This experiment was conducted to determine whether perceptual asymmetries would emerge in a task requiring the discrimination of two auditory time intervals. The first interval (standard) was presented binaurally and the other one (comparison) monaurally. The intervals were either filled (continuous sound) or empty (duration between two brief sounds). A total of 24 right-handed participants (12 women, 12 men) completed the four conditions (two Ear×two Structure). The results revealed that filled intervals were perceived as shorter when the monaural signal was presented to the left ear than when it was presented to the right ear, whereas there was no ear effect for empty intervals. Interval structure was not a significant factor when the monaural signals were delivered to the right ear, suggesting a right ear advantage in duration estimation. Finally, temporal sensitivity was better with empty than with filled intervals, but this effect was independent of the location of the monaural signals. The results are discussed with reference to potential effects of attention and the role of structural aspects underlying perceptual asymmetries.

Composition is an important topic in visual art. The literature suggests a bias for objects on the right side (Levy, 1976) and two additional biases with respect to positioning of objects within a rectangular frame: a Centre bias and an Inward bias (Palmer, Gardner, & Wickens, 2008). We analysed images of animals from three datasets of works of art: two datasets were from artists well known for their portraits of animals (Bewick, Stubbs) and the third was a medieval bestiary. There was no overall displacement of the subject to the right or to the left of the picture. However, we found a bias consisting of more space in front compared to behind the animal, consistent with Palmer at al.'s findings and with their definition of an Inward bias. Because our animals never face towards the centre we use the term Anterior bias. In addition, we found a modulation of this bias on the basis of the facing direction of the animal, consisting of a stronger Anterior bias for left-facing animals. This asymmetry may originate from a combination of an Anterior bias and a Right bias. Finally, with respect to size we found that the size of the animals predicted the proportion of the picture occupied, an effect known as “canonical size”.

Research indicates that there are individual differences in the flexibility and ease with which one retrieves and uses concepts stored in memory. Based on prior research suggesting that mixed-handedness is associated with greater cognitive flexibility, it was hypothesised that mixed-handers have access to a relatively diffuse associative network, where link strengths for closely related and distantly related concepts are not as disparate as in the case of strong-handers. This idea was explored using ambiguous words for stimuli, as ambiguous words are known to have both strong (concepts related via dominant meaning) and weak associates (concepts related via subordinate meaning). Consistent with the prediction, mixed-handers showed equal ease in accessing both strongly and weakly related concepts. In Experiment 1 mixed-handers exhibited equivalent priming for dominant and subordinate associates, while strong-handers exhibited priming for dominant associates only. In Experiment 2 ratings of strength of association for dominant versus subordinate associates were examined. Mixed-handedness was associated with lesser disparity of dominant and subordinate association ratings.

Considerable research supports the high frequency of right-handedness in living Homo sapiens, with worldwide rates of approximately nine right- for every one left-hander. Right-handedness appears to be a uniquely human trait, as no other primate species, no matter how proficient in tool use, shows frequencies even close to the strong right bias typical of humans (Cashmore, Uomini, & Chapelain, 2008; McGrew & Marchant 1997; Steele & Uomini, 2009). Here we review our research on human fossils from Sima de los Huesos (Atapuerca, Spain) and their likely descendants, the European Neandertals. We document hand preference in fossils by scratch patterns that occur on the labial (lip) face of incisors and canines, and contend that these patterns provide a reliable means for identifying predominant hand use in these samples. Manipulatory marks on the anterior teeth show a persistent pattern of right-handed actions, implying that the modern human pattern of dominant right-handedness extends deep into the European past.

A large body of work report a leftward bias in face processing. However, it is not clear whether this leftward bias purely reflects the dominance of the right hemisphere or is influenced by scanning habits developed by reading directions. Here, we report two experiments examining how well native readers of right to left Arabic scripts (Egyptians) could match (for identity) a target face that appeared with a companion to a line-up of 10 faces. There was a significant advantage for matching faces that appeared on the left. However, Experiment 2 found that the magnitude of this left face matching bias was almost three times weaker than the magnitude of the leftward bias shown by native readers of left to right English scripts (British). Accordingly, we suggest that the right hemisphere dominance for face processing underlies the leftward face perception bias, but with the interaction of scanning habits.

Schneiderian first rank symptoms (FRS) in schizophrenia have been hypothesised to be secondary to aberrant cerebral lateralisation over the course of human evolution. The ratio of length of second digit to fourth digit (2D:4D) has been put forward as a potential indicator of cerebral lateralisation. This study examined 2D:4D and its asymmetry in antipsychotic-naïve schizophrenia patients (N=79) in comparison with healthy controls (N=75). Psychopathology was assessed using Scales for Assessment of Positive and Negative Symptoms. FRS assessment was performed as per established descriptions. The digit lengths (2D & 4D) were measured using a digital vernier caliper with good inter-rater reliability. Female schizophrenia patients showed significantly lower 2D:4D than female healthy controls. Mean 2D:4D asymmetry index was significantly lower in male schizophrenia patients than male healthy controls. FRS status had significant effect on left 2D:4D as well as 2D:4D asymmetry index, the patients with FRS having the lowest values. Our study findings support association between Schneiderian FRS and low 2D:4D as well as low 2D:4D asymmetry index. Since 2D:4D is linked with limbic asymmetry, our study findings offer further support to the cerebral lateralisation theories of schizophrenia.

Brain asymmetry—i.e. the specialisation of each cerebral hemisphere for sensorimotor processing mechanisms and for specific cognitive functions—is widely distributed among vertebrates. Several factors, such as embryological manipulations, sex, age, and breeds, can influence the maintenance, strength, and direction of laterality within a certain vertebrate species. Brain lateralisation is a universal phenomenon characterising not only cerebral control of cognitive or emotion-related functions but also cerebral regulation of somatic processes, and its evolution is strongly influenced by social selection pressure. Diseases are well known to be a cost of sociality but their role in influencing behaviour has received very little attention. The present study investigates the influence of illness conditions as a source of variation on laterality in a social keystone vertebrate predator model, the lion. In a preliminary stage, the clinical conditions of 24 adult lions were assessed. The same animals were scored for forelimb preference when in the quadrupedal standing position. Lions show a marked forelimb preference with a population bias towards the use of the right forelimb. Illness conditions strongly influenced the strength of laterality bias, with a significant difference between clinically healthy and sick lions. According to these results, health conditions should be recognised as an important source of variation in brain lateralisation.

Among the various interactions between an adult and an infant, postural behaviours and their lateral biases expressed by adults for holding an infant represent a growing field of investigation. To better understand the building up of mother/child relationships, the current study reports data concerning infant-holding biases collected in a new population, namely childcare professionals, where experience with and emotional relationships with infants could be classified as intermediate between basic and advanced. Two sub-populations of childcare professionals were studied: women who work in maternity hospitals and women who work in day-care centres. Their infant-holding side preferences were correlated with emotional perceptive biases to ascertain whether hemispheric specialisation influences holding side biases as well as in basic holding relationships. Results showed that childcare professionals behaved like mothers, which means like participants with advanced holding relationships. The discussion emphasises the complexity of infant-holding behaviours and the importance of considering the nature of holding relationships in the study of side-of-hold biases.

The measurement of tympanic membrane temperature (TMT) using hand-held infrared devices is common in both clinical and experimental research. However, the role that measurement context has on TMT has been overlooked. In the present investigation 94 women and men had their right and left TMT measured by either a male or female investigator. Regardless of participant's gender, when measured by a female investigator the right TMT was significantly lower than the left TMT. When measured by a male investigator, both male and female participants had similar right and left TMT. These lateral TMT results correspond with neuropsychological theories regarding threat appraisal.