Parasitic egg rejection decisions of chalk-browed mockingbirds <Emphasis Type="Italic">Mimus saturninus</Emphasis> are independent of clutch composition

Obligate avian brood parasites lay their eggs in nests of other host species, which assume all the costs of parental care for the foreign eggs and chicks. The most common defensive response to parasitism is the rejection of foreign eggs by hosts. Different cognitive mechanisms and decision-making rules may guide both egg recognition and rejection behaviors. Classical optimization models generally assume that decisions are based on the absolute properties of the options (i.e., absolute valuation). Increasing evidence shows instead that hosts’ rejection decisions also depend on the context in which options are presented (i.e., context-dependent valuation). Here we study whether the chalk-browed mockingbird’s (Mimus saturninus) rejection of parasitic shiny cowbird (Molothrus bonariensis) eggs is a fixed behavior or varies with the context of the clutch. We tested three possible context-dependent mechanisms: (1) range effect, (2) habituation to variation, and (3) sensitization to variation. We found that mockingbird rejection of parasitic eggs does not change according to the characteristics of the other eggs in the nest. Thus, rejection decisions may exclusively depend on the objective characteristics of the eggs, meaning that the threshold of acceptance or rejection of a foreign egg is context-independent in this system.     

Anuran predators overcome visual illusion: dazzle coloration does not protect moving prey

Predators everywhere impose strong selection pressures on the morphology and behavior of their prey, but the resulting antipredator adaptations vary greatly among species. Studies of adaptive coloration in prey species have generally focused on cryptic or aposematic prey, with little consideration of color patterns in palatable mobile prey. Complex color patterns have been proposed to decrease the ability of visual predators to capture moving prey (motion dazzle effect). Most support for this hypothesis, however, comes from experiments with human subjects and simulated prey. We tested the motion dazzle effect using, for the first time, natural predators (cane toads, Rhinella marina) and live prey (house crickets, Acheta domesticus) with altered color patterns. We found no support for the motion dazzle effect as striped crickets did not fare better than solid colored ones. Crickets that spent more time moving, however, were more likely to be eaten. Our results suggest that motion specialized visual predators such as toads overcome the motion dazzle effect and impose stronger selection pressure on prey behavior than on coloration. These findings emphasize the importance of sensory specializations of predators in mediating antipredator strategies.     

The eyes have it: lateralized coping strategies in cattle herds responding to human approach

We report a range of lateralized coping strategies adopted by large social groups of cattle in response to mild challenges posed by humans of varying degrees of familiarity. At either 14 or 18 pens at a commercial feedlot, with 90 to 200 cattle in each, we conducted a series of video recorded ‘pressure tests’. ‘Frontal’ pressure tests involved walking from a position perpendicular to the concrete feed bunk of a given pen, towards the geometric centre of the line of feeding cattle. ‘Bunk-side’ pressure tests involved experimenters walking closely past a pen of feeding cattle in one direction, before returning in the opposite direction shortly afterwards. Experimenters wore white dust masks to alter their facial features in the bunk-side pressure tests. In both frontal and bunk-side pressure tests, distance from the experimenter influenced cattle’s choice of binocular viewing, cessation of feeding, standing or stepping backwards to monitor the approach and leaving the feed bunk. The frequency of these coping strategies differed in a lateralized manner. The cattle were more likely to accept the close positioning of a generally familiar, unmasked human on their left, which is traditionally referred to as the “near” side. By contrast, when responding to the approach of an unfamiliar, masked human, cattle conformed to the general vertebrate model and were more likely to remove themselves from the potential threat viewed within the left and not right visual field. We argue that the traditional terms for livestock sidedness as “near” (left) and “off” (right) sides demonstrate a knowledge of behavioural lateralization in domestic livestock that has existed for over 300 years of stock handling.     

Individual identity and affective valence in marmoset calls: in vivo brain imaging with vocal sound playback

As with humans, vocal communication is an important social tool for nonhuman primates. Common marmosets (Callithrix jacchus) often produce whistle-like ‘phee’ calls when they are visually separated from conspecifics. The neural processes specific to phee call perception, however, are largely unknown, despite the possibility that these processes involve social information. Here, we examined behavioral and whole-brain mapping evidence regarding the detection of individual conspecific phee calls using an audio playback procedure. Phee calls evoked sound exploratory responses when the caller changed, indicating that marmosets can discriminate between caller identities. Positron emission tomography with [¹⁸F] fluorodeoxyglucose revealed that perception of phee calls from a single subject was associated with activity in the dorsolateral prefrontal, medial prefrontal, orbitofrontal cortices, and the amygdala. These findings suggest that these regions are implicated in cognitive and affective processing of salient social information. However, phee calls from multiple subjects induced brain activation in only some of these regions, such as the dorsolateral prefrontal cortex. We also found distinctive brain deactivation and functional connectivity associated with phee call perception depending on the caller change. According to changes in pupillary size, phee calls from a single subject induced a higher arousal level compared with those from multiple subjects. These results suggest that marmoset phee calls convey information about individual identity and affective valence depending on the consistency or variability of the caller. Based on the flexible perception of the call based on individual recognition, humans and marmosets may share some neural mechanisms underlying conspecific vocal perception.     

Tool-use training temporarily enhances cognitive performance in long-tailed macaques (<Emphasis Type="Italic">Macaca fascicularis</Emphasis>)

Tool use relies on numerous cognitive functions, including sustained attention and understanding of causality. In this study, we investigated the effects of tool-use training on cognitive performance in primates. Specifically, we applied the Primate Cognition Test Battery to three long-tailed macaques (Macaca fascicularis) at different stages of a training procedure that consisted of using a rake to retrieve out-of-reach food items. In addition, we evaluated a control group (n?=?3) performing a grasping task, in order to account for possible effects related to a simple motor act. Our results showed that tool-use training enhances mean performance in the physical cognition domain, i.e. the understanding of spatial relations, numerosity and causality. In particular, causal cognition (evaluating noise- and shape-related causality and understanding of tool properties) showed significant improvement after training, whereas spatial cognition (evaluating spatial memory, object permanence, rotation and transposition) showed a trend to improvement. Despite these findings, none of our trained monkeys succeeded in the tool-use task of the Primate Cognition Test Battery, which involved an unfamiliar tool. Some training-related effects did not persist after a 35-day resting period, suggesting that continuous practice may be necessary, or that a longer training period before resting may be needed to better maintain cognitive performance. In contrast with the training group, the control group did not display any change in cognitive performance. This finding paves the way to further investigation into the link between tool-use behaviour and the evolution of primate cognition.     

Interspecies transmission of emotional information via chemosignals: from humans to dogs (<Emphasis Type="Italic">Canis lupus familiaris</Emphasis>)

We report a study examining interspecies emotion transfer via body odors (chemosignals). Do human body odors (chemosignals) produced under emotional conditions of happiness and fear provide information that is detectable by pet dogs (Labrador and Golden retrievers)? The odor samples were collected from the axilla of male donors not involved in the main experiment. The experimental setup involved the co-presence of the dog’s owner, a stranger and the odor dispenser in a space where the dogs could move freely. There were three odor conditions [fear, happiness, and control (no sweat)] to which the dogs were assigned randomly. The dependent variables were the relevant behaviors of the dogs (e.g., approaching, interacting and gazing) directed to the three targets (owner, stranger, sweat dispenser) aside from the dogs’ stress and heart rate indicators. The results indicated with high accuracy that the dogs manifested the predicted behaviors in the three conditions. There were fewer and shorter owner directed behaviors and more stranger directed behaviors when they were in the “happy odor condition” compared to the fear odor and control conditions. In the fear odor condition, they displayed more stressful behaviors. The heart rate data in the control and happy conditions were significantly lower than in the fear condition. Our findings suggest that interspecies emotional communication is facilitated by chemosignals.     

Positive Mental Health as a Predictor of Problematic Internet and Facebook Use in Adolescents and Young Adults

Recent research on Problematic Internet Use and Problematic Facebook Use (PIU and PFU) has focused on the idea that people who engage in PIU or PFU are more likely to present with mental health problems. The goal of the present study was to examine the contribution of positive mental health (PMH) to PIU and PFU among adolescents and young adults. A total of 1927 Italian adolescents and young adults participated in the study. Structural equation modeling showed that PMH is negatively linked to both PIU and PFU, indicating that PMH may be an important antecedent for both PIU and PFU among adolescents and young adults. In conclusion, dimensions of PMH may be taken into account by researchers and educational practitioners in preventing both PIU and PFU.     

Life Satisfaction and Economic Position Relative to Neighbors: Perceptions Versus Reality

I examine the relationship between economic position relative to local neighbors and life satisfaction in rural Bangladesh. In particular, I exploit a novel household level census of three villages that includes the geospatial coordinates of every household and a perception measure of economic position relative to neighbors. This allows for exploring the sensitivity of the aforementioned relationship to (1) different objective definitions of neighborhood, and (2) the type of positional measure used, objective or perceived. I find that a higher perceived position improves life satisfaction while objective position has no statistically significant effect. This difference stems from a very low correlation between the objective and perceived positional measures. The low correlation can be explained by individual specific heterogeneity in definitions of neighbor. However, observable socioeconomic and demographic variables cannot explain the difference.     

Young macaques (<Emphasis Type="Italic">Macaca fascicularis</Emphasis>) preferentially bias attention towards closer,older, and better tool users

Examining how animals direct social learning during skill acquisition under natural conditions, generates data for examining hypotheses regarding how transmission biases influence cultural change in animal populations. We studied a population of macaques on Koram Island, Thailand, and examined model-based biases during interactions by unskilled individuals with tool-using group members. We first compared the prevalence of interactions (watching, obtaining food, object exploration) and proximity to tool users during interactions, in developing individuals (infants, juveniles) versus mature non-learners (adolescents, adults), to provide evidence that developing individuals are actively seeking information about tool use from social partners. All infants and juveniles, but only 49% of mature individuals carried out interacted with tool users. Macaques predominantly obtained food by scrounging or stealing, suggesting maximizing scrounging opportunities motivates interactions with tool users. However, while interactions by adults was limited to obtaining food, young macaques and particularly infants also watched tool users and explored objects, indicating additional interest in tool use itself. We then ran matrix correlations to identify interaction biases, and what attributes of tool users influenced these. Biases correlated with social affiliation, but macaques also preferentially targeted tool users that potentially increase scrounging and learning opportunities. Results suggest that social structure may constrain social learning, but the motivation to bias interactions towards tool users to maximize feeding opportunities may also socially modulate learning by facilitating close proximity to better tool users, and further interest in tool-use actions and materials, especially during development.