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Sovrano, V.A.; Rainoldi, C.; Bisazza, A.; Vallortigara, G. |
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Title |
Roots of brain specializations: preferential left-eye use during mirror-image inspection in six species of teleost fish |
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Journal Article |
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1999 |
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Behavioural Brain Research |
Abbreviated Journal |
Behav. Brain. Res. |
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106 |
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1-2 |
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175-180 |
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Predator fixation; Fish; Left-eye preference |
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It has recently been reported that predator inspection is more likely to occur when a companion (i.e. the mirror image of the test animal) is visible on the left rather than on the right side of mosquitofish Gambusia holbrooki. This very unexpected outcome could be consistent with the hypothesis of a preferential use of the right eye during sustained fixation of a predator as well as of a preferential use of the left eye during fixation of conspecifics. We measured the time spent in monocular viewing during inspection of their own mirror images in females of six species of fish, belonging to different families--G. holbrooki, Xenotoca eiseni, Phoxinus phoxinus, Pterophyllum scalare, Xenopoecilus sarasinorum, and Trichogaster trichopterus. Results revealed a consistent left-eye preference during sustained fixation in all of the five species. Males of G. holbrooki, which do not normally show any social behaviour, did not exhibit any eye preferences during mirror-image inspection. We found, however, that they could be induced to manifest a left-eye preference, likewise females, if tested soon after capture, when some affiliative tendencies can be observed. These findings add to current evidence in a variety of vertebrate species for preferential involvement of structures located in the right side of the brain in response to the viewing of conspecifics. |
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614 |
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Author |
Ghirlanda, S.; Vallortigara, G. |
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Title |
The evolution of brain lateralization: a game-theoretical analysis of population structure |
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Journal Article |
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2004 |
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Proceedings of the Royal Society of London. Series B: Biological Sciences |
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271 |
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1541 |
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853-857 |
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In recent years, it has become apparent that behavioural and brain lateralization at the population level is the rule rather than the exception among vertebrates. The study of these phenomena has so far been the province of neurology and neuropsychology. Here, we show how such research can be integrated with evolutionary biology to understand lateralization more fully. In particular, we address the fact that, within a species, left– and right–type individuals often occur in proportions different from one–half (e.g. hand use in humans). The traditional explanations offered for lateralization of brain function (that it may avoid unnecessary duplication of neural circuitry and reduce interference between functions) cannot account for this fact, because increased individual efficiency is unrelated to the alignment of lateralization at the population level. A further puzzle is that such an alignment may even be disadvantageous, as it makes individual behaviour more predictable to other organisms. Here, we show that alignment of the direction of behavioural asymmetries in a population can arise as an evolutionarily stable strategy when individual asymmetrical organisms must coordinate their behaviour with that of other asymmetrical organisms. Brain and behavioural lateralization, as we know it in humans and other vertebrates, may have evolved under basically ‘social’ selection pressures. |
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Equine Behaviour @ team @ |
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5345 |
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Ghirlanda, S.; Frasnelli, E.; Vallortigara, G. |
![goto web page (via DOI) doi](img/doi.gif)
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Title |
Intraspecific competition and coordination in the evolution of lateralization |
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2009 |
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Philosophical Transactions of the Royal Society B: Biological Sciences |
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Phil. Trans. Biol. Sci. |
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364 |
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1519 |
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861-866 |
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Recent studies have revealed a variety of left–right asymmetries among vertebrates and invertebrates. In many species, left- and right-lateralized individuals coexist, but in unequal numbers (‘population-level’ lateralization). It has been argued that brain lateralization increases individual efficiency (e.g. avoiding unnecessary duplication of neural circuitry and reducing interference between functions), thus counteracting the ecological disadvantages of lateral biases in behaviour (making individual behaviour more predictable to other organisms). However, individual efficiency does not require a definite proportion of left- and right-lateralized individuals. Thus, such arguments do not explain population-level lateralization. We have previously shown that, in the context of prey–predator interactions, population-level lateralization can arise as an evolutionarily stable strategy when individually asymmetrical organisms must coordinate their behaviour with that of other asymmetrical organisms. Here, we extend our model showing that populations consisting of left- and right-lateralized individuals in unequal numbers can be evolutionarily stable, based solely on strategic factors arising from the balance between antagonistic (competitive) and synergistic (cooperative) interactions. |
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Equine Behaviour @ team @ |
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5346 |
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Author |
Regolin, L.; Tommasi, L.; Vallortigara, G. |
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Title |
Visual perception of biological motion in newly hatched chicks as revealed by an imprinting procedure |
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Year |
2000 |
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Animal Cognition |
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Anim. Cogn. |
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3 |
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1 |
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53-60 |
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Day-old chicks were exposed to point-light animation sequences depicting either a walking hen or a rotating cylinder. On a subsequent free-choice test (experiment 1) the chicks approached the novel stimulus, irrespective of this being the hen or the cylinder. In order to obtain equivalent local motion vectors, in experiments 2 and 3 newly hatched chicks were exposed either to a point-light animation sequence depicting a walking hen, or to a positionally scrambled walking hen (i.e. an animation in which exactly the same set of dots in motion as that employed for the walking hen was presented, but with spatially randomized starting positions). Chicks tested on day 1 (experiment 2) or on day 2 (i.e. after a period in the dark following exposure on day 1 (experiment 3)) proved able to discriminate the two animation sequences: males preferentially approached the novel stimulus, females the familiar one. These results indicate that discrimination was not based on local motion vectors, but rather on the temporally integrated motion sequence. |
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Equine Behaviour @ team @ |
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3314 |
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Author |
Vallortigara, G.; Regolin, L.; Rigoni, M.; Zanforlin, M. |
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Title |
Delayed search for a concealed imprinted object in the domestic chick |
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Journal Article |
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Year |
1998 |
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Animal Cognition |
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Anim. Cogn. |
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1 |
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1 |
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17-24 |
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Five-day-old chicks were accustomed to follow an imprinted object (a small red ball with which they had been reared) that was moving slowly in a large arena, until it disappeared behind an opaque screen. In experiments, each chick was initially confined in a transparent cage, from where it could see and track the ball while it moved towards, and then beyond, one of two screens. The screens could be either identical or differ in colour and pattern. Either immediately after the disappearance of the ball, or with a certain delay, the chick was released and allowed to search for its imprinted object behind either screen. The results showed that chicks took into account the directional cue provided by the ball movement and its concealment, up to a delay period of about 180 s, independently of the perceptual characteristics of the two screens. If an opaque partition was positioned in front of the transparent cage immediately after the ball had disappeared, so that, throughout the delay, neither the goal-object nor the two screens were visible, chicks were still capable of remembering and choosing the correct screen, though over a much shorter period of about 60 s. The results suggest that, at least in this precocial bird species, very young chicks can maintain some form of representation of the location where a social partner was last seen, and are also capable of continuously updating this representation so as to take into account successive displacements of the goal-object. |
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Equine Behaviour @ team @ |
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3347 |
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