. The current study explored the influence of eye movements and functional cerebral asymmetry on asymmetries for visual search. In Experiment 1, 24 participants carried out a conjunction search for a target within a rectangular array. A leftward advantage for detecting targets was observed when the eyes were free to move, but not when they were restricted by short exposure durations. In Experiment 2, the effect of functional cerebral asymmetry was explored by comparing 20 right-handers and 19 left-handers. Results showed a stronger leftward bias for the right-handers, consistent with a mechanism related to cerebral asymmetry. In Experiment 3, an eye-tracker directly controlled eye movements in 25 participants. A leftward advantage emerged when the eyes were still, but not when they were free to move. Experiments 1 and 3 produced contradictory results in relation to eye movements, which may be related to task-related demands. On balance, the data suggest that asymmetries in visual search can occur in the absence of eye movements and that they are related to right hemisphere specialisation for spatial attention.

The influence of distractors and numerical direction on mental number line bisection.

Spatial relationships are used to mentally represent numerical information. We visualize small numbers on the left and large numbers on the right, forming a mental number line. When determining the midpoint between two numbers, healthy participants show a bias to the left, similar to the bias on line bisection. Upper space distractors increase leftward line bisection biases and the current study examined the influence of distractors on mental number line bisection. Participants viewed sequential number triplets, presented concurrently with distractors. In Experiment 1, participants performed more accurately when numbers were presented in ascending order and showed stronger left biases for descending trials. Further, a responding bias was observed, where participants pressed the response key on the same side as the distractors. In Experiment 2, an orthogonal response mapping was used, which confirmed the occurrence of a responding bias. Interestingly, distractors weakened pseudoneglect, demonstrating a dissociation between line bisection and mental number line bisection in terms of distractibility. Numerical direction influenced asymmetries, such that leftward biases were stronger on descending trials. It is suggested that a right-to-left orientation of attention on descending trials might lead participants to overestimate how far along the number line they have moved, which increases leftward biases.

Hemispheric asymmetries in perceived depth revealed through a radial line bisection task.

Research suggests that the left cerebral hemisphere is predisposed for processing stimuli in 'near' space, whereas the right hemisphere is specialised for processing stimuli in 'far' space. This hypothesis was tested directly by asking 25 undergraduates to carry out a landmark radial line bisection task. To test the effect of hemispheric differences in processing, the lines were placed to the left, right or centre within the transverse plane. Consistent with predictions, lines in all three conditions were bisected distal to the true centre. More importantly, there was an asymmetry whereby the distal bias was stronger for lines presented in the left hemispace compared to the right hemispace. The results demonstrate that the perception of depth is affected by left/right placement along the lateral axis and highlight the cognitive/neural interplay between the radial and lateral axes.

Representational pseudoneglect for detecting changes to Rey-Osterrieth figures.

When dividing attention between the left and right sides of physical space, most individuals pay slightly more attention to the left side. This phenomenon, known as pseudoneglect, may also occur for the left and right sides of mental representations of stimuli. Representational pseudoneglect has been shown for the recall of real-world scenes and for simple, briefly presented stimuli. The current study sought to investigate the effect of exposure duration and complexity using adaptations of the Rey-Osterrieth figures. Undergraduates (n = 97) were shown a stimulus for 20 s and asked to remember it. Participants were then shown a probe and indicated whether it was the same or different. Results showed that, irrespective of whether an element was added or subtracted, changes on the left side of the remembered image were better detected. These results are consistent with representational pseudoneglect and demonstrate that this effect occurs for complex stimuli when presented for an extended period of time. Representation neglect is therefore unlikely to be the result of an initial saccade to the left-but could be related to the formation or recall of the representation.

End of the line: Line bisection, an unreliable measure of approach and avoidance motivation.

Approach motivation leads to greater left hemisphere activation, whereas an avoidant motivational state activates the right hemisphere. Recent research, which served as the basis for the current experiment, suggests line bisection provides a simple measure of approach/avoidance lateralisation. Findings from Experiment 1 indicated that the landmark task was sensitive enough to identify lateral asymmetries evoked by happy and angry faces; however, follow-up experiments failed to replicate this finding. When task instructions were slightly modified or when a mixed design was used, motivation did not influence landmark task performance. The use of images in lieu of faces also failed to produce a significant effect. Importantly, a straight replication of Experiment 1 produced a null result. Line bisection does not appear to be a suitable measure of lateralised approach/avoidance biases, possibly due to the high individual variability inherent in visuospatial biases. Implications for null hypothesis significance testing are also discussed.

A study on the natural history of scanning behaviour in patients with visual field defects after stroke.

BACKGROUND: A visual field defect (VFD) is a common consequence of stroke with a detrimental effect upon the survivors' functional ability and quality of life. The identification of effective treatments for VFD is a key priority relating to life post-stroke. Understanding the natural evolution of scanning compensation over time may have important ramifications for the development of efficacious therapies. The study aims to unravel the natural history of visual scanning behaviour in patients with VFD. The assessment of scanning patterns in the acute to chronic stages of stroke will reveal who does and does not learn to compensate for vision loss. METHODS/DESIGN: Eye-tracking glasses are used to delineate eye movements in a cohort of 100 stroke patients immediately after stroke, and additionally at 6 and 12 months post-stroke. The longitudinal study will assess eye movements in static (sitting) and dynamic (walking) conditions. The primary outcome constitutes the change of lateral eye movements from the acute to chronic stages of stroke. Secondary outcomes include changes of lateral eye movements over time as a function of subgroup characteristics, such as side of VFD, stroke location, stroke severity and cognitive functioning. DISCUSSION: The longitudinal comparison of patients who do and do not learn compensatory scanning techniques may reveal important prognostic markers of natural recovery. Importantly, it may also help to determine the most effective treatment window for visual rehabilitation.

Visual asymmetries for relative depth judgments in a three-dimensional space.

Our ability to process information about an object's location in depth varies along the horizontal and vertical axes. These variations reflect functional specialisation of the cerebral hemispheres as well as the ventral/dorsal visual streams for processing stimuli located in near and far space. Prior research has demonstrated visual field superiorities for processing near space in the lower and right hemispaces and for far space in the upper and left hemispaces. No research, however, has directly tested whether the functional specialisation of the visual fields actually makes objects look closer when presented in the lower or right visual fields. To measure biases in the perception of depth, we employed anaglyph stimuli where participants made closer/further judgments about the relative location of two spheres in a three-dimensional virtual space. We observed clear processing differences in this task where participants perceived the right and lower spheres to be closer and the left and upper spheres to be further away. Furthermore, no relationship between the horizontal and vertical dimensions was observed suggesting separate cognitive/neural mechanisms. Not only does this methodology clearly demonstrate differences in perceived depth across the visual field, it also opens up many possibilities for studying functional asymmetries in three-dimensional space.

Asymmetries in attention as revealed by fixations and saccades.

Neurologically normal individuals devote more attention to the left side; an asymmetry known as pseudoneglect, which reflects right hemisphere involvement in visuospatial attention. The role of eye movements in attentional asymmetries has received little consideration, particularly in terms of the greyscales task. Stimulus length, elevation, and presentation duration were manipulated, while monitoring eye movements during the greyscales task. Region of interest analyses compared time spent examining each quadrant of the stimulus. Further, saccades were examined in conjunction with fixations to gain an understanding of overall eye movement patterns. Scatterplots combining x-and y-coordinates illustrate mean eye position. Results demonstrated a comparison strategy was used, where the dark portions of each rectangle were fixated. Mean eye position was within the lower left quadrant. The left visual field was inspected most for the baseline condition. Interestingly, the lower visual field was examined most when duration, length, or elevation was manipulated. Eye movement patterns provide a possible explanation for why correlations are y not observed between visuospatial tasks. Different strategies, based on specific-task demands, are likely to be used, which in turn, engage separate aspects of visuospatial attention.

Close to me: the effect of asymmetrical environments on spatial attention.

Attention can be captured by distractors and can affect performance. To examine whether asymmetrical distractors, such as a wall, affect spatial attention, Experiment 1 required participants (n = 20) to determine the relative length of pre-bisected lines when a temporary barrier was placed close to the left or right sides of the display. Post-hoc tests showed that attention was drawn towards left, but not right, walls. Experiment 2 (n = 18) sought to increase this effect using a solid brick wall rather than a temporary barrier. Instead of strengthening the result, no effect of barrier was observed. A non-effect was also observed in Experiment 3 (n = 18) when participants moved a cursor to the line's middle. Finally, Experiment 4 (n = 26) showed that asymmetrical barriers had no effect on visual search. While the data showed some evidence that attention is distracted by walls placed to the left, this effect is weak and task-specific. PRACTITIONER SUMMARY: The ability to monitor critical information on displays can be affected by asymmetrical distractors. In many workplaces, a display may be placed alongside a wall. This study explored whether a wall placed to the left/right affects spatial attention. A weak, task-specific, attraction effect was observed for walls on the left.

[A Japanese version of the FLANDERS handedness questionnaire].

Quantitative assessment of handedness is required in various clinical and research settings in psychology, neuroscience, and medicine. In the present study we tested the reliability and validity of a Japanese version of the FLANDERS handedness questionnaire, which was a new measure of skilled hand preference originally reported by Nicholls, Thomas, Loetscher, and Grimshaw (2013). Participants (N=431) completed three types of handedness questionnaires: the FLANDERS handedness questionnaire, Edinburgh Handedness Inventory, and H · N handedness test. Factor analysis revealed that the Japanese version of FLANDERS handedness questionnaire had a single-factor structure and high internal consistency. This questionnaire also posssed high test-retest reliability and criterion-referenced validity. These results indicate that the Japanese version of the FLANDERS handedness questionnaire is a valid and useful measure of skilled hand preference for Japanese participants.

An investigation of inattentional blindness using gaze and frequency tagging.

Inattentional blindness (IB) occurs when a salient object presented in plain sight goes unnoticed when its appearance is unexpected. Across two experiments, participants completed a classic dynamic IB task while eye movements and steady-state visual evoked potential (SSVEP) responses were continually recorded. This allowed us to measure the modulation of gaze and brain-based indices of attention during IB. While an SSVEP response to all stimuli including the unexpected object was attained, only gaze measures were able to discriminate noticers from nonnoticers. Experiment 1 used a prototypical sustained IB task and found that gaze toward the unexpected object was largely unrelated to noticing that object. Experiment 2 manipulated the contrast of the target and distractor stimuli, and instead observed a tight concordance between gazing at the unexpected object and reporting its presence. This task-based variability in gaze deployment is consistent with the broader literature and cumulatively delineates the challenges faced in translating lab-based IB research from the bench to the bedside. (PsycInfo Database Record (c) 2023 APA, all rights reserved).

Central fixations with rightward deviations: saccadic eye movements on the landmark task.

Neurologically normal individuals show an attentional bias toward the left side, which results from right hemisphere activation during visuospatial tasks. The strength of this bias is influenced by various factors, such as line length, vertical elevation and presentation time. What remains unknown is how participants gather information via saccadic eye movements during task performance and how this relates to their responses. Eye movements were recorded while participants performed the landmark task. Fixations and saccades were both analysed to gain a complete understanding of eye movement patterns. Fixations tended to focus on the centre of the line, with few left-right differences. Saccades were examined by creating histograms illustrating all x-coordinates which were examined over the course of each trial. Interestingly, mean eye position varied with participant response, with an overall tendency to look to the right of centre. Results are consistent with prior research, which has primarily looked at fixations and demonstrates the necessity of examining saccades as well as fixations in order to see how eye movement patterns relate to pseudoneglect.

Paralyzed by desire: a new type of body integrity identity disorder.

BACKGROUND: Body incongruity in body integrity identity disorder (BIID) manifests in the desire to have a healthy limb amputated. We describe a variant of the disorder: the desire to become paralyzed (paralysis-BIID). METHOD: Sixteen otherwise healthy participants, recruited through Internet-based forums, websites, or word of mouth, completed questionnaires about details of their desire and accompanying symptoms. RESULTS: Onset of the desire for paralysis typically preceded puberty. All participants indicated a specific level for desired spinal cord injury. All participants simulated paralysis through mental imagery or physical pretending, and 9 (56%) reported erotic interest in paraplegia and/or disability. Our key new finding was that 37.5% of paralysis-BIID participants were women, compared with 4.4% women in a sample of 68 individuals with amputation-BIID. CONCLUSIONS: BIID reflects a disunity between self and body, usually with a prominent sexual component. Sex-related differences are emerging: unlike men, a higher proportion of women desire paralysis than desire amputation, and, while men typically seek unilateral amputation, women typically seek bilateral amputation. We propose that these sex-related differences in BIID manifestation may relate to sex differences in cerebral lateralization, or to disruption of representation and/or processing of body-related information in right-hemisphere frontoparietal networks.

A generalized magnitude system for space, time, and quantity? A cautionary note.

We investigated the claim that larger stimuli are perceived to last longer (Xuan, Zhang, He, & Chen, 2007). This claim, along with other similar claims of interactions between magnitude representations, is frequently used to support the generalized magnitude system hypothesis-the suggestion that the brain represents information about different magnitudes (e.g., time, space, and quantity) via a common mechanism. It is not clear, however, whether the size of a stimulus genuinely affects the perceived duration of the stimulus or simply biases decisions about duration. This was addressed using duration "equality judgments," which have been proposed to measure perceived duration unconfounded by decisional bias-in contrast to "comparative judgments," which are generally considered bias-prone. Using equality judgments, we failed to find support for the claim that larger stimuli are perceived to last longer, despite replicating the original effect reported by Xuan et al. (2007) using comparative judgments. Instead, unexpectedly, larger stimuli were judged-though not necessarily perceived-as shorter in duration. This result casts doubt on the conclusions of a significant body of behavioral interference studies using comparative judgments, which support a generalized magnitude system. We also identify a hitherto unrecognized potential source of decisional bias associated with equality judgments.