Effect of Culturally Mediated Right-Favoritism on the Direction of Pseudoneglect on Line Bisection Tasks

Objectives: Arabs have a right-to-left language and engage in favoring of the right side or limb when implementing daily routine practices. The purpose of this research is to explore the effect this cultural attitude might have on pseudoneglect, by comparing with a southeast Asian sample that has a left-to-right language structure.Methods: Participants were from two separate ethnic groups (Arabs and Filipinos), residing in Saudi Arabia, healthy individals 18 years and above were allowed to volunteer in the study. The participants were recruited at King Saud University Medical City and the general community by both convenience and snowball sampling. Social demographic information such as gender, age, years of education, dominant hand, was also documented. The line bisection task (LBT) contained 36 randomly assorted lines of three different lengths placed at five different locations on a white sheet. The percent deviation score (PDS) was used to quantify pseudo-neglect. Tests of statistical significance including t-tests and mixed-effects regression were performed to determine if differences existed among different demographic variables or among line properties, respectively.Results: A total of 256 were enrolled (Arabs 52.3%). The overall PDS mean and standard deviation (SD) was −0.64 (2.87), p = 0.0004, which shows a significant leftward deviation in the entire cohort. PDS was −1.26 (2.68) in Filipinos, and −0.08 (2.94) in Arabs. The difference was statically significant (p < 0.0001). Mixed effects model showed positive changes in the PDS value as the length of the line increased (p < 0.0001) and as the line was more rightward placed (p < 0.0001). However, Filipino participants would still exhibit negative changes in the PDS value in comparison to Arabs (p < 0.0001); There were no significant associations between PDS and other factors such as age, years of education and gender.Conclusion: Differences found here between two distinct ethnic groups support the hypothesis that certain cultural aspects such as language direction and other cultural practices influence direction and degree of pseudo-neglect.

Spatial asymmetries (“pseudoneglect”) in free visual exploration—modulation of age and relationship to line bisection

When humans visually explore an image, they typically tend to start exploring its left side. This phenomenon, so-called pseudoneglect, is well known, but its time-course has only sparsely been studied. Furthermore, it is unclear whether age influences pseudoneglect, and the relationship between visuo-spatial attentional asymmetries in a free visual exploration task and a classical line bisection task has not been established. To address these questions, 60 healthy participants, aged between 22 and 86, were assessed by means of a free visual exploration task with a series of naturalistic, colour photographs of everyday scenes, while their gaze was recorded by means of a contact-free eye-tracking system. Furthermore, a classical line bisection task was administered, and information concerning handedness and subjective alertness during the experiment was obtained. The results revealed a time-sensitive window during visual exploration, between 260 and 960 ms, in which age was a significant predictor of the leftward bias in gaze position, i.e., of pseudoneglect. Moreover, pseudoneglect as assessed by the line bisection task correlated with the average gaze position throughout a time-window of 300–1490 ms during the visual exploration task. These results suggest that age influences visual exploration and pseudoneglect in a time-sensitive fashion, and that the degree of pseudoneglect in the line bisection task correlates with the average gaze position during visual exploration in a time-sensitive manner.

A meta-analysis of line bisection and landmark task performance in children

Young adults exhibit a subtle, group-level asymmetry of lateral spatial attention favouring the left hemispace over the right (pseudoneglect). We have recently shown that leftward biases are maintained in older adults aged ≥50 when measured using the line bisection task (Learmonth and Papadatou-Pastou 2021). Here we present a meta-analysis of spatial biases in children aged ≤16 years. Databases (PsycINFO, Web of Science, and Scopus) and pre-print servers (bioRxiv, medRxiv, and PsyArXiv) were searched up to 8th March 2021 for studies involving children aged ≤16, who were tested using the line bisection or landmark task, and who had not been recruited as an atypically developing group. Thirty-six datasets from 33 studies, involving 2515 children, were included. A small leftward bias was identified overall (Cohen’s d = -.18, 95% CI = -.36, -.01). No spatial bias was identified when the 33 line bisection studies were analysed separately (d = -.16, 95% CI = -.35, .04). Moderator analysis of the line bisection task found a strong influence of the hand that was used to bisect the line, with right-handed actions resulting in right-biased bisections, and left-handed actions in left-biased bisections (symmetrical neglect). Bisections were slightly more leftward in studies that included a higher percentage of boys relative to girls. Age, hand preference, and the control group status of the children did not moderate spatial biases and we found no evidence of small study publication bias. However, the number of studies included in each moderator analysis was small. This meta-analysis confirms that pseudoneglect is present in children, but its detection is dependent on the task that is used.

A Meta-Analysis of Line Bisection and Landmark Task Performance in Older Adults

Young adults exhibit a small asymmetry of visuospatial attention that favours the left side of space relative to the right (pseudoneglect). However, it remains unclear whether this leftward bias is maintained, eliminated or shifted rightward in older age. Here we present two meta-analyses that aimed to identify whether adults aged ≥50 years old display a group-level spatial attention bias, as indexed by the line bisection and the landmark tasks. A total of 69 datasets from 65 studies, involving 1654 participants, were analysed. In the meta-analysis of the line bisection task (n = 63), no bias was identified for studies where the mean age was ≥50, but there was a clear leftward bias in a subset where all individual participants were aged ≥50. There was no moderating effect of the participant’s age or sex, line length, line position, nor the presence of left or right cues. There was a small publication bias in favour of reporting rightward biases. Of note, biases were slightly more leftward in studies where participants had been recruited as part of a stand-alone older group, compared to studies where participants were recruited as controls for a clinical study. Similarly, no spatial bias was observed in the meta-analysis of the landmark task, although the number of studies included was small (n = 6). Overall, these results indicate that over 50s maintain a group-level leftward bias on the line bisection task, but more studies are needed to determine whether this bias can be modulated by stimulus- or state-dependent factors.

No Evidence of Perceptual Pseudoneglect in Alexithymia

Neuroscience research links alexithymia, the difficulty in identifying and describing feelings and emotions, with left hemisphere dominance and/or right hemisphere deficit. To provide behavioral evidence for this neuroscientific hypothesis, we explored the relationship between alexithymia and performance in a line bisection task, a standard method for evaluating visuospatial processing in relation to right hemisphere functioning. We enrolled 222 healthy participants who completed a version of the 20-item Toronto Alexithymia Scale (TAS-20), which measures alexithymia, and were asked to mark (bisect) the center of a 10-cm horizontal segment. The results document a significant rightward shift in the center of the line in participants with borderline and manifest alexithymia compared with non-alexithymic individuals. The higher the TAS-20 score, the greater the rightward shift in the line bisection task. This finding supports the right hemisphere deficit hypothesis in alexithymia and suggests that visuospatial abnormalities may be an important component of this mental condition.

No Evidence of Perceptual Pseudoneglect in Alexithymia

The research in neuroscience links alexithymia, the difficulty of identifying and describing feelings and emotions, with a left hemisphere preference and/or a right hemisphere deficit. To provide a neuropsychological support to this finding, we explored the relationship between alexithymia and the performance in a line bisection task, a standard method to evaluate spatial attention in relation with the functioning of the right hemisphere. 222 healthy participants completed a version of the TAS-20 scale, which measures alexithymia, and were asked to mark (bisect) the center of a 10 cm horizontal segment. The results document a significant rightward shift of the line center in borderline and manifest alexithymic participants, as compared to non-alexithymic individuals. Moreover, the higher the TAS-20 score the greater the rightward shift in the line bisection task. This result supports the right-hemisphere deficit hypothesis in alexithymia and suggests that visuospatial abnormalities may be an inner component of their profile.

A meta-analysis of line bisection and landmark task performance in older adults

Young adults exhibit a small asymmetry of visuospatial attention that favours the left side of space relative to the right (pseudoneglect). However, it remains unclear whether this leftward bias is maintained, eliminated or shifted rightward in older age. Here we present two meta-analyses that aimed to identify whether adults aged ≥50 years old display a group-level spatial attention bias, as indexed by the line bisection and the landmark tasks. A total of 69 datasets from 65 studies, involving 1654 participants, were analysed. In the meta-analysis of the line bisection task (n = 63), no bias was identified for studies where the mean age was ≥50, but there was a clear leftward bias in a subset where all individual participants were aged ≥50. There was no moderating effect of the participant’s age or sex, line length, line position, nor the presence of left or right cues. There was a small publication bias in favour of reporting rightward biases. Of note, biases were slightly more leftward in studies where participants had been recruited as part of a stand-alone older group, compared to studies where participants were recruited as controls for a clinical study. Similarly, no spatial bias was observed in the meta-analysis of the landmark task, although the number of studies included was small (n = 6). Overall, these results indicate that over 50s maintain a group-level leftward bias on the line bisection task, but more studies are needed to determine whether this bias can be modulated by stimulus- and/or state-dependent factors.