An ecological framework of neophobia: from cells to organisms to populations

The "Seven Deadly Sins" of Neophobia Experimental Design

Neophobia, an aversive response to novelty, is a behavior with critical ecological and evolutionary relevance for wild populations because it directly influences animals' ability to adapt to new environments and exploit novel resources. Neophobia has been described in a wide variety of different animal species from arachnids to zebra finches. Because of this widespread prevalence and ecological importance, the number of neophobia studies has continued to increase over time. However, many neophobia studies (as well as many animal behavior studies more generally) suffer from one or more of what we have deemed the "seven deadly sins" of neophobia experimental design. These "sins" include: (1) animals that are not habituated to the testing environment, (2) problems with novel stimulus selection, (3) non-standardized motivation, (4) pseudoreplication, (5) lack of sufficient controls, (6) fixed treatment order, and (7) using arbitrary thresholds for data analysis. We discuss each of these potential issues in turn and make recommendations for how to avoid them in future behavior research. More consistency in how neophobia studies are designed would facilitate comparisons across different populations and species and allow researchers to better understand whether neophobia can help explain animals' responses to human-altered landscapes and the ability to survive in the Anthropocene.

Exploring the Importance of Environmental Complexity for Newly Hatched Zebrafish

The effects of an early impoverished social or physical environment on vertebrate neural development and cognition has been known for decades. While existing studies have focused on the long-term effects, measuring adult cognitive phenotypes, studies on the effects of environmental complexity on the early stages of development are lacking. Zebrafish (Danio rerio) hatchlings are assumed to have minimal interaction with their environment and are routinely reared in small, bare containers. To investigate the effects of being raised under such conditions on development of behaviour and cognition, hatchlings housed for 10 days in either an enriched or a standard environment underwent two cognitive tasks. The results were mixed. Subjects of the two treatments did not differ in performance when required to discriminate two areas. Conversely, we found a significant effect in a number discrimination task, with subjects from impoverished condition performing significantly worse. In both experiments, larvae reared in impoverished environment showed a reduced locomotor activity. Given the effects that enrichment appears to exert on larvae, a third experiment explored whether hatchlings exhibit a spontaneous preference for more complex environments. When offered a choice between a bare setting and one with objects of different shapes and colors, larvae spent over 70% of time in the enriched sector. Deepening these effects of an early impoverished environment on cognitive development is crucial for the welfare of captive zebrafish populations and for enhancing the quality and reliability of studies on larval zebrafish.

Uncertainty about predation risk: a conceptual review

Uncertainty has long been of interest to economists and psychologists and has more recently gained attention among ecologists. In the ecological world, animals must regularly make decisions related to finding resources and avoiding threats. Here, we describe uncertainty as a perceptual phenomenon of decision-makers, and we focus specifically on the functional ecology of such uncertainty regarding predation risk. Like all uncertainty, uncertainty about predation risk reflects informational limitations. When cues are available, they may be novel (i.e. unknown information), incomplete, unreliable, overly abundant and complex, or conflicting. We review recent studies that have used these informational limitations to induce uncertainty of predation risk. These studies have typically used either over-responses to novelty (i.e. neophobia) or memory attenuation as proxies for measuring uncertainty. Because changes in the environment, particularly unpredictable changes, drive informational limitations, we describe studies assessing unpredictable variance in spatio-temporal predation risk, intensity of predation risk, predator encounter rate, and predator diversity. We also highlight anthropogenic changes within habitats that are likely to have dramatic impacts on information availability and thus uncertainty in antipredator decisions in the modern world.

Curiosity-driven exploration: foundations in neuroscience and computational modeling

Curiosity refers to the intrinsic desire of humans and animals to explore the unknown, even when there is no apparent reason to do so. Thus far, no single, widely accepted definition or framework for curiosity has emerged, but there is growing consensus that curious behavior is not goal-directed but related to seeking or reacting to information. In this review, we take a phenomenological approach and group behavioral and neurophysiological studies which meet these criteria into three categories according to the type of information seeking observed. We then review recent computational models of curiosity from the field of machine learning and discuss how they enable integrating different types of information seeking into one theoretical framework. Combinations of behavioral and neurophysiological studies along with computational modeling will be instrumental in demystifying the notion of curiosity.

Child characteristic correlates of food rejection in preschool children: A narrative review

Dietary habits formed in early childhood are key for establishing a healthy diet later in life. Picky eating and food neophobia - the two main forms of food rejection in young children - form an important barricade to establishing such healthy habits. Understanding these types of food rejection is thus essential for promoting healthy eating behaviour in both children and adults. To this end, the present narrative review aims to provide an overview of food rejection research in preschool-aged children, focusing on recent advances in the cognitive literature. Specifically, we evaluate the link between children's cognitive development, chemosensory perception and affective evaluation of food, food knowledge, decision-making strategies, anxiety and disgust sensitivity, and food rejection behaviour. Longitudinal and experimental studies are necessary to establish how the relationships between food rejection and cognitive processes develop over time and to determine their causal directions.

Microhabitat conditions drive uncertainty of risk and shape neophobic responses in Trinidadian guppies, Poecilia reticulata

In response to uncertain risks, prey may rely on neophobic phenotypes to reduce the costs associated with the lack of information regarding local conditions. Neophobia has been shown to be driven by information reliability, ambient risk and predator diversity, all of which shape uncertainty of risk. We similarly expect environmental conditions to shape uncertainty by interfering with information availability. In order to test how environmental variables might shape neophobic responses in Trinidadian guppies (Poecilia reticulata), we conducted an in situ field experiment of two high-predation risk guppy populations designed to determine how the 'average' and 'variance' of several environmental factors might influence the neophobic response to novel predator models and/or novel foraging patches. Our results suggest neophobia is shaped by water velocity, microhabitat complexity, pool width and depth, as well as substrate diversity and heterogeneity. Moreover, we found differential effects of the 'average' and 'variance' environmental variables on food- and predator-related neophobia. Our study highlights that assessment of neophobic drivers should consider predation risk, various microhabitat conditions and neophobia being tested. Neophobic phenotypes are expected to increase the probability of prey survival and reproductive success (i.e. fitness), and are therefore likely linked to population health and species survival. Understanding the drivers and consequences of uncertainty of risk is an increasingly pressing issue, as ecological uncertainty increases with the combined effects of climate change, anthropogenic disturbances and invasive species.

Exploration of A Novel Environment is Not Correlated With Object Neophobia in Wild-caught House Sparrows (Passer domesticus)

Novel object, food, and environment trials have been widely used to understand how individual variation in neophobia (an aversion to novelty) relates to variation in endocrine, physiological, and ecological traits. However, what is often missing from these studies is an evaluation of whether an animal's response to one type of neophobia test is reflective of its response to other neophobia tests. In this study we investigated whether spatial neophobia was significantly correlated with responses to a novel object paradigm. In spatial neophobia trials, wild-caught house sparrows (n = 23) were allowed access to a novel environment (an adjacent cage with familiar objects placed in new locations). Time to first enter and total time spent in the novel environment were assessed. In novel object trials, birds were exposed to a new novel object in, on, or near their food dish and time to approach and feed from the dish was measured. Results indicate that neither time spent in a novel environment nor time to first enter a novel environment were correlated with an individual's average response to novel object trials. Therefore, these two tests may be assessing two discrete behaviors that involve separate decision-making processes and functional circuits in the brain.

Integrating sensory ecology and predator-prey theory to understand animal responses to fire

Fire regimes are changing dramatically worldwide due to climate change, habitat conversion, and the suppression of Indigenous landscape management. Although there has been extensive work on plant responses to fire, including their adaptations to withstand fire and long-term effects of fire on plant communities, less is known about animal responses to fire. Ecologists lack a conceptual framework for understanding behavioural responses to fire, which can hinder wildlife conservation and management. Here, we integrate cue-response sensory ecology and predator-prey theory to predict and explain variation in if, when and how animals react to approaching fire. Inspired by the literature on prey responses to predation risk, this framework considers both fire-naïve and fire-adapted animals and follows three key steps: vigilance, cue detection and response. We draw from theory on vigilance tradeoffs, signal detection, speed-accuracy tradeoffs, fear generalization, neophobia and adaptive dispersal. We discuss how evolutionary history with fire, but also other selective pressures, such as predation risk, should influence animal behavioural responses to fire. We conclude by providing guidance for empiricists and outlining potential conservation applications.

Conceptualization, context, and comparison are key to understanding the evolution of fear

The fearful ape hypothesis proposes that heightened fearfulness in humans is adaptive. However, despite its attractive anthropocentric narrative, the evidence presented for greater fearfulness in humans versus other apes is not sufficient to support this claim. Conceptualization, context, and comparison are strongly lacking in Grossmann's proposal, but are key to understanding variation in the fear response among individuals and species.

Fear generalization and behavioral responses to multiple dangers

Animals often exhibit consistent-individual differences (CIDs) in boldness/fearfulness, typically studied in the context of predation risk. We focus here on fear generalization, where fear of one danger (e.g., predators) is correlated with fear of other dangers (e.g., humans, pathogens, moving vehicles, or fire). We discuss why fear generalization should be ecologically important, and why we expect fear to correlate across disparate dangers. CIDs in fear are well studied for some dangers in some taxa (e.g., human fear of pathogens), but not well studied for most dangers. Fear of some dangers has been found to correlate with general fearfulness, but some cases where we might expect correlated fears (e.g., between fear of humans, familiar predators, and exotic predators) are surprisingly understudied.

Poor conceptual knowledge in the food domain and food rejection dispositions in 3- to 7-year-old children

Previous research established that children with poorer taxonomic knowledge in the food domain display increased levels of food rejection. However, the food domain heavily lends itself to script and thematic conceptual knowledge (e.g., pancakes at breakfast), to which young children already attend. This series of studies investigated the development of conceptual knowledge, specifically in the food domain, and the link with food rejection. Study 1 used a nonconflicting triad task testing children's knowledge of four subtypes of script and thematic associations (food-food pairs, food-utensil pairs, event scripts, and meal scripts) with children aged 3-6 years living in the United States (18 males and 14 females). Study 2 employed the same design along with a measure of food rejection in 3- to 6-year-olds living in France (67 males and 62 females). There was significant conceptual development in both groups, but thematic food concepts are acquired earlier than meal script concepts. Study 3 investigated the link between thematic and script cross-classification and food rejection in 39 females and 33 males living in France (4- to 7-year-olds). Results demonstrate that children as young as 3 years old are already attending to thematic and script structures to inform food-based decision making. Even more critically, Study 3 showed that increased food rejection tendencies are negatively related to script and thematic understanding in the food domain. Such seminal studies illustrate the importance of conceptual knowledge in children's interpretation and acceptance of food, highlighting promising avenues for knowledge-based interventions to foster dietary variety.

The effect of target-related and target-irrelevant novel stimuli on response behaviour

Novel events catch our attention, which can influence performance of a task. Whether this attentional capture by novelty benefits or impairs performance depends on several factors, such as the relevance of the stimulus, task requirements, and the timing of the event. Additionally, it has been argued that novel stimuli can hold intrinsic reward value, which may directly affect approach motivation, similar to positive valence stimuli. This link between novelty and approach/avoid behaviour has not been investigated directly. Here, we investigated whether stimulus novelty interacts with response behaviour in an approach/avoidance task, and whether these effects depend on the task relevance of novelty and stimulus timing. In experiment 1, participants gave an approach or avoid response dependent on a shape (diamond or square) presented at different stimulus onset asynchronies (SOA) following a novel or familiar scene (target-irrelevant novelty). In experiment 2, participants had to approach or avoid a novel or familiar image depending on the content (indoor/outdoor; target-related novelty). A shape was presented at different SOA. Results of a linear mixed model showed novelty-induced performance costs as demonstrated by longer RT and lower accuracy when novelty was target-relevant, likely due to attentional lingering at novel images. When images were target-irrelevant, approach but not avoid responses were faster for familiar versus novel images at 200 ms SOA only. Thus, novelty had a differentially pronounced detrimental effect on performance. These observations confirm that processing of novel stimuli generally depends on stimulus relevance, and tentatively suggests that differential processing of novel and familiar images is intensified by motivated approach behaviour.

Fear of the new? Geckos hesitate to attack novel prey, feed near objects and enter a novel space

Neophobia, the fear of novelty, is an ecologically important response which enables animals to avoid potentially harmful situations. Neophobia is a cognitive process by which individuals distinguish novelty from familiarity. In this study, we aimed to quantify this cognitive process in captive tokay geckos (Gekko gecko) across three contexts: when encountering novel prey, foraging near novel objects and entering a novel space. We also investigated individual consistency across trials using different novel stimuli, and correlation of individual responses across the three contexts. We found that geckos hesitate to attack novel prey and prey close to objects (familiar and novel). Geckos hesitated the most when entering novel space. Repeatability of behaviour within and across contexts was low (R = 0.101-0.190) indicating that neophobia might not be expressed similarly across contexts. The strength of a neophobic response can indicate how anxious or curious an individual is. This test has great potential to help answer questions about how captivity, enrichment, rearing environment and cognition affect fear responses in different contexts in lizards. By studying reptiles, we can better understand the universality of what is known about the causes leading to difference in neophobia across individuals and species.

Tears for pears: Influence of children’s neophobia on categorization performance and strategy in the food domain

Preschoolers’ neophobic dispositions mainly target fruits and vegetables. They received a great deal of attention in the past decades as these dispositions represent the main psychological barrier to dietary variety. Recently, children’s food neophobia has been found to be negatively correlated with their categorization performance (i.e., the accuracy to discriminate between food categories). We investigated categorization strategies among neophobic children, tendencies to favor one type of error over the other (misses over false alarms), in order to compensate for their poor categorization performance. To capture children’s categorization strategies, we used the Signal Detection Theory framework. A first experiment assessed 120 3-to-6-years old children’ sensitivity to discriminate between foods and nonfoods as well as their decision criterion (i.e., response strategy). In a second experiment, we manipulated the influence of food processing. The hypothesis was that food processing acts as a sign of human interventions that decreases uncertainty about edibility and thus promotes feelings of safety in the food domain. 137 children were tested on a food versus nonfood categorization task contrasting whole and sliced stimuli. In both experiments, increased levels of food neophobia were significantly associated with poorer categorization sensitivity and with a more conservative decision criterion (i.e., favoring “it is inedible” errors). Additionally, results from Experiment 2 revealed that food processing did not influence neophobic children, whereas their neophilic counterparts adopted a more liberal decision criterion for sliced stimuli than for whole stimuli. These findings are the first demonstration of a relationship between a decision criterion and food neophobia in young children. These results have strong implications for theories of food neophobia and laid the groundwork for designing novel types of food education interventions.

Constitutive gene expression differs in three brain regions important for cognition in neophobic and non-neophobic house sparrows (Passer domesticus)

Neophobia (aversion to new objects, food, and environments) is a personality trait that affects the ability of wildlife to adapt to new challenges and opportunities. Despite the ubiquity and importance of this trait, the molecular mechanisms underlying repeatable individual differences in neophobia in wild animals are poorly understood. We evaluated wild-caught house sparrows (Passer domesticus) for neophobia in the lab using novel object tests. We then selected a subset of neophobic and non-neophobic individuals (n = 3 of each, all females) and extracted RNA from four brain regions involved in learning, memory, threat perception, and executive function: striatum, caudal dorsomedial hippocampus, medial ventral arcopallium, and caudolateral nidopallium (NCL). Our analysis of differentially expressed genes (DEGs) used 11,889 gene regions annotated in the house sparrow reference genome for which we had an average of 25.7 million mapped reads/sample. PERMANOVA identified significant effects of brain region, phenotype (neophobic vs. non-neophobic), and a brain region by phenotype interaction. Comparing neophobic and non-neophobic birds revealed constitutive differences in DEGs in three of the four brain regions examined: hippocampus (12% of the transcriptome significantly differentially expressed), striatum (4%) and NCL (3%). DEGs included important known neuroendocrine mediators of learning, memory, executive function, and anxiety behavior, including serotonin receptor 5A, dopamine receptors 1, 2 and 5 (downregulated in neophobic birds), and estrogen receptor beta (upregulated in neophobic birds). These results suggest that some of the behavioral differences between phenotypes may be due to underlying gene expression differences in the brain. The large number of DEGs in neophobic and non-neophobic birds also implies that there are major differences in neural function between the two phenotypes that could affect a wide variety of behavioral traits beyond neophobia.

Individual Variation in Response to Novel Food in Captive Capuchin Monkeys (Sapajus spp.)

How animals respond to novelty may have important outcomes in terms of fitness. On the one hand, aversion to novel stimuli may reduce the risks of consuming potentially toxic food or encountering predators. On the other hand, the propensity to approach novel stimuli may allow individuals to explore novel food sources and more flexibly adapt to novel challenges. Different species and individuals may find different ways to balance the costs and benefits that novelty posits. To date, however, little is known on how response to novel food varies across individuals of the same species depending on their previous experience with novelty, risk attitude and presence of higher-ranking conspecifics. In this study, we assessed individual variation in response to novel food by testing captive capuchin monkeys (Sapajus spp.) in an unconstrained social context, where all individuals in a group were able to access the testing area on a voluntary basis. We provided familiar and novel food to 23 study subjects belonging to four social groups differing in (i) previous experience with novel food, (ii) risk attitude (as assessed by a previous risky decision-making task), and (iii) dominance rank. We predicted that, as individuals may generalize their previous experience to novel contexts, those with more previous experience with novel food would be less neophobic than those with less experience. Moreover, if neophobia is a facet of the individual’s risk attitude, we predicted that more risk-prone individuals would be less neophobic than less risk-prone ones. Finally, individuals might flexibly modify their food choices according to the presence of conspecifics; in this respect, we predicted that, in response to monopolization of preferred resources by higher-ranking individuals, lower-ranking individuals would prefer familiar over novel food in the absence of higher-ranking individuals, but would modify their preference in favor of novel food in the presence of higher-ranking individuals. None of these predictions were supported by our results. We observed, however, that neophobia, measured as the latency to retrieve a food item, was more pronounced in lower-ranking than higher-ranking individuals, and that males showed a generally stronger bias than females toward a quicker retrieval of familiar food.

Disturbance cues function as a background risk cue but not as an associative learning cue in tadpoles

Chemical information has an important role in the sensory ecology of aquatic species. For aquatic prey, chemical cues are a vital source of information related to predator avoidance and risk assessment. For instance, alarm cues are released by prey that have been injured by predators. In addition to providing accurate information about current risk, repeated exposure to alarm cues can elicit a fear response to novel stimuli (neophobia) in prey. Another source of chemical information is disturbance cues, released by prey that have been disturbed or harassed (but not injured) by a predator. While disturbance cues have received much less attention than alarm cues, they appear to be useful as an early warning signal of predation risk and have the potential to be used as a priming cue for learning. In this study, we used wood frog (Lithobates sylvaticus) tadpoles to test whether repeated exposure to disturbance cues during the embryonic stage can induce neophobic behaviour. Three weeks following repeated exposure to disturbance cues, tadpoles showed reduced activity when exposed to a novel odour, but they no longer displayed an antipredator response to disturbance cues. In a second experiment, we found that tadpoles failed to learn that a novel odour was dangerous following a pairing with disturbance cues, whereas alarm cues facilitated such learning. Our results add to the growing body of information about disturbance cues and provide evidence of their function as an embryonic risk cue but not as an associative learning cue.

Innate visual discrimination abilities of zebrafish larvae

The ability to discriminate between objects visually plays a key role in animals' interactions with their environment because it enables them to recognise companions, prey, and predators. In the zebrafish, Danio rerio, hatching occurs early on during development (48-72 h post fertilisation), and the larvae must forage and evade predators despite their immature sensory and cognitive systems. Using a preference paradigm, we investigated whether larval zebrafish are nonetheless capable of discriminating between visual stimuli. We found that larvae discriminated not only between figures with different colours or different shapes, but also between two identical figures with different orientations and between sets of figures with different numerosities. By manipulating larvae's exposure to objects before the test, we demonstrated that their discrimination abilities are innate and do not depend upon experience. This study highlighted that zebrafish possess relatively sophisticated visual discrimination abilities even at the larval stage. These abilities likely improve larval survival via the recognition of biologically relevant stimuli.

Exploratory decisions of Trinidadian guppies when uncertain about predation risk

Animals can reduce their uncertainty of predation risk by gathering new information via exploration behaviour. However, a decision to explore may also be costly due to increased predator exposure. Here, we found contextual effects of predation risk on the exploratory activity of Trinidadian guppies Poecilia reticulata in a novel environment. First, guppies were exposed to a 3-day period of either high or low background predation risk in the form of repeated exposure to either injured conspecific cues (i.e. alarm cues) or control water, respectively. A day later, guppies were moved into a testing arena with limited visual information due to structural barriers and were then presented with an acute chemical stimulus, either alarm cues (a known and reliable indicator of risk), a novel odour (an ambiguous cue), or control water. In the presence of control water, guppies from high and low background risk showed a similar willingness to explore the arena. However, high-risk individuals significantly reduced their spatial evenness, although not their movement latency, in the presence of both the alarm and novel cues. When these high-risk individuals were a member of a shoal, they became willing to explore the environment more evenly in the presence of alarm cues while remaining cautious toward the novel cue, indicating an effect of the greater uncertainty associated with the novel cue. In contrast, low-risk guppies showed a willingness to explore the arena regardless of acute threat or social context. Such contextual effects of background risk and social context highlight the complexity of exploratory decisions when uncertain.

Cross-Context Responses to Novelty in Rural and Urban Small Mammals

The Anthropocene is the era of urbanization. The accelerating expansion of cities occurs at the expense of natural reservoirs of biodiversity and presents animals with challenges for which their evolutionary past might not have prepared them. Cognitive and behavioral adjustments to novelty could promote animals’ persistence under these altered conditions. We investigated the structure of, and covariance between, different aspects of responses to novelty in rural and urban small mammals of two non-commensal rodent species. We ran replicated experiments testing responses to three novelty types (object, food, or space) of 47 individual common voles (Microtus arvalis) and 41 individual striped field mice (Apodemus agrarius). We found partial support for the hypothesis that responses to novelty are structured, clustering (i) speed of responses, (ii) intensity of responses, and (iii) responses to food into separate dimensions. Rural and urban small mammals did not differ in most responses to novelty, suggesting that urban habitats do not reduce neophobia in these species. Further studies investigating whether comparable response patters are found throughout different stages of colonization, and along synurbanization processes of different duration, will help illuminate the dynamics of animals’ cognitive adjustments to urban life.

Predation risk shapes the use of conflicting personal risk and social safety information in guppies

When faced with uncertainty, animals can benefit from using multiple sources of information in order to make an optimal decision. However, information sources (e.g., social and personal cues) may conflict, while also varying in acquisition cost and reliability. Here, we assessed behavioral decisions of Trinidadian guppies (Poecilia reticulata), in situ, when presented with conflicting social and personal information about predation risk. We positioned foraging arenas within high- and low-predation streams, where guppies were exposed to a personal cue in the form of conspecific alarm cues (a known indicator of risk), a novel cue, or a control. At the same time, a conspecific shoal (a social safety cue) was either present or absent. When social safety was absent, guppies in both populations showed typical avoidance responses towards alarm cues, and high-predation guppies showed their typical avoidance of novel cues (i.e., neophobia). However, the presence of social safety cues was persuasive, overriding the neophobia of high-predation guppies and emboldening low-predation guppies to ignore alarm cues. Our experiment is one of the first to empirically assess the use of safety and risk cues in prey and suggests a threshold level of ambient risk which dictates the use of conflicting social and personal information.

Strength or Nausea? Children's Reasoning About the Health Consequences of Food Consumption

Children’s reasoning on food properties and health relationships can contribute to healthier food choices. Food properties can either be positive (“gives strength”) or negative (“gives nausea”). One of the main challenges in public health is to foster children’s dietary variety, which contributes to a normal and healthy development. To face this challenge, it is essential to investigate how children generalize these positive and negative properties to other foods, including familiar and unfamiliar ones. In the present experiment, we hypothesized that children might rely on cues of food processing (e.g., signs of human intervention such as slicing) to convey information about item edibility. Furthermore, capitalizing on previous results showing that food rejections (i.e., food neophobia and picky eating) are a significant source of inter-individual variability to children’s inferences in the food domain, we followed an individual approach. We expected that children would generalize the positive properties to familiar foods and, in contrast, that they would generalize more often the negative properties to unfamiliar foods. However, we expected that children would generalize more positive and less negative properties to unfamiliar sliced foods than to whole unfamiliar foods. Finally, we expected that children displaying higher levels of food rejections would generalize more negative properties than children displaying lower levels of food rejections. One-hundred and twenty-six children, aged 3–6 years, performed an induction task in which they had to generalize positive or negative health-related properties to familiar or unfamiliar foods, whole or sliced. We measured children’s probability of generalization for positive and negative properties. The children’s food rejection score was assessed on a standardized scale. Results indicated that children evaluated positively familiar foods (regardless of processing), whereas they tend to view unfamiliar food negatively. In contrast, children were at chance for processed unfamiliar foods. Furthermore, children displaying higher levels of food rejections were more likely to generalize the negative properties to all kinds of foods than children displaying lower levels of food rejections. These findings entitle us to hypothesize that knowledge-based food education programs should take into account the valence of the properties taught to children, as well as the state of processing of the food presented. Furthermore, one should take children’s interindividual differences into account because they influence how the knowledge gained through these programs may be generalized.

Disturbance cue communication is shaped by emitter diet and receiver background risk in Trinidadian guppies

In animal communication systems, individuals that detect a cue (i.e., “receivers”) are often influenced by characteristics of the cue emitter. For instance, in many species, receivers avoid chemical cues that are released by emitters experiencing disturbance. These chemical “disturbance cues” appear to benefit receivers by warning them about nearby danger, such as a predator’s approach. While the active ingredients in disturbance cues have been largely unexplored, by-products of metabolized protein are thought to play a role for some species. If so, the content (quality) and volume (quantity) of the emitter’s diet should affect their disturbance cues, thus altering how receivers perceive the cues and respond. Guppies Poecilia reticulata are a species known to discriminate among disturbance cues from different types of donors, but dietary variation has yet to be explored. In this study, we found evidence that diet quality and quantity can affect disturbance cues released by guppy emitters (i.e., experimental “donors”). Receivers discriminated between donor cue treatments, responding more strongly to cues from donors fed a protein-rich bloodworm diet (Experiment 1), as well as an overall larger diet (Experiment 2). We also found that receivers exposed to higher background risk were more sensitive to disturbance cue variation, with the strongest avoidance responses displayed by high-risk receivers toward disturbance cues from donors fed the high-quality diet. Therefore, diet, and perhaps protein specifically, affects either the concentration or composition of disturbance cues released by guppies. Such variation may be important in information signaling in social species like the guppy.

Mismatch Between Risk and Response May Amplify Lethal and Non-lethal Effects of Humans on Wild Animal Populations

Human activity has rapidly transformed the planet, leading to declines of animal populations around the world through a range of direct and indirect pathways. Humans have strong numerical effects on wild animal populations, as highly efficient hunters and through unintentional impacts of human activity and development. Human disturbance also induces costly non-lethal effects by changing the behavior of risk-averse animals. Here, we suggest that the unique strength of these lethal and non-lethal effects is amplified by mismatches between the nature of risk associated with anthropogenic stimuli and the corresponding response by wild animals. We discuss the unique characteristics of cues associated with anthropogenic stimuli in the context of animal ecology and evolutionary history to explore why and when animals fail to appropriately (a) detect, (b) assess, and (c) respond to both benign and lethal stimuli. We then explore the costs of over-response to a benign stimulus (Type I error) and under-response to a lethal stimulus (Type II error), which can scale up to affect individual fitness and ultimately drive population dynamics and shape ecological interactions. Finally, we highlight avenues for future research and discuss conservation measures that can better align animal perception and response with risk to mitigate unintended consequences of human disturbance.

Strawberries and Cream: The Relationship Between Food Rejection and Thematic Knowledge of Food in Young Children

Establishing healthy dietary habits in childhood is crucial in preventing long-term repercussions, as a lack of dietary variety in childhood leads to enduring impacts on both physical and cognitive health. Poor conceptual knowledge about food has recently been shown to be a driving factor of food rejection. The majority of studies that have investigated the development of food knowledge along with food rejection have mainly focused on one subtype of conceptual knowledge about food, namely taxonomic categories (e.g., vegetables or meat). However, taxonomic categorization is not the only way to understand the food domain. We also heavily rely on other conceptual structures, namely thematic associations, in which objects are grouped because they share spatial-temporal properties or exhibit a complementary relationship (e.g., soft-boiled egg and soldiers). We rely on such thematic associations between food items, which may not fall into the same taxon, to determine the acceptability of food combinations. However, the development of children's ability to master these relations has not been systematically investigated, nor alongside the phenomenon of food rejection. The present research aims to fill this gap by investigating (i) the development of conceptual food knowledge (both taxonomic and thematic) and (ii) the putative relationship between children's food rejection (as measured by the Child Food Rejection Scale) and both thematic and taxonomic food knowledge. A proportional (A:B::C:?) analogy task, with a choice between taxonomic (i.e., bread and pasta) and thematic (i.e., bread and butter) food associates, was conducted on children between 3 and 7-years-old (n = 85). The children were systematically presented with either a thematic or taxonomic food base pair (A:B) and then asked to extend the example type of relation to select the respective thematic or taxonomic match to the target (C:?). Our results revealed, for the first time, that increased levels of food rejection were significantly predictive of poorer food identification and decreased thematic understanding. These findings entitle us to hypothesize that knowledge-based food education programs to foster dietary variety in young children, should not only aim to improve taxonomic understanding of food, but also thematic relations.

Traffic noise inhibits cognitive performance in a songbird

Noise pollution is commonly associated with human environments and mounting evidence indicates that noise has a variety of negative effects on wildlife. Noise has also been linked to cognitive impairment in humans and because many animals use cognitively intensive processes to overcome environmental challenges, noise pollution has the potential to interfere with cognitive function in animals living in urban areas or near roads. We experimentally examined how road traffic noise impacts avian cognitive performance by testing adult zebra finches (Taeniopygia guttata) on a battery of foraging tasks in the presence or absence of traffic noise playback. Here, we show that traffic noise reduces cognitive performance, including inhibitory control, motor learning, spatial memory and social learning, but not associative colour learning. This study demonstrates a novel mechanism through which anthropogenic noise can impact animals, namely through cognitive interference, and suggests that noise pollution may have previously unconsidered consequences for animals.

Neophobia in 10 ungulate species-a comparative approach

ABSTRACT

Neophobia (the fearful reaction to novel stimuli or situations) has a crucial effect on individual fitness and can vary within and across species. However, the factors predicting this variation are still unclear. In this study, we assessed whether individual characteristics (rank, social integration, sex) and species socio-ecological characteristics (dietary breadth, group size, domestication) predicted variation in neophobia. For this purpose, we conducted behavioral observations and experimental tests on 78 captive individuals belonging to 10 different ungulate species-an ideal taxon to study inter-specific variation in neophobia given their variety in socio-ecological characteristics. Individuals were tested in their social groups by providing them with familiar food, half of which had been positioned close to a novel object. We monitored the individual latency to approach and eat food and the proportion of time spent in its proximity. Using a phylogenetic approach and social network analyses, we showed that across ungulate species neophobia was higher in socially more integrated individuals, as compared to less integrated ones. In contrast, rank and sex did not predict inter-individual differences in neophobia. Moreover, species differed in their levels of neophobia, with Barbary sheep being on average less neophobic than all the other study species. As group size in Barbary sheep was larger than in all the other study species, these results support the hypothesis that larger group size predicts lower levels of neophobia, and confirm ungulates as a highly promising taxon to study animal behavior and cognition with a comparative perspective.

SIGNIFICANCE STATEMENT

In several species, individuals may respond fearfully to novel stimuli, therefore reducing the risks they may face. However, it is yet unclear if certain individuals or species respond more fearfully to novelty. Here, we provided food to 78 individual ungulates with different characteristics (e.g., sex, rank, social integration, group size, domestication, dietary breadth) in different controlled conditions (e.g., when food was close to novel or to familiar objects). Across species, we found that socially integrated individuals responded more fearfully in all species. Moreover, being in larger groups decreased the probability of fearfully responding to novelty.

SUPPLEMENTARY INFORMATION

The online version contains supplementary material available at 10.1007/s00265-021-03041-0.

Chronic stress reverses enhanced neophobia following an acute stressor in European starlings

Neophobia is an animal's avoidance of novelty. Animals tend to respond to novel objects by increasing their latency to approach the objects, and they eventually habituate after repeated exposure by attenuating this increased approach latency. Interestingly, the physiological stress response does not appear to have a causal link to neophobia, although acute stress can prevent animals from habituating to novel objects, possibly through a permissive effect. Chronic stress can induce an anxiety-like state in animals, while often disrupting the ability to respond to acute stress. We thus hypothesized that chronic stress may increase neophobia and tested this by inducing chronic stress in wild-caught European starlings (Sturnus vulgaris). Four distinct anthropogenic stressors were administered daily for 30 min each in a randomized order for 21 days. We then evaluated whether exposure to chronic stress altered the latency to approach a novel object placed on or near a food dish presented after overnight fasting. Chronically stressed birds and nonstressed controls exhibited similar initial neophobic responses to novel objects and showed similar habituation in response to repeated exposure. However, when birds were exposed to 15 min of restraint before repeated exposure to the same object, habituation was eliminated in control birds (i.e., they continued to respond with neophobia), whereas chronically stressed birds continued to show habituation as measured by attenuated approach latencies. These results demonstrate that an acute stress response (restraint) has a different impact on neophobia depending upon whether the bird is or is not concurrently exposed to chronic stress.

Differential impact of shorter and longer periods of environmental enrichment on adult zebrafish exploratory activity (Danio rerio) in the novel tank paradigm

Several studies have used zebrafish to investigate the effects of environmental enrichment on behavior and physiology. However, to date there are no studies evaluating the behavioral responses, such as habituation and exploration, of enriched-housed zebrafish when they are submitted to novelty paradigms. The present work was, therefore, designed to evaluate the habituation and exploratory responses of zebrafish exposed to enriched- (EE) and non-enriched (NE) environments when they face novelty. Adult wild-type zebrafish were used. Three different enriched contexts were designed. In Context 1, zebrafish was exposed to enrichment during 7 days, which reduced their total distance traveled in novel tank and social preference tests in comparison to the non-enriched animals. In Context 2, animals were exposed to same enrichment during 14 days. EE exposure did not alter the behavioral responses of zebrafish compared to NE. In Context 3, fish were exposed to enrichment during 14 days, with changing the enriching elements at day 8. Similarly to Context 1, total distance traveled was reduced by EE exposure when compared to NE. Our results suggest a modulatory effect of EE on adult zebrafish locomotion that may be dependent on the time of exposure and on the physical structure of the enriched environment.

Early-life and parental predation risk shape fear acquisition in adult minnows

Exposure to predation risk can induce a fearful baseline state, as well as fear reactions toward novel situations (i.e., neophobia). Some research indicates that risk exposure during sensitive periods makes adults more prone to acquiring long-term fearful phenotypes. However, chronic risk can also lead to ignoring threats in order to maintain other activities. We sought to assess how a relatively long period of low risk, experienced either early in life or by the previous generation, influences fear behaviour acquired from a short period of high risk as adults. We used fathead minnows as study subjects and simulated predation risk with repeated exposures to conspecific chemical alarm cues. The period of high risk experienced by adults induced typical fear behaviour (baseline freezing and neophobia), whereas the early-life low-risk period 1 year prior caused only a reduction in baseline foraging. We found no evidence that the early-life risk significantly altered the fear acquired from the adult-risk period. However, in a second experiment, a low-risk period during the parental generation interacted with a high-risk period experienced by the adult offspring. The combination of both risk periods heightened baseline freezing despite parental risk having little effect independently. Hence, our study provides evidence that parental risk exposure can lead to an additive intergenerational effect on fear acquisition in minnows.

The propensity for re-triggered predation fear in a prey fish

Variation in predation risk can drive variation in fear intensity, the length of fear retention, and whether fear returns after waning. Using Trinidadian guppies, we assessed whether a low-level predation threat could easily re-trigger fear after waning. First, we show that background risk induced neophobia after either multiple exposures to a low-level threat or a single exposure to a high-level threat. However, a single exposure to the low-level threat had no such effect. The individuals that received multiple background exposures to the low-level threat retained their neophobic phenotype over an 8-day post-risk period, and this response was intensified by a single re-exposure to the low-level threat on day 7. In contrast, the neophobia following the single high-level threat waned over the 8-day period, but the single re-exposure to the low-level threat on day 7 re-triggered the neophobic phenotype. Thus, despite the single low-level exposure being insufficient to induce neophobia, it significantly elevated existing fear and re-triggered fear that had waned. We highlight how such patterns of fear acquisition, retention, and rapid re-triggering play an important role in animal ecology and evolution and outline parallels between the neophobic phenotype in fishes and dimensions of post-traumatic stress in humans.

Temporally variable predation risk and fear retention in Trinidadian guppies

Predation fear is a unifying theme across vertebrate taxa. Here, we explored how the frequency and duration of predation risk affects postrisk fear behavior in Trinidadian guppies. We first exposed individuals to visual cues of potential predators for 3 days, either frequently (6×/day) or infrequently (1×/day). Each exposure lasted for either a relatively brief (5 min) or long (30 min) duration, whereas a control group consisted of no risk exposures. One day later, we quantified guppy behavior. All background risk treatments induced a fear response toward a novel odor (i.e., neophobia), and individuals previously exposed to frequent bouts of brief risk showed elevated baseline fear. Although neophobic responses were initially similar across risk treatments (1 day later), retention of this response differed. After 8 days, only individuals previously exposed to brief bouts of risk (both frequent and infrequent) maintained neophobic responses, whereas their initially higher level of baseline fear remained elevated but was no longer significantly different from the control. These results increase our understanding of temporal factors that affect the intensity and retention of fear that persists after risk exposure, which may have applications across vertebrates in relation to problems with fearful phenotypes.