Laterality and Flight: Concurrent Tests of Side-Bias and Optimality in Flying Tree Swallows

Behavioural side-bias occurs in many vertebrates, including birds as a result of hemispheric specialization and can be advantageous by improving response times to sudden stimuli and efficiency in multi-tasking. However, behavioural side-bias can lead to morphological asymmetries resulting in reduced performance for specific activities. For flying animals, wing asymmetry is particularly costly and it is unclear if behavioural side-biases will be expressed in flight; the benefits of quick response time afforded by side-biases must be balanced against the costs of less efficient flight due to the morphological asymmetry side-biases may incur. Thus, competing constraints could lead to context-dependent expression or suppression of side-bias in flight. In repeated flight trials through an outdoor tunnel with obstacles, tree swallows (Tachycineta bicolor) preferred larger openings, but we did not detect either individual or population-level side-biases. Thus, while observed behavioural side-biases during substrate-foraging and copulation are common in birds, we did not see such side-bias expressed in obstacle avoidance behaviour in flight. This finding highlights the importance of behavioural context for investigations of side-bias and hemispheric laterality and suggests both proximate and ultimate trade-offs between species-specific cognitive ecology and flight biomechanics

No evidence that footedness in pheasants influences cognitive performance in tasks assessing colour discrimination and spatial ability

The differential specialization of each side of the brain facilitates the parallel processing of information and has been documented in a wide range of animals. Animals that are more lateralized as indicated by consistent preferential limb use are commonly reported to exhibit superior cognitive ability as well as other behavioural advantages.We assayed the lateralization of 135 young pheasants (Phasianus colchicus), indicated by their footedness in a spontaneous stepping task, and related this measure to individual performance in either 3 assays of visual or spatial learning and memory. We found no evidence that pronounced footedness enhances cognitive ability in any of the tasks. We also found no evidence that an intermediate footedness relates to better cognitive performance. This lack of relationship is surprising because previous work revealed that pheasants have a slight population bias towards right footedness, and when released into the wild, individuals with higher degrees of footedness were more likely to die. One explanation for why extreme lateralization is constrained was that it led to poorer cognitive performance, or that optimal cognitive performance was associated with some intermediate level of lateralization. This stabilizing selection could explain the pattern of moderate lateralization that is seen in most non-human species that have been studied. However, we found no evidence in this study to support this explanation

Visual laterality in dolphins: importance of the familiarity of stimuli

<p>Abstract</p> <p>Background</p> <p>Many studies of cerebral asymmetries in different species lead, on the one hand, to a better understanding of the functions of each cerebral hemisphere and, on the other hand, to develop an evolutionary history of hemispheric laterality. Our animal model is particularly interesting because of its original evolutionary path, i.e. return to aquatic life after a terrestrial phase. The rare reports concerning visual laterality of marine mammals investigated mainly discrimination processes. As dolphins are migrant species they are confronted to a changing environment. Being able to categorize new versus familiar objects would allow dolphins a rapid adaptation to novel environments. Visual laterality could be a prerequisite to this adaptability. To date, no study, to our knowledge, has analyzed the environmental factors that could influence their visual laterality.</p> <p>Results</p> <p>We investigated visual laterality expressed spontaneously at the water surface by a group of five common bottlenose dolphins (<it>Tursiops truncatus</it>) in response to various stimuli. The stimuli presented ranged from very familiar objects (known and manipulated previously) to familiar objects (known but never manipulated) to unfamiliar objects (unknown, never seen previously). At the group level, dolphins used their left eye to observe very familiar objects and their right eye to observe unfamiliar objects. However, eyes are used indifferently to observe familiar objects with intermediate valence.</p> <p>Conclusion</p> <p>Our results suggest different visual cerebral processes based either on the global shape of well-known objects or on local details of unknown objects. Moreover, the manipulation of an object appears necessary for these dolphins to construct a global representation of an object enabling its immediate categorization for subsequent use. Our experimental results pointed out some cognitive capacities of dolphins which might be crucial for their wild life given their fission-fusion social system and migratory behaviour.</p

Lateralization of viewing and other functions in the domestic chick

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Hemispheric specialization and dual processing in strongly versus weakly lateralized chicks

Lateralization of various functions is well established in the domestic chick and other vertebrates. The function of lateralization is a question under investigation now. In a previous study, it was shown that chicks incubated in the dark (Da), which prevents the development of lateralization of visual foraging and predator detection, did not perform well when two tasks requiring simultaneous use of the expertise of the right and left eye systems were presented. Performance of a task requiring the chick to find grains against a background of pebbles deteriorated in the Da chicks in the presence of a predator. In the study reported here, the two simultaneous tasks were tested in both binocular and monocular conditions to establish the role of each eye system. Learning of the pebble-floor task was poor in Da chicks tested binocularly or monocularly and in the light-exposed (Li) chicks using the left eye (LE). The time taken to complete the pebble-floor task in the presence of a predator was significantly longer for the Da chicks. This was because pecking was interrupted for longer times when the predator was presented, and the Da chicks made more distress calls than the Li. The latency to detect the predator was longest in the Li chicks using the right eye (RE) (i.e., the Li were lateralized). In the Li chicks, sustained initial viewing of the predator was by the LE. There was no LE/RE difference in the Da chicks. The intensity of responses decreased with continued presentation of the predator but forced use of the RE slowed this habituation. Exposure to light before hatching affects lateralization of both learning of the pebble-floor task and the detection of an overhead predator. Attending to the foraging and predator vigilance tasks simultaneously is impaired in the Da chicks and the superior ability of Li (lateralized) chicks is due to a specific effect of light stimulation of the RE prior to hatching. We have shown that superior performance on the dual task results from the ability to allocate food searching to one hemisphere (left) and predator vigilance to the other (right) hemisphere, achieved only by Li chicks

The two hemispheres of the avian brain: their differing roles in perceptual processing and the expression of behavior

The hemispheres of the avian brain are specialized to carry out different functions. Since each eye sends its input mainly to the contralateral hemisphere, birds respond differently to stimuli seen with the left eye than they do to stimuli seen with the right eye. The right hemisphere attends to novel stimuli, which easily distract it from ongoing functions. It assumes control in emergency or stressful conditions. The left hemisphere attends to learnt categories and controls behavior in routine, non-stressful situations. This division of function extends to processing of auditory, olfactory and even magnetic stimuli. Evidence for this comes from a number of avian species, and has been shown in both laboratory and field tests. Knowledge of these specializations is relevant to understanding the behavior of birds in the wild since birds respond in different ways to stimuli on their left and right sides (e.g. preferential response to predators and conspecific on the left side and to prey on the right side) and they choose to view different stimuli with the left or right eye. Individual differences in the strength of visual lateralization are determined by exposure of the embryo to light, versus incubation in the dark, and by the levels of steroid hormones in ovo. The importance of these influences on lateralization is discussed in terms of behavior in the natural habitat. The potential importance of hemispheric dominance in the welfare of birds is also considered

Laterality as an indicator of emotional stress in ewes and lambs during a separation test

We assessed motor laterality in sheep to explore species-specific brain hemi-field dominance and how this could be affected by genetic or developmental factors. Further, we investigated whether directionality and strength of laterality could be linked to emotional stress in ewes and their lambs during partial separation. Forty-three ewes and their singleton lambs were scored on the (left/right) direction of turn in a y-maze to rejoin a conspecific (laterality test). Further, their behavioural response (i.e. time spent near the fence, vocalisations, and activity level) during forced separation by an open-mesh fence was assessed (separation test). Individual laterality was recorded for 44.2 % ewes (significant right bias) and 81.4 % lambs (equally biased to the left and the right). There was no significant association in side bias between dams and offspring. The Chi-squared test revealed a significant population bias for both groups (p &lt; 0.05). Evolutionary adaptive strategies or stimuli-related visual laterality may provide explanation for this decision-making process. Absolute strength of laterality (irrespective of side) was high (Kolmogorov–Smirnov test, dams: D = 0.2; p &lt; 0.001; lambs: D = 0.36, p &lt; 0.0001). The Wilcoxon test showed that lateralised lambs and dams spent significantly more time near each other during separation than non-lateralised animals (p &lt; 0.05), and that lateralised dams were also more active than non-lateralised ones. Arguably, the lateralised animals showed a greater attraction to their pair because they were more disturbed and thus required greater reassurance. The data show that measures of laterality offer a potential novel non-invasive indicator of separation stress.</p