ABSTRACT Portraits of human faces, from Renaissance artworks to social media selfies, often show a so-called left cheek bias, with the left half of the face put forward more frequently. This is thought to convey emotional expressivity and warmth. A unique scientific resource to determine the temporal continuity of this phenomenon over the last centuries are the portraits of popes, as available on the official Vatican website. Data analysis of the 266 popes did not reveal a significant left cheek bias, with portraits displaying 51% leftward, 3% symmetrical, and 46% rightward bias. When dividing the portraits by every five centuries, the results showed a lack of relationship between posing bias and time period. Descriptive analysis revealed an equal distribution of right and left cheek bias in the earlier centuries, with the last five centuries presenting 60% of leftward bias. Impressively, the last 12 popes (i.e., from 1846 to 2025) had their portraits posed to the left, a phenomenon with a 0.00002% chance of occurring. We suggest that the shift in the roles played by the pope in church and society, mostly in the current and last two centuries, influenced the increased leftward bias observed in recent years.

ABSTRACT Most research into human cognition has focused predominantly on right-handed individuals, ignoring the left-handed minority due to assumed differences in their brain lateralization. Although practical limitations make it challenging to recruit an equal number of left- and right-handed human participants, research into animal models may shed light on the assumed, but rarely tested, associations between motoric handedness, side preference and brain lateralisation. In the present study, we used the family dog, often studied as a model for complex human-analogue socio-cognitive skills. In Study 1, N = 19 dogs completed a range of behavioural tests assessing lateralisation followed by a sleep EEG recording. In Study 2, N = 14 dogs, specifically selected based on prior side bias history in other cognitive experiments, were behaviourally tested in two side-preference tasks and assessed in a sleep EEG measurement. Results show that both negative and positive correlations exist between certain behavioural lateralisation parameters and hemispheric asymmetry in sleep EEG spectrum. These partly support the use-dependent recovery function of sleep (negative correlations) as well as suggest fingerprint-like individual-level associations between sleep and waking behaviour. These findings are relevant for future research capitalizing on the dog as a model for human visuo-spatial attentional biases.

ABSTRACT The role of each hemisphere of the brain in the perception, production and expression of emotions remains a topic of controversy. Based on asymmetries found through neurological and behavioural studies on both human and non-human animals, several hypotheses and theories have been proposed regarding emotional processing. To contribute to this ongoing discussion and get insights on elephant emotional processing, the present study investigates whether the right hemisphere is more activated during negative emotions in Asian elephants (Elephas maximus). Non-invasive behavioural observations using a video-camera were conducted for 70 h on captive individuals. Using all-occurrences sampling, the side of the body (left or right) to which five self-directed behaviours were oriented was performed on each individual. To investigate the relationship between behavioural laterality and emotional valence, post-conflict behavioural sides were compared to baseline ones in three victims of aggression. Results revealed that, after receiving an aggression, the odds of left side-oriented behaviours significantly increased by 1.82 times when compared to baseline levels. These findings suggest a greater involvement of the right hemisphere in negative emotional processing, aligning with previously proposed theories. Overall, this study may contribute to the understanding of emotional processing in elephants and comparative research on brain asymmetry.

ABSTRACT The claim that left handers are over-proportionally common among architects has inspired both scientific theories and popular beliefs about left handedness. However, a review of the existing literature reveals inconsistent findings and a modest overall sample size even when accumulated across studies. The present observational study reinvestigates the notion by assessing the hand preference of acclaimed professional architects. Relevant architects were identified from the winner list of prestigious architecture awards (i.a., The Pritzker prize, The Royal Gold Medal) and by referring to influential architecture magazines. Utilizing pictures and videos available online, hand preference of 515 architects was determined. Of these, 41 cases (8%; confidence limit, CI95%: 5.8–10.5%) were left handed or ambidextrous, a percentage below rather than above the expected 10.6% for the general population (χ² = 3.78, p = .052). To account for known historical trends in left handedness, we selectively considered architects born after 1950. Here, 10.1% (CI95%: 7.0–13.6%) were non-right handed, which was statistically comparable to the expected value (χ² = 0.07, p = .78). In conclusion, the present results allow excluding a relevant over-representation of left and non-right handers among acclaimed architects, challenging the popular belief that left handers (as a group) have a special talent for visual arts and architecture.

ABSTRACT The primate order has received considerable interest in studies on lateralized behaviour due to their hemisphere specialization and potentially major implications for the evolution of the human cerebral cortex. The development of the prefrontal and association regions is required for complex behaviours, and there is evidence that some species show hemispheric specialization in the performance of executive functions. However, laterality in relation to working memory in New World monkeys has received little attention. The main aim of this study was to explore the use of the hands and the tail in spider monkeys (Ateles geoffroyi) while performing two visual-spatial delayed match-to-sample (DMTS) tasks. Eight juvenile male spider monkeys raised in outdoor rain forest enclosures were studied. They were tested on two tasks over a period of 20 days. The first DMTS task had a 15-sec delay and used two different containers to hide a reward. The second had a 60-sec delay and used four different containers. Spider monkeys showed a robust and consistent left-hand preference during both acquisition and execution of DMTS tasks, occasionally accompanied by left-side tail use. The left-hand preference provide evidence for lateralized motor control and contribute to understanding hemispheric specialization to working memory in nonhuman primates.

ABSTRACT Readers must be able to make inferences to maintain coherence during reading. Prior research suggests that the cerebral hemispheres process inferences differently depending on level of textual constraint, however, it is not clear when these hemispheric differences occur during reading. The current study investigates how levels of textual constraint influences the hemispheric processing of bridging inferences. Participants read texts promoting a strongly constrained (Experiment 1) or weakly-constrained (Experiment 2) bridging inference and then performed a lexical decision for targets presented to either the left or right hemisphere. Using event-related potential (ERP) analysis, N400 and P600 waveforms were examined during the target presentation. For strongly constrained inferences, a larger N400 effect was found in the right hemisphere than the left hemisphere. For weakly constrained inferences, there was a larger N400 effect overall, but no differences between the hemispheres. In addition, no hemispheric differences were observed for the P600 waveform between the strongly and weakly constrained inferences. Thus, hemispheric asymmetries seem to occur during the early stages of text processing when readers might generate both strongly and weakly-constrained inferences.

ABSTRACT Pedophilic disorder has been linked to neurodevelopmental differences in diagnosed individuals. One common biomarker for atypical neurodevelopment are elevated levels of atypical handedness as individuals with several neurodevelopmental disorders show increased levels of left-, mixed-, or non-right-hand preference. A few primary studies have indicated that atypical handedness could also be more prevalent in pedophilia and child sexual offenders. However, individual studies are prone to sampling biases. A comprehensive synthesis of the literature on this topic is still missing. In this pre-registered study, we performed a meta-analysis on k = 14 studies that were searched in PubMed, Web of Science, and Google Scholar (until January 2025). These 14 studies measured hand preference in n = 1245 individuals with pedophilia and child sexual offenders and n = 5703 controls. We found evidence against higher rates of atypical handedness irrespective of handedness classification using random-effects frequentist and robust Bayesian meta-analyses. There was no evidence of heterogeneity nor small-study or publication bias across analyses. These results suggest that atypical handedness is not suited to serve as a biomarker for pedophilia.

ABSTRACT This study examined the negative frequency-dependent advantage with a specific focus on half-guard passing in Brazilian jiu-jitsu, a grappling-based martial art that emphasizes ground techniques. We analyzed video footage of Brazilian jiu-jitsu competitions, focusing on half-guard situations, in which guarders (bottom players) entangle one of their opponent’s legs while passers (top players) attempt to disentangle the guard to establish dominant control. Both guarders and passers exhibited lateral preferences: guarders were more likely to entangle their opponent’s right leg, while passers predominantly passed to their left (i.e., the direction opposite to the entangled leg). Moreover, guard passes initiated to the right were more successful in terms of scoring the point (36.70%) compared to those initiated to the left (19.67%). As the attacks to the less common side (i.e., right) were associated with greater success in Brazilian jiu-jitsu competitions, these findings can be taken as evidence for the negative frequency-dependent advantage of lateralized behaviour in real-world combat scenarios.

ABSTRACT One of the trends expected to shape laterality research this decade is closing the gap between human and non-human researchers. A solution to this problem is to view laterality research with a translational lens to leverage knowledge gained in one field to a seemingly disparate field or from one species to another species. The objective of this narrative review was to identify examples of translation in laterality studies that have been conducted in platyrrhine (New World) primates. Our larger goal was to increase rigour and reproducibility for cross-species methodologies in laterality research. As a first step, we surveyed 120 laterality studies conducted in platyrrhine monkeys to describe the research that has been done to date and its impact. In a second step, we conducted a narrative synthesis to identify elements of forward and reverse translation in the reviewed studies on platyrrhine laterality. We described three themes that emerged from our narrative synthesis, and we used these themes to guide our recommendations for future studies in laterality as well as broader health-related research with platyrrhine models.