Lateralization of social learning in the domestic chick, Gallus gallus domesticus: learning to avoid

Sensitivity to the role of an animated agent from observed interactions in newborn chicks (Gallus gallus)

Few month old human infants are able to detect the social roles of artificial agents and consistently choose the object behaving as 'approacher' rather than 'repulser'. This preference has been considered evidence of a pre-linguistic and pre-cultural origin of the social mind. Similar preferences have not been described in other species, though comparative data could help clarify the nature of this phenomenon and its evolutionary origin. In this study, we investigated sensitivity to the social role of an artificial agent in domestic chicks. Birds offer an excellent model to study the evolutionary roots of cognitive abilities, since they separated from mammals over 300 Ma. Moreover, the investigation of newly hatched chicks allows control for previous experience. After being exposed to computer-presented animations depicting an interaction among two agents, chicks underwent a free choice test among those same objects. While no initial evidence of a clear preference emerged from the planned analysis, chicks in the experimental condition showed a preference for the 'approacher' when controlling for side bias, mirroring human infants behaviour. This suggests the existence of an early ability to discriminate agents from their interactions, independent from any social experience.

Who goes where in couples and pairs? Effects of sex and handedness on side preferences in human dyads

There is increasing evidence that inter-individual interaction among conspecifics can cause population-level lateralization. Male-female and mother-infant dyads of several non-human species show lateralised position preferences, but such preferences have rarely been examined in humans. We observed 430 male-female human pairs and found a significant bias for males to walk on the right side of the pair. A survey measured side preferences in 93 left-handed and 92 right-handed women, and 96 left-handed and 99 right-handed men. When walking, and when sitting on a bench, males showed a significant side preference determined by their handedness, with left-handed men preferring to be on their partner's left side and right-handed men preferring to be on their partner's right side. Women did not show significant side preferences. When men are with their partner they show a preference for the side that facilitates the use of their dominant hand. We discuss possible reasons for the side preference, including males prefering to occupy the optimal "fight ready" side, and the influence of sex and handedness on the strength and direction of emotion lateralization.

Activation of the Nucleus Taeniae of the Amygdala by Umami Taste in Domestic Chicks (Gallus gallus)

In chickens, the sense of taste plays an important role in detecting nutrients and choosing feed. The molecular mechanisms underlying the taste-sensing system of chickens are well studied, but the neural mechanisms underlying taste reactivity have received less attention. Here we report the short-term taste behaviour of chickens towards umami and bitter (quinine) taste solutions and the associated neural activity in the nucleus taeniae of the amygdala, nucleus accumbens and lateral septum. We found that chickens had more contact with and drank greater volumes of umami than bitter or a water control, and that chicks displayed increased head shaking in response to bitter compared to the other tastes. We found that there was a higher neural activity, measured as c-Fos activation, in response to umami taste in the right hemisphere of the nucleus taeniae of the amygdala. In the left hemisphere, there was a higher c-Fos activation of the nucleus taeniae of the amygdala in response to bitter than in the right hemisphere. Our findings provide clear evidence that chickens respond differently to umami and bitter tastes, that there is a lateralised response to tastes at the neural level, and reveals a new function of the avian nucleus taeniae of the amygdala as a region processing reward information.

Brain Lateralization and Cognitive Capacity

One way to increase cognitive capacity is to avoid duplication of functions on the left and right sides of the brain. There is a convincing body of evidence showing that such asymmetry, or lateralization, occurs in a wide range of both vertebrate and invertebrate species. Each hemisphere of the brain can attend to different types of stimuli or to different aspects of the same stimulus and each hemisphere analyses information using different neural processes. A brain can engage in more than one task at the same time, as in monitoring for predators (right hemisphere) while searching for food (left hemisphere). Increased cognitive capacity is achieved if individuals are lateralized in one direction or the other. The advantages and disadvantages of individual lateralization are discussed. This paper argues that directional, or population-level, lateralization, which occurs when most individuals in a species have the same direction of lateralization, provides no additional increase in cognitive capacity compared to individual lateralization although directional lateralization is advantageous in social interactions. Strength of lateralization is considered, including the disadvantage of being very strongly lateralized. The role of brain commissures is also discussed with consideration of cognitive capacity.

Unlearned visual preferences for the head region in domestic chicks

Unlearned tendencies to approach animate creatures are of great adaptive value, especially for nidifugous social birds that need to react to the presence of potential social companions shortly after hatching. Domestic chicks’ preferences for taxidermized hens provided the first evidence of social predispositions. However, the nature of the stimuli eliciting this predisposition is not completely understood. Here we explore the unlearned preferences of visually naïve domestic chicks for taxidermized animals. Visually naive chicks were tested for their approach preferences between a target stimulus (an intact stuffed animal whose head region was clearly visible) and a control stimulus. After confirming the predisposition for the intact stuffed fowl hen (Exp. 1), we found an analogous preference for a taxidermized, young domestic chick over a severely scrambled version of the same stimulus, whose body structure was completely disrupted, extending to same-age individuals the results that had been obtained with taxidermized hens (Exp. 2). We also directly tested preferences for specimens whose head region is visible compared to ones whose head region was occluded. To clarify whether chicks are sensitive to species-specific information, we employed specimens of female mallard ducks and of a mammalian predator, the polecat. Chicks showed a preference for the duck stimulus whose wings have been covered over a similar stimulus whose head region has been covered, providing direct evidence that the visibility of the head region of taxidermized models drive chicks’ behaviour in this test, and that the attraction for the head region indeed extends to females of other bird species (Exp. 3). However, no similar preference was obtained with the polecat stimuli (Exp. 4). We thus confirmed the presence of unlearned visual preferences for the head region in newly-hatched chicks, though other factors can limit the species-generality of the phenomenon.

Does Functional Lateralization in Birds Have any Implications for Their Welfare?

We know a good deal about brain lateralization in birds and a good deal about animal welfare, but relatively little about whether there is a noteworthy relationship between avian welfare and brain lateralization. In birds, the left hemisphere is specialised to categorise stimuli and to discriminate preferred categories from distracting stimuli (e.g., food from an array of inedible objects), whereas the right hemisphere responds to small differences between stimuli, controls social behaviour, detects predators and controls attack, fear and escape responses. In this paper, we concentrate on visual lateralization and the effect of light exposure of the avian embryo on the development of lateralization, and we consider its role in the welfare of birds after hatching. Findings suggest that light-exposure during incubation has a general positive effect on post-hatching behaviour, likely because it facilitates control of behaviour by the left hemisphere, which can suppress fear and other distress behaviour controlled by the right hemisphere. In this context, particular attention needs to be paid to the influence of corticosterone, a stress hormone, on lateralization. Welfare of animals in captivity, as is well known, has two cornerstones: enrichment and reduction of stress. What is less well-known is the link between the influence of experience on brain lateralization and its consequent positive or negative outcomes on behaviour. We conclude that the welfare of birds may be diminished by failure to expose the developing embryos to light but we also recognise that more research on the association between lateralization and welfare is needed.

Context-dependent behavioural lateralization in the European pond turtle Emys orbicularis (Testudines, Emydidae)

Lateralization presents clear advantages in ecological contexts since dominance of one brain side prevents the simultaneous activation of contrasting responses in organisms with laterally located eyes. This is crucial in selecting a safe refuge during a predatory attack and may strongly affect predator–prey interactions. We explored the possible presence of lateralization in the antipredatory behaviour of European pond turtles, considering their escape facing a possible predatory attack. Thirty individuals (17 males, 13 females) were exposed to three different environmental situations of gradual increasing predatory threat: escape underwater from an unsafe shelter, diving into the water from a basking site, righting after being overturned. All turtles were tested 20 times for each of the three experiments (60 trials per individual and 1800 overall trials). We recorded multiple behavioural responses in the general context of predation risk. This was done in order to assess both the existence of lateralization and possible correlations among different behaviours as function of lateralization. The number of significant responses to the left side was always prevalent in each of the three simulated anti-predatory situations, suggesting the existence of a lateralized behaviour in this species. At the individual level, the differences we found in the three experiments could be related to different ecological contexts and consequent risk of predation. Our findings, among the few on Chelonians, support the possible involvement of the right hemisphere activity and, most importantly, reveal how the complexity of a general predatory context can affect the laterality of escape behaviour.

What can fish brains tell us about visual perception?

Fish are a complex taxonomic group, whose diversity and distance from other vertebrates well suits the comparative investigation of brain and behavior: in fish species we observe substantial differences with respect to the telencephalic organization of other vertebrates and an astonishing variety in the development and complexity of pallial structures. We will concentrate on the contribution of research on fish behavioral biology for the understanding of the evolution of the visual system. We shall review evidence concerning perceptual effects that reflect fundamental principles of the visual system functioning, highlighting the similarities and differences between distant fish groups and with other vertebrates. We will focus on perceptual effects reflecting some of the main tasks that the visual system must attain. In particular, we will deal with subjective contours and optical illusions, invariance effects, second order motion and biological motion and, finally, perceptual binding of object properties in a unified higher level representation.

Time-dependent lateralization of social learning in the domestic chick (Gallus gallus domesticus): Effects of retention delays in the observed lateralization pattern

Day-old chicks have been shown capable of learning to avoid pecking by observation only of a conspecific showing a disgust reaction after pecking a bitter-tasting bead. This learning is lateralized: access to the right hemisphere appears necessary for successful performance 30 min after training. This is in contrast to the non-social learning version of this learning task, in which the left hemisphere appears to play the dominant role, although both the left and right hemispheres are, in turn, subject to brief windows of "enhanced recall" during memory formation. In our present work we wished to investigate whether such recall events are also prevalent in the social learning task. We investigated 3 such windows; 25 min (a right hemisphere event), 32 min (left-hemisphere event) and 64 min (a possible left-hemisphere event following an interconnection of both hemispheres allowing memory transfer between the two hemispheres). At 32 and 64 min after training we found no evidence of functional lateralization. At 25 min, however, we found right hemisphere dominance. We suggest that a lateralization effect occurs in the social version of the PAL (passive avoidance learning) only at time points associated with right hemisphere dominance. It seems that lateralization is not able to emerge at time points where a left-hemisphere event is expected, because the two "lateralization effects" (right hemisphere dominance associated with the social task and left-hemisphere dominance associated with the PAL task) are in conflict.