Mental rotation does not account for sex differences in left–right confusion

Visual and Verbal Processes in Right-Left Confusion: Psychometric and Experimental Approaches

Errors in discriminating right from left, termed right-left confusion, reflect a failure in translating visuospatial perceptions into verbal representation of right or left (i.e., visuo-verbal process). There may also be verbo-visual process, where verbal cues are translated into visual representations of space. To quantify these two processes underlying right-left confusion, Study 1 investigated the factor structure of the Right-Left Confusability Scale, which assesses daily experiences of right-left confusion. Exploratory factor analysis suggested that these two processes and another factor reflecting mental rotation underlie right-left confusion. Study 2 examined correlations between the (sub)scale scores and performance on orientation judgment tasks reflecting visuo-verbal and verbo-visual processes. Overall, self-reported measures were not associated with the behavioral performances presumably reflecting the two processes. These results suggest that the cognitive mechanisms underlying right-left confusion can be classified into visuo-verbal and verbo-visual processes and mental rotation, although their psychometric and behavioral indices might be distinct. Further studies may develop better assessments of right-left confusion reflecting these processes.

Distinguishing left from right: A large-scale investigation of left-right confusion in healthy individuals

The ability to distinguish left from right has been shown to vary substantially within healthy individuals, yet its characteristics and mechanisms are poorly understood. In three experiments, we focused on a detailed description of the ability to distinguish left from right and the role of individual differences, and further explored the potential underlying mechanisms. In Experiment 1, a questionnaire concerning self-reported left-right identification (LRI) and strategy use was administered. Objective assessment was used in Experiment 2 by means of vocal responses to line drawings of a figure, with the participants' hands in a spatially neutral position. In Experiment 3, the arm positions and visibility of the hands were manipulated to assess whether bodily posture influences left-right decisions. Results indicate that 14.6% of the general population reported insufficient LRI and that 42.9% of individuals use a hand-related strategy. Furthermore, we found that spatial alignment of the participants' arms with the stimuli increased performance, in particular with a hand-related strategy and females. Performance was affected only by the layout of the stimuli, not by the position of the participant during the experiment. Taken together, confusion about left and right occurs within healthy population to a limited extent, and a hand-related strategy affects LRI. Moreover, the process involved appears to make use of a stored body representation and not bottom-up sensory input. Therefore, we suggest a top-down body representation is the key mechanism in determining left and right, even when this is not explicitly part of the task.

'What … you can't tell left from right?' Medical students' experiences in making laterality decisions

CONTEXT

Wrong-sided procedures represent some of the most catastrophic errors in health care. Although errors in laterality are multifaceted in origin, human error is considered to be an important root cause. Evidence suggests that a significant proportion of the population, including medical students, experience difficulty in left-right discrimination (LRD). Given that not all medical students have equal LRD ability, there have been calls to raise awareness of this issue in medical education. The experiences of medical students with LRD, including those who have difficulty, remain unknown.

OBJECTIVES

This study was designed to gain deep insights into the lived experiences of medical students in LRD.

METHODS

A qualitative study was conducted using hermeneutic phenomenology. Medical students with a wide range of abilities in LRD were invited to participate and to be interviewed. Interviews were transcribed and analysed using template analysis to generate research themes. Members of the research team were continually reflexive when remaining firmly rooted in the data and in the principles of the hermeneutic process.

RESULTS

Analysis yielded four main themes: (i) discriminating right from left: an unconscious or a conscious task? (ii) 'What … you can't tell right from left?': an undesirable skill deficit; (iii) concealment, and (iv) 'But you're going to be a doctor!': impact on professional identity formation.

CONCLUSIONS

This study challenges normative expectations that LRD is an effortless task for all. Individuals who are challenged in LRD must engage in a complex conscious process to determine right from left. For the most part, this process is relatively effortless. However, the context of being a medical student can impose extra demands and heightens the risk associated with potential error. Medical education needs to respond by raising the profile of this challenge, with which many of our medical students are confronted, and by extending support to assist them in the interests of safe patient care.

The Impact of Handedness, Sex, and Cognitive Abilities on Left-Right Discrimination: A Behavioral Study

The present study examined the relationship between left–right discrimination (LRD) performance and handedness, sex and cognitive abilities. In total, 31 men and 35 women – with a balanced ratio of left-and right-handers – completed the Bergen Left–Right Discrimination Test. We found an advantage of left-handers in both identifying left hands and in verifying “left” propositions. A sex effect was also found, as women had an overall higher error rate than men, and increasing difficulty impacted their reaction time more than it did for men. Moreover, sex interacted with handedness and manual preference strength. A negative correlation of LRD reaction time with visuo-spatial and verbal long-term memory was found independently of sex, providing new insights into the relationship between cognitive skills and performance on LRD.

'Sorry, I meant the patient's left side': impact of distraction on left-right discrimination

CONTEXT

Medical students can have difficulty in distinguishing left from right. Many infamous medical errors have occurred when a procedure has been performed on the wrong side, such as in the removal of the wrong kidney. Clinicians encounter many distractions during their work. There is limited information on how these affect performance.

OBJECTIVES

Using a neuropsychological paradigm, we aim to elucidate the impacts of different types of distraction on left-right (LR) discrimination ability.

METHODS

Medical students were recruited to a study with four arms: (i) control arm (no distraction); (ii) auditory distraction arm (continuous ambient ward noise); (iii) cognitive distraction arm (interruptions with clinical cognitive tasks), and (iv) auditory and cognitive distraction arm. Participants' LR discrimination ability was measured using the validated Bergen Left-Right Discrimination Test (BLRDT). Multivariate analysis of variance was used to analyse the impacts of the different forms of distraction on participants' performance on the BLRDT. Additional analyses looked at effects of demographics on performance and correlated participants' self-perceived LR discrimination ability and their actual performance.

RESULTS

A total of 234 students were recruited. Cognitive distraction had a greater negative impact on BLRDT performance than auditory distraction. Combined auditory and cognitive distraction had a negative impact on performance, but only in the most difficult LR task was this negative impact found to be significantly greater than that of cognitive distraction alone. There was a significant medium-sized correlation between perceived LR discrimination ability and actual overall BLRDT performance.

CONCLUSIONS

Distraction has a significant impact on performance and multifaceted approaches are required to reduce LR errors. Educationally, greater emphasis on the linking of theory and clinical application is required to support patient safety and human factor training in medical school curricula. Distraction has the potential to impair an individual's ability to make accurate LR decisions and students should be trained from undergraduate level to be mindful of this.

The neural correlates of sex differences in left-right confusion

Difficulties in left-right discrimination (LRD) are commonly experienced in everyday life situations. Here we investigate the neurocognitive mechanisms of LRD and the specific role of left angular gyrus. Given that previous behavioral research reported women to be more susceptible to left-right confusion, the current study focuses particularly on the neural basis of sex differences in LRD while controlling for potential menstrual cycle effects (repeated measures design). 16 women and 15 men were presented pictures of pointing hands in various orientations (rotated versus non-rotated) and were asked to identify them as left or right hands. Results revealed that LRD was particularly associated with activation in inferior parietal regions, extending into the right angular gyrus. Irrespective of menstrual cycle phase, women, relative to men, recruited more prefrontal areas, suggesting higher top-down control in LRD. For the subset of rotated stimuli as compared to the non-rotated, we found leftward asymmetry for both men and women, although women scored significantly lower. We conclude that there are sex differences in the neurocognitive mechanisms underlying LRD. Although the angular gyrus is involved in LRD, several other parietal areas are at least as critical. Moreover, the hypothesis that more left-right confusion is due to more bilateral activation (in women) can be rejected.

Sex hormones and mental rotation: an intensive longitudinal investigation

The present study used an intensive longitudinal design to examine whether mental rotation performance varies according to a monthly cycle in both males and females and whether these variations are related to variations in progesterone, estradiol, and testosterone levels. We collected reaction time and accuracy data for 10 males and seven females each workday over eight weeks using 136 pairs of mental rotation stimuli/day, and measured sexual hormones concentrations in the saliva twice a week. A mixed linear model statistical analysis revealed that all females and seven males showed significant cycle effects in mental rotation performance. The female cycle showed an amplitude that was twice as large compared with the amplitude found in males. For males and females, estradiol and testosterone were significantly linearly and quadratically related to interindividual variation in performance at the beginning of the study (progesterone was linearly related to performance for females). The association between testosterone and performance differed across sexes: for males, it had an inverse U-shape, for females it was U-shaped. Towards the end of the study, none of the hormones were significantly related to performance anymore. Thus, the relationship between hormones and mental rotation performance disappeared with repeated testing. Only estradiol levels were significantly elevated at the lowest point of the cycle in mental rotation performance in females. In conclusion, in this intensive longitudinal study spanning two months, a monthly cycle in mental rotation performance was found among both males and females, with a larger cycle's amplitude for females.

Sex differences in language asymmetry are age-dependent and small: a large-scale, consonant-vowel dichotic listening study with behavioral and fMRI data

Men are often believed to have a functionally more asymmetrical brain organization than women, but the empirical evidence for sex differences in lateralization is unclear to date. Over the years we have collected data from a vast number of participants using the same consonant-vowel dichotic listening task, a reliable marker for language lateralization. One dataset comprised behavioral data from 1782 participants (885 females, 125 non-right-handers), who were divided in four age groups (children <10 yrs, adolescents = 10-15 yrs, younger adults = 16-49 yrs, and older adults >50 yrs). In addition, we had behavioral and functional imaging (fMRI) data from another 104 younger adults (49 females, aged 18-45 yrs), who completed the same dichotic listening task in a 3T scanner. This database allowed us to comprehensively test whether there is a sex difference in functional language lateralization. Across all participants and in both datasets a right ear advantage (REA) emerged, reflecting left-hemispheric language lateralization. Accordingly, the fMRI data revealed a leftward asymmetry in superior temporal lobe language processing areas. In the N = 1782 dataset no main effect of sex but a significant sex by age interaction emerged: the REA increased with age in both sexes but as a result of an earlier onset in females the REA was stronger in female than male adolescents. In turn, male younger adults showed greater asymmetry than female younger adults (accounting for <1% of variance). There were no sex differences in children and older adults. The males in the fMRI dataset (N = 104) also had a greater REA than females (accounting for 4% of variance), but no sex difference emerged in the neuroimaging data. Handedness did not affect these findings. Taken together, our findings suggest that sex differences in language lateralization as assessed with dichotic listening exist, but they are (a) not necessarily reflected in fMRI data, (b) age-dependent and (c) relatively small.

Sex differences in components of imagined perspective transformation

Little research to date has examined whether sex differences in spatial ability extend to the mental self rotation involved in taking on a third party perspective. This question was addressed in the present study by assessing components of imagined perspective transformations in twenty men and twenty women. Participants made speeded left-right judgements about the hand in which an object was held by front- and back- facing schematic human figures in an "own body transformation task." Response times were longer when the figure did not share the same spatial orientation as the participant, and were substantially longer than those made for a control task requiring left-right judgements about the same stimuli from the participant's own point of view. A sex difference in imagined perspective transformation favouring males was found to be restricted to the speed of imagined self rotation, and was not observed for components indexing readiness to take a third party point of view, nor in left-right confusion. These findings indicate that the range of spatial abilities for which a sex difference has been established should be extended to include imagined perspective transformations. They also suggest that imagined perspective transformations may not draw upon those empathic social-emotional perspective taking processes for which females show an advantage.

Dichotic listening and left-right confusion

The present study examined the relationship between individual differences in dichotic listening (DL) and the susceptibility to left-right confusion (LRC). Thirty-six men and 59 women completed a consonant-vowel DL test, a behavioral LRC task, and an LRC self-rating questionnaire. Significant negative correlations between overall DL accuracy and LRC rates in men (behavioral task) and self-ratings in women, indicated that the more participants struggled with left-right discrimination, the fewer DL syllables they reported correctly. However, there was no relationship between LRC and the typical right ear advantage. Thus, there is a sex- and task-dependent relationship between LRC and overall DL accuracy, but not between LRC and ear asymmetry. It is concluded that (a) atypical ear asymmetries, as in certain clinical populations, cannot be explained by associated deficits in left-right discrimination, and (b) LRC can negatively affect task performance, even when participants do not have to make explicit "left" versus "right" decisions.