Pair bonding and lateral neck-resting preferences in captive Caribbean flamingos (Phoenicopterus ruber)

When flamingos rest, they typically lay their head on their back and curve their neck to either the right or left of their body, with both individual and population-level lateral preferences for rightward neck resting when preferences are tracked over time (Anderson, Williams, & O'Brien, 2009). The present study attempted to replicate these previous neck-resting preferences, to examine how they changed over time, and to examine the possibility of a relationship between lateral neck-resting preference and pair bonding in captive Caribbean flamingos (Phoenicopterus ruber) housed at the Philadelphia Zoo (Philadelphia, PA, USA). Results successfully replicated the individual- and population-level lateral preferences for rightward neck resting, and demonstrated that these preferences were stable over time. Moreover, individual flamingos that demonstrated stronger pair bond strengths tended to differ less from their partners in terms of neck-resting preference than did those birds displaying weaker pair bond strengths, suggesting a relationship between laterality and social cohesion.     

Lateral asymmetry in the freely occurring behaviour of budgerigars (Melopsittacus undulatus) and its relation to cognitive performance

Hemispheric laterality and its provision of potential fitness advantages to aves is a widespread topic of research in budgerigars and other parrot species [e.g., Magat, M. & Brown, C. (2009). Laterality enhances cognition in Australian parrots. Proceedings of the Royal Society B: Biological Sciences, 276, 4155–4162]. In the current study, lateral preferences were tracked for 11 captive-reared budgerigars that subsequently underwent 2 cognitive problem-solving tests: a tool-use problem and a dig-discrimination task. Two significant individual-level lateral preferences (a leftward unipedal support preference and a rightward preening side preference) and 1 significant population-level preference (a right-side preening preference) were obtained. Lateral preening side preference indices for individual subjects correlated with various measures of performance on the dig task, such that right-side preening preferences and stronger lateral preferences irrespective of direction were associated with enhanced dig task performance. The data generally support the idea that laterality in aves serves as a good predictor of increased cognitive capability, while also offering new evidence for population-level lateral preferences in the species.     

Individual differences in the preferred neck-resting position of Caribbean flamingos (Phoenicopterus ruber)

When resting, flamingos often lay their heads along their backs. While in this position they must curve their necks to either the right or left of their midline. Observations of captive Caribbean flamingos at the Philadelphia Zoo (Philadelphia, PA, USA) were conducted in order to determine if individual birds would display consistent preferences in neck-resting position over multiple observations. While individual birds were shown to vary greatly in regards to the strength and direction of their preferences, a significant flock-level preference towards neck resting to the right was obtained. Analysis of individual flamingos revealed that 5 out of 17 birds displayed preferences that significantly differed from chance, with each of these birds preferring to rest their necks to the right. From the present data we can conclude that flamingos display behavioural laterality of neck-resting position at both the level of the group and that of the individual.     

Individual differences in the preferred neck-resting position of Caribbean flamingos (Phoenicopterus ruber)

When resting, flamingos often lay their heads along their backs. While in this position they must curve their necks to either the right or left of their midline. Observations of captive Caribbean flamingos at the Philadelphia Zoo (Philadelphia, PA, USA) were conducted in order to determine if individual birds would display consistent preferences in neck-resting position over multiple observations. While individual birds were shown to vary greatly in regards to the strength and direction of their preferences, a significant flock-level preference towards neck resting to the right was obtained. Analysis of individual flamingos revealed that 5 out of 17 birds displayed preferences that significantly differed from chance, with each of these birds preferring to rest their necks to the right. From the present data we can conclude that flamingos display behavioural laterality of neck-resting position at both the level of the group and that of the individual.     

Lateral organisation in nineteenth-century studio photographs is influenced by the direction of writing: A comparison of Iranian and Spanish photographs

The direction of reading has been found to have a significant effect upon aesthetic preference, with left-to-right readers showing a preference for stimuli with a rightward directionality while right-to-left readers prefer stimuli with a leftward directionality. This study looks at a large set of posed, studio photographs to study the cultural interaction between direction of reading and lateral organisation, comparing a corpus of 735 nineteenth-century photographs from Iran (right-to-left reading) with a similar corpus of 898 photographs from Spain (left-to-right readers). Five separate types of composition were studied: linear ordering, usually by height; couples; individuals posing by a chair; individuals posing by a table; and portraits. Lateral preferences were found for all five types of photograph, with the lateral organisation of Iranian photographs being the reverse of that in the Spanish photographs. These data provide support for the influence of direction of reading upon aesthetic organisation in naturalistically produced photographs.     

Fly on the right: Lateral preferences when choosing aircraft seats

A small preference has been observed for people to choose seats on the left of aircraft when booking via an online system. Although this is consistent with pseudoneglect—the known leftward bias in perception and representation—rightward preferences have been commonly observed in seating selection tasks in other environments. Additionally, the previous research in aircraft seating was unable to dissociate a bias to one side of the screen from a bias to one side of the cabin of the aircraft. Here, we present a study in which participants were asked to select seats for a range of fictional flights. They demonstrated a preference for seats on the right of the cabin, irrespective of whether the right of the cabin appeared to either the right or the left of the screen, a preference for seats towards the front of the aircraft and a preference to favour window and aisle seats. This suggests, in contrast to previous research, that participants demonstrated a rightward lateral bias to representations of an aircraft. These results may have implications for our understanding of asymmetries in cognition as well as having potentially important practical implications for airlines.     

Orientation of the stethoscope around the neck: a random phenomenon or an indicator of cerebral lateralisation? Cross-sectional survey

This study aimed to determine whether the orientation of the stethoscope when placed around the neck by physicians is a random occurrence or if this represents a lateral preference. A cross-sectional questionnaire survey was conducted, recruiting 186 medical doctors of all grades from the University Hospital of Wales, Cardiff. Stethoscope orientation preference, and seven other measures of lateral preference (handedness, footedness, eyedness, earedness, hand clasping, arm folding, and leg crossing), were assessed. The percentage of right-type, left-type, and indifferent-type orientation for each of the eight lateral preferences was determined, and 60%, 35%, and 5% of participants demonstrated right, left, and indifferent stethoscope orientation types, respectively. Stethoscope orientation preference correlated with handedness, footedness, earedness, and hand-clasping, but not with eyedness, arm-folding, or leg-crossing. Stethoscope orientation preference is not a chance phenomenon and may be an expression of cerebral dominance.     

Birth order and lateral preferences

Associations between birth order and lateral preferences of hand, eye and foot were examined in a sample of 6436 black seven year old boys and girls whose mothers participated in the Collaborative Perinatal Project (CPP) in Philadelphia. Overall, most of the subjects (87%) showed right hand preference, and the majority of subjects showed right eye (55%) and foot (63%) preferences. Analysis of cross preferences indicated some tendency for a consistent right side orientation. However, patterns of lateral preferences were similar for both boys and girls across seven birth order groups. The data were interpreted as showing that birth order and lateral preferences are not interrelated.     

The “consonance effect” and the hemispheres: A study on a split-brain patient

The present study investigated the consistency of the head-turning bias in kissing. In particular we addressed what happens if a person who prefers to kiss with the head turned to the right kisses a person who prefers to kiss with the head turned to the left. To this end, participants (N=57) were required to kiss a life-sized doll's head rotated in different orientations that were either compatible or incompatible with the participants’ head-turning preference. Additionally, participants handedness, footedness, and eye preference was assessed. Results showed that a higher percentage of participants preferred to kiss with their head turned to the right than to the left. In addition, the right-turners were more consistent in their kissing behaviour than left-turners. That is, with the doll's head rotated in an incompatible direction, right-turners were less likely to switch their head to their non-preferred side. Since no clear relationships between head-turning bias and the other lateral preferences (i.e., handedness, footedness, and eye preference) were discerned, the more consistent head-turning bias among right-turners could not be explained as deriving from a joint pattern of lateral preferences that is stronger among individuals with rightward as compared to individuals with leftward lateral preferences.     

Birth stress and lateral preferences

Conflicting evidence exists concerning the possible role of birth stress in the etiology of left-sided lateral preferences. In order to clarify this issue, associations among lateral preferences of hand, eye, and foot and eight indices of prenatal and perinatal stress were examined in the present study on a sample of 987 boys and girls who participated in the Philadelphia Collaborative Perinatal Project. Controls were instituted for some of the methodological and measurement problems encountered in past birth stress and laterality research. Results showed that subjects with different lateral preferences did not differ significantly in their distributions of all but one birth stress items. Hence, there was no substantial evidence for a link between birth stress and left-sided preferences. Alternative hypotheses for the etiology of left-sidedness should therefore be explored.     

Lateral preference patterns as possible correlates of successfully switched left hand writing: Data and a theory

Left-handers often have had to contend with pressure to switch their preferred writing hand and shift attempt reports are common, especially among older adult left-handers. Three groups of left-handers can be defined by combining two variables, writing hand side and the report of a rightward hand preference shift attempt. The three groups are, first, right hand writers who report a rightward shift (successfully shifted left-handers); second, left hand writers who report a rightward shift attempt (unsuccessfully shifted left-handers); and, finally, left hand writers who do not report a rightward shift attempt. The underlying mechanisms that determine the success or failure of a handwriting shift attempt remain unclear. The present study examined the history of attempts to switch the preferred writing hand in a sample of 1277 adults aged 65 to 100 years of age. Older adults are well suited to participate in such a study because pressure to switch hand preference was especially severe for those who grew up in the early part of the 20th century; reports of rightward shift attempts are more common in this age group than among younger adults. Our results suggest that the three groups of left-handers, distinguished by the presence or absence of a shift history report and writing hand side, can also be distinguished from each other on the basis of their overall lateral preference profiles (the sides of hand, foot, eye, and ear preferences). Left hand writers, with and without reports of a rightward shift history, showed stronger left side lateralisation patterns when compared to right hand writers who reported a rightward switch (the successfully shifted left-handers).     

Lateral preference patterns as possible correlates of successfully switched left hand writing: data and a theory

Left-handers often have had to contend with pressure to switch their preferred writing hand and shift attempt reports are common, especially among older adult left-handers. Three groups of left-handers can be defined by combining two variables, writing hand side and the report of a rightward hand preference shift attempt. The three groups are, first, right hand writers who report a rightward shift (successfully shifted left-handers); second, left hand writers who report a rightward shift attempt (unsuccessfully shifted left-handers); and, finally, left hand writers who do not report a rightward shift attempt. The underlying mechanisms that determine the success or failure of a handwriting shift attempt remain unclear. The present study examined the history of attempts to switch the preferred writing hand in a sample of 1277 adults aged 65 to 100 years of age. Older adults are well suited to participate in such a study because pressure to switch hand preference was especially severe for those who grew up in the early part of the 20th century; reports of rightward shift attempts are more common in this age group than among younger adults. Our results suggest that the three groups of left-handers, distinguished by the presence or absence of a shift history report and writing hand side, can also be distinguished from each other on the basis of their overall lateral preference profiles (the sides of hand, foot, eye, and ear preferences). Left hand writers, with and without reports of a rightward shift history, showed stronger left side lateralisation patterns when compared to right hand writers who reported a rightward switch (the successfully shifted left-handers).     

Lateralized preferences and right-left discrimination in the monkey: choice of mirror-image shape, position of recovered food and hand usage.

Rhesus monkeys were tested for lateral preferences during mirror-image shape discrimination and food recovery from a row of pellets. Position of recovered food was unrelated to hand preference or mirror-image preference. There was no significant difference in the number of individuals preferring right and left lateral mirror-image shapes. Individuals tended to retain the same mirror-image preference to the same degree upon repeated testing. Animals of greater weight had stronger preferences. In all these respects, the features of mirror-image preference resembled those previously described for hand preference during a simple reaching task. The strength of different lateral preferences expressed by each animal were not significantly related thus failing to support the concept that asymmetric bodily responses can serve as cues for right-left discrimination in the environment. However, when the direction as well as strength of preference was considered, there appeared to be a tendency for animals to prefer the mirror-image shape whose reward bias was opposite to that of the preferred hand. This finding might have been due to a positional bias though there was evidence against this possibility.     

Hand preference in patients with allergy,juvenile cancer,and schizophrenia

Patients with allergy (n = 50), juvenile cancer (n = 50), and schizophrenia (n = 37), and nonpatient controls (n = 200) were asked to indicate their hand preferences on a 7‐point scale (1 = left always, 7 = right always) for the 32‐item Waterloo Handedness Questionnaire. Except for patients with schizophrenia, who exhibited a higher incidence of mixed hand preference, groups showed a clear rightward bias. Further analyses suggested that mixed hand preference in schizophrenia was evident more often for unskilled than skilled hand activities.     

Lateral preference and verbal skills: a survey in school settings

The relation among hand, foot and eye lateral preference indices and certain verbal ability tests was studied in a group of 497 elementary school children. According to the performance on the verbal ability tests, the original sample was divided into a Lower and an Upper Group, and percentages of left preferences, consistent right and left preferences, crossed hand-foot, hand-eye, foot-eye preferences and congruent preferences were compared. The only comparison that proved to be significant was the evidence of a lower left preference percentage in reading speed in the Upper Group as compared to the Lower Group. A similar series of comparisons between a subgroup (N = 14) of children with serious reading problems and the group as a whole, did not lead to significant results. We therefore conclude that at least for subjects regularly attending school, there is no relation among lateral preference and the above mentioned verbal skills.     

Hand preference in patients with allergy, juvenile cancer, and schizophrenia

Patients with allergy (n = 50), juvenile cancer (n = 50), and schizophrenia (n = 37), and nonpatient controls (n = 200) were asked to indicate their hand preferences on a 7-point scale (1 = left always, 7 = right always) for the 32-item Waterloo Handedness Questionnaire. Except for patients with schizophrenia, who exhibited a higher incidence of mixed hand preference, groups showed a clear rightward bias. Further analyses suggested that mixed hand preference in schizophrenia was evident more often for unskilled than skilled hand activities.     

Animal lateralization and social recognition: quails use their left visual hemifield when approaching a companion and their right visual hemifield when approaching a stranger

Quails were tested for leftward and rightward turning preferences in a detour task. When facing a mirror located behind a barrier composed of vertical bars, quails showed a striking population-level preference for turning leftward. In order to check whether the asymmetry reflected a motor or a sensory (i.e. visual hemifield) bias, in a second experiment quails were reared in pairs and then tested in the detour task with a familiar (companion) or an unfamiliar (stranger) conspecific as a target. Quails turned leftward when viewing the stranger, but they turned rightward when viewing the companion. These findings are discussed in relation to current evidence for brain lateralization in response to social stimuli in non-human animals.     

Lateral preferences and their assessment in school-aged children

A behaviour-based lateral preference instrument (the Lateral Preferences Questionnaire; LPQ; Van Strien, 1992, 2001) was administered to a large sample of school-aged children. The aims of the present study were twofold: (i) to evaluate the factor structure and the psychometric properties of the LPQ, and (ii) to evaluate the effects of age, gender, and mean level of parental education on lateral preferences and lateral consistency. Two factor models had an excellent fit with the data. In the first model the LPQ items were considered to be indicators of four different lateral preference factors (the hand, foot, eye, and ear preference factors). In the second model the LPQ items were considered to be indicators of four lateral preference factors, which were in turn expected to load on a single underlying general lateral preference factor. The psychometric properties of the derived hand and eye preference scales of the LPQ were good to excellent, and the psychometric properties of the foot and ear preference scales were acceptable. Lateral preferences and lateral consistency were not affected by age, gender, or mean level of parental education.     

Description and Validation of a Flexible and Broadly Usable Handedness Questionnaire

Empirical evidence is provided which shows that handedness questionnaires should: (a) comprise items that cover skilled and unskilled activities; (b) be sufficiently long to capture a “mass effect” of variability in lateral preferences over a range of items; and (c) allow graded answer options for individual items rather than forced left/right choices. When using questionnaires that meet these criteria, it is possible to establish significant correlations between hand preference and performance even within a group of righthanders. In addition, such questionnaires are flexible enough to accommodate a great variety of handedness classification schemes.     

Description and validation of a flexible and broadly usable handedness questionnaire

Empirical evidence is provided which shows that handedness questionnaires should: (a) comprise items that cover skilled and unskilled activities; (b) be sufficiently long to capture a 'mass effect' of variability in lateral preferences over a range of items; and (c) allow graded answer options for individual items rather than forced left/right choices. When using questionnaires that meet these criteria, it is possible to establish significant correlations between hand preference and performance even within a group of right-handers. In addition, such questionnaires are flexible enough to accommodate a great variety of handedness classification schemes.