Kinship and familiarity as factors affecting social transfer of food preferences in adult Mongolian gerbils (Meriones unguiculatus)

Sensory cortex plasticity supports auditory social learning

Social learning (SL) through experience with conspecifics can facilitate the acquisition of many behaviors. Thus, when Mongolian gerbils are exposed to a demonstrator performing an auditory discrimination task, their subsequent task acquisition is facilitated, even in the absence of visual cues. Here, we show that transient inactivation of auditory cortex (AC) during exposure caused a significant delay in task acquisition during the subsequent practice phase, suggesting that AC activity is necessary for SL. Moreover, social exposure induced an improvement in AC neuron sensitivity to auditory task cues. The magnitude of neural change during exposure correlated with task acquisition during practice. In contrast, exposure to only auditory task cues led to poorer neurometric and behavioral outcomes. Finally, social information during exposure was encoded in the AC of observer animals. Together, our results suggest that auditory SL is supported by AC neuron plasticity occurring during social exposure and prior to behavioral performance.

From whom do animals learn? A meta-analysis on model-based social learning

Social learning via the observation of or interaction with other individuals can allow animals to obtain information about the local environment. Once social information is obtained, animals may or may not act on and use this information. Animals may learn from others selectively based on particular characteristics (e.g., familiarity, age, dominance) of the information provider, which is thought to maximize the benefits of social learning. Biases to copy certain individuals over others plays an important role in how information is transmitted and used among individuals, and can influence the emergence of group-level behaviors (i.e., traditions). Two underlying factors can affect from whom animals learn: the population social dynamics - with whom you associate (e.g., familiar), and status of the demonstrator (e.g., dominant). We systematically surveyed the literature and conducted a meta-analysis to test whether demonstrator characteristics consistently influence social learning, and if social dynamics strategies differ from status strategies in their influence on social learning. We extracted effect sizes from papers that used an observer-demonstrator paradigm to test if the characteristics of the individual providing social information (i.e., the demonstrator) influence social information use by observers. We obtained 139 effect sizes on 33 species from 54 experiments. First, we found an effect of experimental design on the influence of demonstrator characteristics on social learning: between-subject designs had stronger effects compared to within-subject designs. Second, we found that demonstrator characteristics do indeed influence social learning. Characteristics based on social dynamics and characteristics based on status had a significant effect on social learning, especially when copying familiar and kin demonstrators. These results highlight the role that demonstrator characteristics play on social learning, which can have implications for the formation and establishment of behavioural traditions in animals.

Group size and modularity interact to shape the spread of infection and information through animal societies

Social interactions between animals can provide many benefits, including the ability to gain useful environmental information through social learning. However, these social contacts can also facilitate the transmission of infectious diseases through a population. Animals engaging in social interactions therefore face a trade-off between the potential informational benefits and the risk of acquiring disease. Theoretical models have suggested that modular social networks, associated with the formation of groups or sub-groups, can slow spread of infection by trapping it within particular groups. However, these social structures will not necessarily impact the spread of information in the same way if its transmission follows a “complex contagion”, e.g. through individuals disproportionally copying the majority (conformist learning). Here we use simulation models to demonstrate that modular networks can promote the spread of information relative to the spread of infection, but only when the network is fragmented and group sizes are small. We show that the difference in transmission between information and disease is maximised for more well-connected social networks when the likelihood of transmission is intermediate. Our results have important implications for understanding the selective pressures operating on the social structure of animal societies, revealing that highly fragmented networks such as those formed in fission–fusion social groups and multilevel societies can be effective in modulating the infection-information trade-off for individuals within them.

Ability to share emotions of others as a foundation of social learning

The natural habitats of most species are far from static, forcing animals to adapt to continuously changing conditions. Perhaps the most efficient strategy addressing this challenge consists of obtaining and acting upon pertinent information from others through social learning. We discuss how animals transfer information via social channels and what are the benefits of such exchanges, playing out on different levels, from theperception of socially delivered information to emotional sharing, manifesting themselves across different taxa of increasing biological complexity. We also discuss how social learning is influenced by different factors including pertinence of information for survival, the complexity of the environment, sex, genetic relatedness, and most notably, the relationship between interacting partners. The results appear to form a consistent picture once we shift our focus from emotional contagion as a prerequisite for empathy onto the role of shared emotions in providing vital information about the environment. From this point of view, we can propose approaches that are the most promising for further investigation of complex social phenomena, including learning from others.

Odor-based mate choice copying in deer mice is not affected by familiarity or kinship

Individuals pay attention to the social and mate decisions of others and use these to determine their own choices, displaying mate choice copying. The present study with deer mice, Peromyscus maniculatus, showed that females copied the odor preferences and appetitive components of the mate choice of other females. It was found that an association between male and female odors, which is indicative of the apparent interest expressed by a female in a male, enhanced the preference of another female for the odors of that male. This socially learned odor preference lasted for at least 24 h and extended to a preference for the actual male that was the odor source. Neither kinship nor prior familiarity with the female whose odor was presented had a significant influence on the degree of odor-based mate choice copying displayed. These findings show that female deer mice can engage in mate choice copying using the odor-based social interest and mate choice of other females.

Evaluating and re-evaluating intra- and inter-species social transmission of food preferences in domestic dogs

Social-transmission of food preference is a robust behavioral phenomenon in rodents and other species, but less work has evaluated this phenomenon in broader taxa and to what degree social-transmission can occur between species. Here we show that over the span of three experiments that consisted of a human-dog, a dog-dog, and a replication study of a dog-dog demonstrator-observer test, we did not observe successful social transmission of food preferences across all three experiments. For our first experiment, we investigated whether pet dogs acquire food preference from their owners using a two-bowl preference test. The results suggested that our dogs did not acquire a preference for the flavor consumed by their owners. This then led us to investigate whether this failure was the result of an inter-species failure, so we replicated the experiment using two familiar dogs as the demonstrator and observer. The results for Experiment Two also suggested that our participant dogs do not acquire food preference from a canine demonstrator. A third experiment attempted a direct replication of the Lupfer-Johnson and Ross (2007) that found dog-dog transmission of food preferences. Our results again indicated that our participant dogs did not acquire food preference from demonstrators. Over the span of three experiments, our results did not show clear canine food preferences for the food consumed by a demonstrator (human or dog).

Social learning exploits the available auditory or visual cues

The ability to acquire a behavior can be facilitated by exposure to a conspecific demonstrator. Such social learning occurs under a range of conditions in nature. Here, we tested the idea that social learning can benefit from any available sensory cue, thereby permitting learning under different natural conditions. The ability of naïve gerbils to learn a sound discrimination task following 5 days of exposure adjacent to a demonstrator gerbil was tested in the presence or absence of visual cues. Naïve gerbils acquired the task significantly faster in either condition, as compared to controls. We also found that exposure to a demonstrator was more potent in facilitating learning, as compared to exposure to the sounds used to perform the discrimination task. Therefore, social learning was found to be flexible and equally efficient in the auditory or visual domains.

Does demonstrator relevance affect social preferences and the social transmission of food preferences in female mice (Mus musculus)?

This study examined whether a history of beneficial social learning experiences affects social partner preferences in laboratory mice (Mus musculus) and whether observer mice acquire adaptive model-based social learning strategies through associative learning. We tested whether observers would come to socially prefer demonstrators who provide beneficial information through the social transmission of food preference (STFP), over demonstrators who do not; and whether they would preferentially attend to and learn from such demonstrators. Observers were given repeated exposures to two demonstrators who differed in whether or not they consistently provided beneficial information (which increased observers' ingestion of food via the STFP). After multiple social learning experiences with a "relevant demonstrator" (our CS+) whose demonstrated food was available for consumption (our US) by the observer and a "non-relevant demonstrator" whose demonstrated food was never encountered, neither demonstrator was preferred over the other. Furthermore, observers learned equally well from both relevant and non-relevant demonstrators. The present findings suggest that adaptive model-based social learning strategies are not followed in the STFP, although we recommend further testing of the social preference hypothesis.

The role of social cognition in parasite and pathogen avoidance

The acquisition and use of social information are integral to social behaviour and parasite/pathogen avoidance. This involves social cognition which encompasses mechanisms for acquiring, processing, retaining and acting on social information. Social cognition entails the acquisition of social information about others (i.e. social recognition) and from others (i.e. social learning). Social cognition involves assessing other individuals and their infection status and the pathogen and parasite threat they pose and deciding about when and how to interact with them. Social cognition provides a framework for examining pathogen and parasite avoidance behaviours and their associated neurobiological mechanisms. Here, we briefly consider the relationships between social cognition and olfactory-mediated pathogen and parasite avoidance behaviours. We briefly discuss aspects of (i) social recognition of actual and potentially infected individuals and the impact of parasite/pathogen threat on mate and social partner choice; (ii) the roles of 'out-groups' (strangers, unfamiliar individuals) and 'in-groups' (familiar individuals) in the expression of parasite/pathogen avoidance behaviours; (iii) individual and social learning, i.e. the utilization of the pathogen recognition and avoidance responses of others; and (iv) the neurobiological mechanisms, in particular the roles of the nonapeptide, oxytocin and steroid hormones (oestrogens) associated with social cognition and parasite/pathogen avoidance.This article is part of the Theo Murphy meeting issue 'Evolution of pathogen and parasite avoidance behaviours'.

Aversive Foraging Conditions Modulate Downstream Social Food Sharing

Eusocial insects divide their labour so that individuals working inside the nest are affected by external conditions through a cascade of social interactions. Honey bees (Apis mellifera) transfer food and information via mouth-to-mouth social feeding, ie trophallaxis, a process known to be modulated by the rate of food flow at feeders and familiarity of food's scent. Little is understood about how aversive foraging conditions such as predation and con-specific competition affect trophallaxis. We hypothesized that aversive conditions have an impact on food transfer inside the colony. Here we explore the effect of foragers' aversive experience on downstream trophallaxis in a cage paradigm. Each cage contained one group of bees that was separated from feeders by mesh and allowed to feed only through trophallaxis, and another group that had access to feeders and self-specialized to either forage or distribute food. Our results show that aversive foraging conditions increase non-foragers' trophallaxis with bees restricted from feeder access when food is scented, and have the opposite effect when food is unscented. We discuss potential behavioural mechanisms and implications for the impact of aversive conditions such as malaise inducing toxins, predation, and con-specific competition.

Social learning in otters

The use of information provided by others to tackle life's challenges is widespread, but should not be employed indiscriminately if it is to be adaptive. Evidence is accumulating that animals are indeed selective and adopt 'social learning strategies'. However, studies have generally focused on fish, bird and primate species. Here we extend research on social learning strategies to a taxonomic group that has been neglected until now: otters (subfamily Lutrinae). We collected social association data on captive groups of two gregarious species: smooth-coated otters (Lutrogale perspicillata), known to hunt fish cooperatively in the wild, and Asian short-clawed otters (Aonyx cinereus), which feed individually on prey requiring extractive foraging behaviours. We then presented otter groups with a series of novel foraging tasks, and inferred social transmission of task solutions with network-based diffusion analysis. We show that smooth-coated otters can socially learn how to exploit novel food sources and may adopt a 'copy when young' strategy. We found no evidence for social learning in the Asian short-clawed otters. Otters are thus a promising model system for comparative research into social learning strategies, while conservation reintroduction programmes may benefit from facilitating the social transmission of survival skills in these vulnerable species.

Mate-choice copying, social information processing, and the roles of oxytocin

Social and sexual behaviors, including that of mate choice, are dependent on social information. Mate choice can be modified by prior and ongoing social factors and experience. The mate choice decisions of one individual can be influenced by either the actual or potential mate choice of another female or male. Such non-independent mate choice, where individuals gain social information and socially learn about and recognizes potential mates by observing the choices of another female or male, has been termed "mate-choice copying". Here we first briefly review how, why, and under what circumstances individuals engage in mate-choice copying. Secondly, we review the neurobiological mechanisms underlying mate-choice copying. In particular, we consider the roles of the nonapeptide, oxytocin, in the processing of social information and the expression of mate-choice copying.

When does social learning become cultural learning?

Developmental research on selective social learning, or 'social learning strategies', is currently a rich source of information about when children copy behaviour, and who they prefer to copy. It also has the potential to tell us when and how human social learning becomes cultural learning; i.e. mediated by psychological mechanisms that are specialized, genetically or culturally, to promote cultural inheritance. However, this review article argues that, to realize its potential, research on the development of selective social learning needs more clearly to distinguish functional from mechanistic explanation; to achieve integration with research on attention and learning in adult humans and 'dumb' animals; and to recognize that psychological mechanisms can be specialized, not only by genetic evolution, but also by associative learning and cultural evolution.

Estrogen involvement in social behavior in rodents: Rapid and long-term actions

This article is part of a Special Issue ("Estradiol and cognition"). Estrogens have repeatedly been shown to influence a wide array of social behaviors, which in rodents are predominantly olfactory-mediated. Estrogens are involved in social behavior at multiple levels of processing, from the detection and integration of socially relevant olfactory information to more complex social behaviors, including social preferences, aggression and dominance, and learning and memory for social stimuli (e.g. social recognition and social learning). Three estrogen receptors (ERs), ERα, ERβ, and the G protein-coupled ER 1 (GPER1), differently affect these behaviors. Social recognition, territorial aggression, and sexual preferences and mate choice, all requiring the integration of socially related olfactory information, seem to primarily involve ERα, with ERβ playing a lesser, modulatory role. In contrast, social learning consistently responds differently to estrogen manipulations than other social behaviors. This suggests differential ER involvement in brain regions important for specific social behaviors, such as the ventromedial and medial preoptic nuclei of the hypothalamus in social preferences and aggression, the medial amygdala and hippocampus in social recognition, and the prefrontal cortex and hippocampus in social learning. While the long-term effects of ERα and ERβ on social behavior have been extensively investigated, our knowledge of the rapid, non-genomic, effects of estrogens is more limited and suggests that they may mediate some social behaviors (e.g. social learning) differently from long-term effects. Further research is required to compare ER involvement in regulating social behavior in male and female animals, and to further elucidate the roles of the more recently described G protein-coupled ERs, both the GPER1 and the Gq-mER.

Rapid oestrogenic regulation of social and nonsocial learning

Much research on oestrogens has focused on their long-term action, exerting behavioural effects within hours to days through gene transcription. Oestrogens also affect behaviour on a much shorter time scale. These rapid effects are assumed to occur through cell signalling and can elicit a behavioural effect as early as 15 min after treatment. These effects on behaviour have primarily been explored through the action of oestradiol at three well-known oestrogen receptors (ERs): ERα, ERβ and the more recently described G protein-coupled ER1 (GPER1). The rapid effects of oestradiol and ER agonists have been tested on both social and nonsocial learning paradigms. Social learning refers to a paradigm in which an animal acquires information and modifies its behaviour based on observation of another animal, commonly studied using the social transmission of food preferences paradigm. When administered shortly before testing, oestradiol rapidly improves social learning on this task, although no ER agonist has definitive, comparable improving effects. Some evidence points to GPER1, whereas ERα impairs, and ERβ activation has no effect on social learning. Conversely, ERα and GPER1 play a larger role than ERβ in the rapid improving effect of oestrogens on nonsocial learning, including social and object recognition. In addition, when administered immediately post-acquisition, oestrogens also rapidly improve memory consolidation in a variety of learning paradigms: object recognition, object placement, inhibitory avoidance and the Morris water maze, indicating that oestradiol affects the consolidation of multiple types of memory. Evidence suggests that these improvements are the result of oestrogens acting in the dorsal hippocampus where selective activation of all three ERs shows rapid improving effects on spatial learning comparable to oestradiol. However, the hippocampus is not necessary for rapid oestradiol improvements on social recognition. Although acute treatment with oestradiol enhances learning and memory on various social and nonsocial learning paradigms, the specific ERs play different roles in each type of learning. Future research should aim to further determine the roles of ERs with respect to the enhancing effects of oestradiol on learning and memory, and also determine where in the brain oestradiol acts to affect social and nonsocial learning.

Estrogenic involvement in social learning, social recognition and pathogen avoidance

Sociality comes with specific cognitive skills that allow the proper processing of information about others (social recognition), as well as of information originating from others (social learning). Because sociality and social interactions can also facilitate the spread of infection among individuals the ability to recognize and avoid pathogen threat is also essential. We review here various studies primarily from the rodent literature supporting estrogenic involvement in the regulation of social recognition, social learning (socially acquired food preferences and mate choice copying) and the recognition and avoidance of infected and potentially infected individuals. We consider both genomic and rapid estrogenic effects involving estrogen receptors α and β, and G-protein coupled estrogen receptor 1, along with their interactions with neuropeptide systems in the processing of social stimuli and the regulation and expression of these various socially relevant behaviors.

Differential effects of dopamine receptor D1-type and D2-type antagonists and phase of the estrous cycle on social learning of food preferences, feeding, and social interactions in mice

The neurobiological bases of social learning, by which an animal can 'exploit the expertise of others' and avoid the disadvantages of individual learning, are only partially understood. We examined the involvement of the dopaminergic system in social learning by administering a dopamine D1-type receptor antagonist, SCH23390 (0.01, 0.05, and 0.1 mg/kg), or a D2-type receptor antagonist, raclopride (0.1, 0.3, and 0.6 mg/kg), to adult female mice prior to socially learning a food preference. We found that while SCH23390 dose-dependently inhibited social learning without affecting feeding behavior or the ability of mice to discriminate between differently flavored diets, raclopride had the opposite effects, inhibiting feeding but leaving social learning unaffected. We showed that food odor, alone or in a social context, was insufficient to induce a food preference, proving the specifically social nature of this paradigm. The estrous cycle also affected social learning, with mice in proestrus expressing the socially acquired food preference longer than estrous and diestrous mice. This suggests gonadal hormone involvement, which is consistent with known estrogenic regulation of female social behavior and estrogen receptor involvement in social learning. Furthermore, a detailed ethological analysis of the social interactions during which social learning occurs showed raclopride- and estrous phase-induced changes in agonistic behavior, which were not directly related to effects on social learning. Overall, these results suggest a differential involvement of the D1-type and D2-type receptors in the regulation of social learning, feeding, and agonistic behaviors that are likely mediated by different underlying states.

Neuroendocrinology of social information processing in rats and mice

We reviewed oxytocin (OT), arginine-vasopressin (AVP) and gonadal hormone involvement in various modes of social information processing in mice and rats. Gonadal hormones regulate OT and AVP mediation of social recognition and social learning. Estrogens foster OT-mediated social recognition and the recognition and avoidance of parasitized conspecifics via estrogen receptor (ER) alpha (ERalpha) and ERbeta. Testosterone and its metabolites, including estrogens, regulate social recognition in males predominantly via the AVP V1a receptor. Both OT and AVP are involved in the social transmission of food preferences and ERalpha has inhibitory, while ERbeta has enhancing, roles. OT also enhances mate copying by females. ERalpha mediates the sexual, and ERbeta the recognition, aspects of the risk-taking enhancing effects of females on males. Thus, androgens and estrogens control social information processing by regulating OT and AVP. This control is finely tuned for different forms of social information processing.

Social interaction and partner familiarity differentially alter voluntary ethanol intake in adolescent male and female rats

Alcohol readily facilitates social interactions and this effect plays an important role in adolescent drinking behaviors. The ability of social interaction to alter behaviors in response to alcohol in adolescent animals has been assessed using the demonstrator-observer paradigm. The demonstrator is exposed to ethanol and the observer is tested for changes in behaviors in response to ethanol after social interaction between the dyad. The present experiment expanded on previous work to investigate the effects of different types of social interaction on subsequent voluntary ethanol consumption in adolescent male and female rats. Specifically, voluntary ethanol intake was assessed in adolescent observers after social interaction with an alcohol-free or -intoxicated same-sex familiar cage-mate or an age-matched unfamiliar conspecific. Demonstrators were intragastrically administered water or 1.5 g/kg ethanol and allowed to socially interact with observers for 30 min after a 1-h social isolation period. Subsequently, observers were allowed voluntary access to ethanol using a two-bottle choice paradigm overnight for 13 h. Male and female observers that interacted with an alcohol-intoxicated familiar cagemate consumed significantly more ethanol relative to their alcohol-free counterparts. However, adolescent male observers that socially interacted with an alcohol-intoxicated, age-matched unfamiliar conspecific consumed significantly less ethanol than controls. The opposite effect was observed in adolescent female observers. The present results are consistent and extend previous work in support of the idea that exposure to the demonstrator-observer paradigm alters voluntary ethanol intake in a sex- and familiarity-dependent manner. Partner familiarity can induce elevated or reduced ethanol consumption in males. However, females appear to be more sensitive to the elevating effects of social interaction on voluntary ethanol consumption, regardless of familiarity of the partner.

Differential effects of estrogen receptor alpha and beta specific agonists on social learning of food preferences in female mice

There is an evolutionary advantage to learning food preferences from conspecifics, as social learning allows an individual to bypass the risks associated with trial and error individual learning. The social transmission of food preferences (STFP) paradigm examines this advantage. Females in the proestrus and diestrus phases of the estrous cycle show a prolonged preference for the demonstrated food relative to estrus and ovariectomized females. Additionally, both estrogen receptor alpha (ERalpha) and estrogen receptor beta (ERbeta) knockout mice show impaired social recognition, which suggests that both receptors may be involved in other types of socially dependent learning, including the STFP. The present study investigated the effect of the ERalpha selective agonist PPT (1,3,5-tris(4-hydroxyphenyl)-4-propyl-1H-pyrazole) and the ERbeta selective agonist WAY-200070 (7-Bromo-2-(4-hydroxyphenyl)-1,3-benzoxazol-5-ol) on the STFP. Results showed that ovariectomized (ovx) mice treated with PPT failed to learn the socially acquired preference, while WAY-200070-treated ovx mice showed a two-fold prolonged preference for the food eaten by their demonstrator. The effects of PPT on the socially acquired food preference cannot be explained by effects on the total food intake of the groups or on the type of interaction with the demonstrator mouse. The effects of WAY-200070 may be partially due to effects on Submissive Behavior. The higher WAY-200070 doses produced prolonged preferences similar to those seen previously in intact female mice during the proestrus and diestrus phases. This suggests that the estrous cycle's effects on social learning may be due to the action of ERbeta on Submissive Behavior, or to ERbeta countering that of ERalpha.

Preferential learning from non-affiliated individuals in jackdaws (Corvus monedula)

It has been suggested that affiliated social relations may facilitate information transfer between individuals. We here tested this rarely examined hypothesis with juvenile and adult jackdaws (Corvus monedula) in three stimulus enhancement tasks, both in a non-food context (experiment 1) and in a food context (experiments 2 and 3). We first show that siblings and pair partners maintain stronger bonded social relations than do non-siblings and non-pair partners. We therefore tested individuals in sibling and non-sibling dyads and, later in ontogeny, in pair and non-pair dyads. Jackdaws either did not learn from any other conspecific (experiment 1), or they learned from non-affiliated individuals (non-siblings, non-pair partners in experiments 2 and 3). This may be related to two main characteristics of jackdaws' affiliated relationships. First, affiliates share food at a high rate and may rely on their knowledgeable partners to secure food rather than learning from them. Second, affiliates spend most time in close spatial proximity to each other which increases the probability that they simultaneously experience occurrences in their environment. Hence, spatially more distant individuals, which are more likely to be non-affiliated, face different foraging situations and may therefore provide more relevant information which may lead to selective social learning.

Dogs acquire food preferences from interacting with recently fed conspecifics

Social transmission of food preferences has been documented in many species including humans, rodents, and birds. In the current experiment, 12 pairs of domestic dogs (Canis familiaris) were utilized. Within each pair, one dog (the demonstrator) was fed dry dog food flavored with either basil or thyme. The second dog (the observer) interacted with one demonstrator for 10 min before being given an equal amount of both flavored foods. Observers exhibited a significant preference for the flavored diet consumed by their demonstrators, indicating that dogs, like rats, prefer foods smelled on a conspecific's breath.

Neural encoding of olfactory recognition memory

Our work with both sheep and mouse models has revealed many of the neural substrates and signalling pathways involved in olfactory recognition memory in the main olfactory system. A distributed neural system is required for initial memory formation and its short-term retention-the olfactory bulb, piriform and entorhinal cortices and hippocampus. Following memory consolidation, after 8 h or so, only the olfactory bulb and piriform cortex appear to be important for effective recall. Similarly, whereas the glutamate-NMDA/AMPA receptor-nitric oxide (NO)-cyclic GMP signalling pathway is important for memory formation it is not involved in recall post-consolidation. Here, within the olfactory bulb, up-regulation of class 1 metabotropic glutamate receptors appears to maintain the enhanced sensitivity at the mitral to granule cell synapses required for effective memory recall. Recently we have investigated whether fluctuating sex hormone levels during the oestrous cycle modulate olfactory recognition memory and the different neural substrates and signalling pathways involved. These studies have used two robust models of social olfactory memory in the mouse which either involve social or non social odours (habituation-dishabituation and social transmission of food preference tasks). In both cases significant improvement of learning retention occurs when original learning takes place during the proestrus phase of the ovarian cycle. This is probably the result of oestrogen changes at this time since transgenic mice lacking functional expression of oestrogen receptors (ERalpha and ERbeta, the two main oestrogen receptor sub-types) have shown problems in social recognition. Therefore, oestrogen appears to act at the level of the olfactory bulb by modulating both noradrenaline and the glutamate/NO signalling pathway.

Lack of interference in long-term memory for socially learned food preferences in rats (Rattus norvegicus)

Outside the laboratory, rats (Rattus norvegicus) are likely both to interact with several conspecifics that have eaten various foods and to eat a variety of foods themselves before they encounter any particular food for which they have a socially enhanced preference. Here the authors examine the stability of rats' socially learned food preferences following 6 days of potentially disruptive ingestive experiences. The authors found that 6 days of (a) eating unfamiliar foods, (b) interacting with demonstrators that had eaten unfamiliar foods, or (c) both eating unfamiliar foods and interacting with demonstrators that had eaten those foods had no measurable effect on rats' socially learned food preferences. The stability of socially enhanced food preferences over time and despite potentially disruptive experiences is consistent with the view that social learning about foods is an important determinant of the food choices of free-living Norway rats.

Socially mediated alcohol preferences in adolescent rats following interactions with an intoxicated peer

This study focuses on "passive social influences" (alcohol-related information acquired by an organism that interacts with an intoxicated counterpart) that can potentially affect alcohol preference in adolescent rats. Five experiments were conducted to investigate whether repeated social interactions with an intoxicated peer can generate alcohol-related memories that lead an animal to exhibit heightened alcohol olfactory preference patterns. Juvenile experiences with alcohol were operationalized as follows: interactions with an alcohol-intoxicated peer (Experiment 1), with an alcohol-scented cotton surrogate (Experiment 2) or with an anesthetized alcohol-intoxicated partner (Experiments 3-5). Periadolescents were then evaluated in a two-way location olfactory test where they had the opportunity to investigate a hole scented with alcohol odor or vanilla (an odorant naturally preferred by the strain of rats here utilized). Only juveniles that interacted with an alcohol-intoxicated peer were found to exhibit a significant change in alcohol odor preferences when compared to appropriate controls that interacted with a non-intoxicated peer. Alcohol odor exposure alone or interactions with an anesthetized alcohol-intoxicated peer were not sufficient to establish changes in preference for alcohol sensory cues. Results indicate that social interactions with an intoxicated peer determine heightened preference for alcohol cues in periadolescents. The establishment of this preference seems to require behavioral manifestations of the intoxicated counterpart, instead of just being dependent on an olfactory pre-exposure to alcohol cues.

Social Transmission of Flavor Preferences in Two Species of Hamsters (Mesocricetus auratus and Phodopus campbelli)

Golden hamsters (Mesocricetus auratus) and dwarf hamsters (Phodopus campbelli) interacted with a conspecific demonstrator that had recently consumed a flavored food. When given a choice between their demonstrator's flavor and another flavor, the dwarf hamsters preferred the flavor their demonstrator had eaten. Golden hamsters did not prefer their demonstrators' diets when the demonstrators were unrelated adults or littermates, but they did when the demonstrator was their mother. Videotaping the interactions between demonstrators and observers revealed that adult golden hamsters did not investigate foods hoarded by their demonstrators whereas dwarf hamsters did. These results are interpreted in terms of the stimuli that activate feeding behavior systems in these 2 hamster species.

Social influences on foraging in vertebrates: causal mechanisms and adaptive functions

We summarize 20 years of empirical and theoretical research on causes and functions of social influences on foraging by animals. We consider separately studies of social influence on when, where, what and how to eat. Implicit in discussion of the majority of studies is our assumption that social influences on foraging reflect a biasing of individual learning processes by social stimuli rather than action of independent social-learning mechanisms. Our review of theoretical approaches suggests that the majority of formally derived hypotheses concerning functions of social influence on foraging have not yet been tested adequately and many models are in need of further refinement. We also consider the importance to the future of the field of integrating 'top-down' and 'bottom-up' approaches to the study of social learning. Copyright 2001 The Association for the Study of Animal Behaviour.

Seeing group members eating a familiar food enhances the acceptance of novel foods in capuchin monkeys

In primates, social context is one of the factors that increases the acceptance of novel foods. Previous experiments showed that tufted capuchins, Cebus apella, eat significantly more of novel foods when in the presence of group members eating the same novel foods. Several processes may have led to these results. The mere presence of group members may reduce the individual's stress of being alone, or its neophobic response and, consequently, may increase its food consumption. The individual may be influenced by what group members do, and local/stimulus enhancement and/or social facilitation may occur. To investigate the above processes, we assessed whether an individual capuchin monkey's consumption of novel foods is lower when (1) the individual is alone with nobody in the nearby cage than when (2) group members are present in the nearby cage with no food or when (3) they are present and eating a familiar food. We tested 15 subjects with three novel foods, each presented in one condition. In both social conditions, the more group members there were by the food box the more the experimental subject ate. In addition, when group members were present and eating food, there was a significant increase in the acceptance of the three foods, regardless of what group members were eating. We argue that social facilitation of eating is a quicker way to overcome neophobia and only social facilitation of eating what the others are eating can be considered a safe way to learn about a safe diet. Copyright 2000 The Association for the Study of Animal Behaviour.