► Delay discounting is associated with a variety of maladaptive behaviors. ► The current analyses shows that discounting for one outcome is related to discounting for other outcomes. ► These and other data suggest delay discounting may be a personality trait. Delay discounting refers to the tendency for outcomes that are remote in time to have less value than more immediate outcomes. Steep discounting of delayed outcomes is associated with a variety of social maladies. The degree of sensitivity to delayed outcomes may be a stable and pervasive individual characteristic. In analyses of archival data, the present study found positive correlations between the degree of delay discounting for one outcome (as measured by the Area Under the Curve), and the degree of discounting for other outcomes. Along with additional evidence reviewed, these data suggest that delay discounting may be considered a personality trait. Recent research in epigenetics, neuroscience, and behavior suggests delay discounting may prove to be a beneficial target for therapeutic attempts to produce global reductions in impulsivity related to delay discounting.
► We present a multi-agent model where wolf agents obey two rules to hunt a prey agent. ► The first rule is move towards the prey until a safe distance to the prey is reached. ► The second rule is when close enough to the prey, move away from the other wolves. ► These two simple rules are enough to reproduce the wolf-pack hunting ethogram. ► No communicative skills and no hierarchy are needed to complete the hunt properly. We have produced computational simulations of multi-agent systems in which wolf agents chase prey agents. We show that two simple decentralized rules controlling the movement of each wolf are enough to reproduce the main features of the wolf-pack hunting behavior: tracking the prey, carrying out the pursuit, and encircling the prey until it stops moving. The rules are (1) move towards the prey until a minimum safe distance to the prey is reached, and (2) when close enough to the prey, move away from the other wolves that are close to the safe distance to the prey. The hunting agents are autonomous, interchangeable and indistinguishable; the only information each agent needs is the position of the other agents. Our results suggest that wolf-pack hunting is an emergent collective behavior which does not necessarily rely on the presence of effective communication between the individuals participating in the hunt, and that no hierarchy is needed in the group to achieve the task properly.
In many social species, when an individual is associated with familiar conspecifics, it displays an array of behaviours that may confer benefits (e.g., increased boldness and faster habituation to novel environments). In fish, these effects of familiarity have been studied using individuals of only one sex or juveniles. Since shoals often vary regarding sex composition and males and females show different social behaviours, we hypothesised that social familiarity’s effects vary with group sex composition. We tested this hypothesis by comparing the exploratory behaviour of groups of two females, two males, and one male and one female Mediterranean killifish, , which were either familiar or unfamiliar. Pairs of familiar females were bolder than pairs of unfamiliar females, whereas males showed the opposite trend. Pairs of familiar females also showed faster habituation to the novel environment and, at the beginning of the test, were more cohesive compared to pairs of unfamiliar females. Pairs of familiar mixed-sex fish habituated faster to the novel environment than unfamiliar pairs. Pairs of familiar males did not show any beneficial effect of familiarity relative to pairs of unfamiliar males. Hence, the effects of social familiarity on exploratory behaviour, and likely the associated benefits, appear to depend on the sex composition of the pair in the Mediterranean killifish.
► Extinction of instrumental learning does not involve erasure; behavior is subject to relapse. ► Extinguished instrumental behaviors are renewed when they are tested in a new context. ► Extinguished instrumental behaviors resurge, after replacement by a second reinforced behavior, when the second behavior is extinguished. ► Extinguished instrumental behaviors can be reacquired rapidly. ► All such effects are consistent with a contextual analysis of extinction that has been developed in studies of Pavlovian extinction. It is widely recognized that extinction (the procedure in which a Pavlovian conditioned stimulus or an instrumental action is repeatedly presented without its reinforcer) weakens behavior without erasing the original learning. Most of the experiments that support this claim have focused on several “relapse” effects that occur after Pavlovian extinction, which collectively suggest that the original learning is saved through extinction. However, although such effects do occur after instrumental extinction, they have not been explored there in as much detail. This article reviews recent research in our laboratory that has investigated three relapse effects that occur after the extinction of instrumental (operant) learning. In renewal, responding returns after extinction when the behavior is tested in a different context; in resurgence, responding recovers when a second response that has been reinforced during extinction of the first is itself put on extinction; and in rapid reacquisition, extinguished responding returns rapidly when the response is reinforced again. The results provide new insights into extinction and relapse, and are consistent with principles that have been developed to explain extinction and relapse as they occur after Pavlovian conditioning. Extinction of instrumental learning, like Pavlovian learning, involves new learning that is relatively dependent on the context for expression.
This study describes delay and probability discounting patterns for hypothetical food and money in relation to percent body fat (PBF). Sixty university students completed four computerized discounting tasks in which they were asked to make a series of hypothetical decisions between (a) 10 dollars after one of several different delays (1, 2, 30, 180, and 365 days) or a smaller amount of money available immediately; (b) 10 bites of food after one of several delays (1, 2, 5, 10, and 20 h) or a smaller number of bites available immediately; (c) $10 at one of several probabilities (0.9, 0.75, 0.5, 0.25, 0.1) or a smaller amount of money to be received for sure; and (d) 10 bites of food at one of several probabilities (0.9, 0.75, 0.5, 0.25, 0.1) or a smaller number of bites to be received for sure. Median indifference points for all participants across each task were well described using the hyperbolic discounting function. Results suggest that percent body fat predicted discounting for hypothetical food, but not money, using regression analyses with the entire sample and when comparing individuals in the high and low quartiles for PBF. None of the other dietary variables (body mass index, subjective hunger, and time since last meal or snack) were related to discounting patterns. This suggests that individuals with high PBF may exhibit heightened sensitivities to delay and probability when making decisions about food.
▶ Border collie learned and retained the names of 1022 toys. ▶ She demonstrated independence of meaning of names and commands. ▶ She learned common nouns that represented categories. ▶ She learned words by inferential reasoning by exclusion. ▶ She demonstrated referential understanding of nouns. Four experiments investigated the ability of a border collie (Chaser) to acquire receptive language skills. Experiment 1 demonstrated that Chaser learned and retained, over a 3-year period of intensive training, the proper-noun names of 1022 objects. Experiment 2 presented random pair-wise combinations of three commands and three names, and demonstrated that she understood the separate meanings of proper-noun names and commands. Chaser understood that names refer to objects, independent of the behavior directed toward those objects. Experiment 3 demonstrated Chaser's ability to learn three common nouns – words that represent categories. Chaser demonstrated one-to-many (common noun) and many-to-one (multiple-name) name–object mappings. Experiment 4 demonstrated Chaser's ability to learn words by inferential reasoning by exclusion – inferring the name of an object based on its novelty among familiar objects that already had names. Together, these studies indicate that Chaser acquired referential understanding of nouns, an ability normally attributed to children, which included: (a) awareness that words may refer to objects, (b) awareness of verbal cues that map words upon the object referent, and (c) awareness that names may refer to unique objects or categories of objects, independent of the behaviors directed toward those objects.
We investigate the behavioural responses of wild type ( ) and leopard ( ) zebrafish elicited by alarm substances of conspecifics at three contexts: during the exposure period (Experiment 1); after exposure, in habituation to novelty (Experiment 2); or after exposure, in the light–dark preference test (Experiment 3), and analyse their influence on pigment response. During the exposure, showed decreased vertical drifts, increased number and duration of erratic movements, while had increased erratic movements and latency to enter the top. In the novel tank, we observed that angular velocity decreased in exposed to alarm substance, which also presented increased fear responses. Contrastingly, increased the number of entries and time in top, indicating differences in habituation profile. Alarm substance increased the number of erratic movements in the light–dark test, but elicited different responses between strains in scototaxis, latency to enter the dark compartment and risk assessment episodes. Moreover, the body colour of zebrafish did not change after alarm substance exposure. Principal component analyses suggest that burst swimming, anxiety-like behaviours, and locomotion/exploration were the components that most accounted for total variances of Experiments 1, 2, and 3, respectively. We conclude that chemical cue from conspecifics triggers strain- and context-dependent responses.
Understanding dogs’ perceptual experience of both conspecifics and humans is important to understand how dogs evolved and the nature of their relationships with humans and other dogs. Olfaction is believed to be dogs’ most powerful and perhaps important sense and an obvious place to begin for the study of social cognition of conspecifics and humans. We used fMRI in a cohort of dogs ( = 12) that had been trained to remain motionless while unsedated and unrestrained in the MRI. By presenting scents from humans and conspecifics, we aimed to identify the dimensions of dogs’ responses to salient biological odors – whether they are based on species (dog or human), familiarity, or a specific combination of factors. We focused our analysis on the dog's caudate nucleus because of its well-known association with positive expectations and because of its clearly defined anatomical location. We hypothesized that if dogs’ primary association to reward, whether it is based on food or social bonds, is to humans, then the human scents would activate the caudate more than the conspecific scents. Conversely, if the smell of conspecifics activated the caudate more than the smell of humans, dogs’ association to reward would be stronger to their fellow canines. Five scents were presented (self, familiar human, strange human, familiar dog, strange dog). While the olfactory bulb/peduncle was activated to a similar degree by all the scents, the caudate was activated maximally to the familiar human. Importantly, the scent of the familiar human was not the handler, meaning that the caudate response differentiated the scent in the absence of the person being present. The caudate activation suggested that not only did the dogs discriminate that scent from the others, they had a positive association with it. This speaks to the power of the dog's sense of smell, and it provides important clues about the importance of humans in dogs’ lives. This article is part of a Special Issue entitled: Canine Behavior.
During playful interactions, juvenile rats emit many 50-kHz ultrasonic vocalizations, which are associated with a positive affective state. In addition, these calls may also serve a communicative role – as play signals that promote playful contact. Consistent with this hypothesis, a previous study found that vocalizations are more frequent prior to playful contact than after contact is terminated. The present study uses devocalized rats to test three predictions arising from the play signals hypothesis. First, if vocalizations are used to facilitate contact, then in pairs of rats in which one is devocalized, the higher frequency of pre-contact calling should only be present when the intact rat is initiating the approach. Second, when both partners in a playing pair are devocalized, the frequency of play should be reduced and the typical pattern of playful wrestling disrupted. Finally, when given a choice to play with a vocal and a non-vocal partner, rats should prefer to play with the one able to vocalize. The second prediction was supported in that the frequency of playful interactions as well as some typical patterns of play was disrupted. Even though the data for the other two predictions did not produce the expected findings, they support the conclusion that, in rats, 50-kHz calls are likely to function to maintain a playful mood and for them to signal to one another during play fighting.
► Relation between impulsivity and timing was assessed. ► Degree of delay discounting positively correlated with mean and range of temporal bisection procedure. ► Subscales from BIS correlated with subscales from ZTPI. ► Delay discounting positively correlated with probability discounting. This study examined the relations among measures of impulsivity and timing. Impulsivity was assessed using delay and probability discounting, and self-report impulsivity (as measured by the Barratt Impulsiveness Scale; BIS-11). Timing was assessed using temporal perception as measured on a temporal bisection task and time perspective (as measured by the Zimbardo Time Perspective Inventory). One hundred and forty three college students completed these measures in a computer laboratory. The degree of delay discounting was positively correlated with the mean and range of the temporal bisection procedure. The degree of delay and probability discounting were also positively correlated. Self-reported motor impulsiveness on the BIS-11 was positively correlated with present hedonism and negatively correlated with future orientation on the ZTPI. Self-reported non-planning on the BIS-11 was positively correlated with fatalism on the ZTPI. These results show that people who overestimate the passage of time (perceive time as passing more quickly) hold less value in delayed rewards. They also confirm previous results regarding the relation between delay and probability discounting, as well as highlight similarities in self-report measures of impulsivity and time perspective.
111 Participants, recruited from Amazon's MTurk worker pool, completed monetary choice questionnaire, which involves choosing between immediate, but smaller rewards and delayed, but larger rewards. Individual participants’ responses were scored in three ways: first, by calculating the proportion of choices of the delayed rewards; second; using the scoring procedure described by to estimate discounting rate (i.e., the value of the -parameter in a hyperbolic discounting function); and third, using logistic regression to estimate discounting rate ( ). Individuals’ scores calculated using the proportion measure and the logarithms of their estimated values were very strongly correlated ( s > .97). In addition, the proportions of choices of small, medium, and large amounts of the delayed rewards were strongly correlated ( s > .80). Taken together, these results suggest that the relative ease of calculating the proportion measure does not require sacrificing reliability. Moreover, the proportion measure is atheoretical and very easy to calculate whereas estimating an individual's discounting rate requires assuming a theoretical model that may not be appropriate. Significant differences in the proportion of delayed reward choices were observed between the small, medium, and large delayed reward amounts, with smaller rewards being discounted more steeply than larger ones, replicating previous findings of magnitude effects. These results provide further validation of the proportion of delayed reward choices on the Kirby questionnaire as a measure of individual and group differences in discounting.
Phenotypic flexibility includes systems such as individual learning, social learning, and the adaptive immune system. Since the evolution of genes by natural selection is a relatively slow process, mechanisms of phenotypic flexibility are evolved to adapt to contingencies on the time scales ranging from a few hundred milliseconds (e.g. avoidance of immediate physical threats) to a few millennia (e.g. cultural adaptations to local environmental variation in the Holocene). Because environmental variation is non-stationary and fat tailed, systems of phenotypic flexibility sometimes have to be creative. They do this by means of random innovation, or exploration, and selective retention. The canonically rational way to deal with variable, uncertain environments is the Bayesian process of using new data to update priors based on past experience. Organic evolution updates the gene frequencies of populations based upon the fitness of alleles. Learning updates behavioral priors based upon the reinforcement of alternate behaviors. Genes and mechanisms of phenotypic flexibility are not isolated but richly interact. Classically, genes are said to code for the reinforcers that shape behavior in individual learning, for example. It is currently controversial whether or not these interactions include a role for the products phenotypic flexibility directly shaping selection on genes.
► -fed mice express fewer anxiety behaviors and faster complex maze run time. ► The effects of treatment in the complex maze lasted 8 weeks. ► treated mice showed more exploratory head dip behaviors in elevated zero maze. ► did not affect running wheel activity. ► Transient commensal bacteria may affect animal behavior via immunomodulatory mechanisms. Coevolution of microbes and their hosts has resulted in the formation of symbiotic relationships that enable animals to adapt to their environments and protect themselves against pathogens. Recent studies show that contact with tolerogenic microbes is important for the proper functioning of immunoregulatory circuits affecting behavior, emotionality and health. Few studies have examined the potential influence of ambient bacteria, such as on the gut–brain–microbiota axis. In this preliminary research, we show that mice fed live prior to and during a maze learning task demonstrated a reduction in anxiety-related behaviors and maze completion time, when tested at three maze difficulty levels over 12 trials for four weeks. Treated mice given in their reward completed the maze twice as fast as controls, and with reduced anxiety-related behaviors. In a consecutive set of 12 maze trials without exposure, treated mice continued to run the maze faster for the first three trials, and with fewer errors overall, suggesting a treatment persistence of about one week. Following a three-week hiatus, a final maze run revealed no differences between the experimentals and controls. Additionally, -treated mice showed more exploratory head-dip behavior in a zero maze, and treatment did not appear to affect overall activity levels as measured by activity wheel usage. Collectively, our results suggest a beneficial effect of naturally delivered, live on anxiety-related behaviors and maze performance, supporting a positive role for ambient microbes in the immunomodulation of animal behavior.
Facial expressions are routinely used to assess pain in humans, particularly those who are non-verbal. Recently, there has been an interest in developing coding systems for facial grimacing in non-human animals, such as rodents, rabbits, horses and sheep. The aims of this preliminary study were to: 1. Qualitatively identify facial feature changes in lambs experiencing pain as a result of tail-docking and compile these changes to create a Lamb Grimace Scale (LGS); 2. Determine whether human observers can use the LGS to differentiate tail-docked lambs from control lambs and differentiate lambs before and after docking; 3. Determine whether changes in facial action units of the LGS can be objectively quantified in lambs before and after docking; 4. Evaluate effects of restraint of lambs on observers’ perceptions of pain using the LGS and on quantitative measures of facial action units. By comparing images of lambs before (no pain) and after (pain) tail-docking, the LGS was devised in consultation with scientists experienced in assessing facial expression in other species. The LGS consists of five facial action units: Orbital Tightening, Mouth Features, Nose Features, Cheek Flattening and Ear Posture. The aims of the study were addressed in two experiments. In Experiment I, still images of the faces of restrained lambs were taken from video footage before and after tail-docking (n = 4) or sham tail-docking (n = 3). These images were scored by a group of five naïve human observers using the LGS. Because lambs were restrained for the duration of the experiment, Ear Posture was not scored. The scores for the images were averaged to provide one value per feature per period and then scores for the four LGS action units were averaged to give one LGS score per lamb per period. In Experiment II, still images of the faces nine lambs were taken before and after tail-docking. Stills were taken when lambs were restrained and unrestrained in each period. A different group of five human observers scored the images from Experiment II. Changes in facial action units were also quantified objectively by a researcher using image measurement software. In both experiments LGS scores were analyzed using a linear MIXED model to evaluate the effects of tail docking on observers’ perception of facial expression changes. Kendall’s Index of Concordance was used to measure reliability among observers. In Experiment I, human observers were able to use the LGS to differentiate docked lambs from control lambs. LGS scores significantly increased from before to after treatment in docked lambs but not control lambs. In Experiment II there was a significant increase in LGS scores after docking. This was coupled with changes in other validated indicators of pain after docking in the form of pain-related behaviour. Only two components, Mouth Features and Orbital Tightening, showed significant quantitative changes after docking. The direction of these changes agree with the description of these facial action units in the LGS. Restraint affected people’s perceptions of pain as well as quantitative measures of LGS components. Freely moving lambs were scored lower using the LGS over both periods and had a significantly smaller eye aperture and smaller nose and ear angles than when they were held. Agreement among observers for LGS scores were fair overall (Experiment I: W = 0.60; Experiment II: W = 0.66). This preliminary study demonstrates changes in lamb facial expression associated with pain. The results of these experiments should be interpreted with caution due to low lamb numbers.
Ayahuasca, a psychoactive beverage used by indigenous and religious groups, is generally prepared by the coction of and plants containing , -dimethyltryptamine (DMT) and β-carboline alkaloids, respectively. To investigate the acute toxicity of ayahuasca, the infusion was administered by gavage to female Wistar rats at doses of 30X and 50X the dose taken during a religious ritual, and the animals observed for 14 days. Behavioural functions were investigated one hour after dosing at 15X and 30X using the open field, elevated plus maze, and forced swimming tests. Neuronal activation (c- marked neurons) and toxicity (Fluoro-Jade B and Nissl/Cresyl staining) were investigated in the dorsal raphe nuclei (DRN), amygdaloid nucleus, and hippocampal formation brain areas of rats treated with a 30X ayahuasca dose. The actual lethal oral dose in female Wistar rats could not be determined in this study, but was shown to be higher than the 50X (which corresponds to 15.1 mg/kg bw DMT). The ayahuasca and fluoxetine treated groups showed a significant decrease in locomotion in the open field and elevated plus-maze tests compared to controls. In the forced swimming test, ayahuasca treated animals swam more than controls, a behaviour that was not significant in the fluoxetine group. Treated animals showed higher neuronal activation in all brain areas involved in serotoninergic neurotransmission. Although this led to some brain injury, no permanent damage was detected. These results suggest that ayahuasca has antidepressant properties in Wistar female at high doses, an effect that should be further investigated.
Rhythm is an important aspect of both human speech and birdsong. Adult zebra finches show increased neural activity following exposure to arrhythmic compared to rhythmic song in regions similar to the mammalian auditory association cortex and amygdala. This pattern may indicate that birds are detecting errors in the arrhythmic song relative to their learned song template or to more general expectations of song structure. Here we exposed juvenile zebra finches to natural conspecific song (rhythmic) or song with altered inter-syllable intervals (arrhythmic) prior to or during template formation, or afterward as males are matching vocal production to a memorized song template (sensorimotor integration). Before template formation, expression of the immediate early gene ZENK was increased in the caudomedial nidopallium (NCM) of birds exposed to rhythmic relative to arrhythmic song. During template formation, ZENK expression was increased in the caudomedial mesopallium (CMM) of birds exposed to arrhythmic relative to rhythmic song. These results suggest that the youngest birds may be predisposed to respond to a more natural stimulus, and a template may be required for arrhythmic song to elicit increased neural activity. It also appears that functional development across the brain regions investigated continues to maturity.
Prolonged aversive response of zebrafish after a single CAS exposure. The cartoon shows the changes on basal preference of zebrafish observed after different postconditioning sessions (DPC1, DPC2, DPC3, and DPC7) using a CPA paradigm. Blue arrows indicate the time spent in white and yellow compartments at preconditioning and postconditioning phases (10-min trial) after introducing fish into a central gray partition (green arrows). The behavioral phenotypes observed in CPA apparatus (high- and low-avoider fish) are shown. Anxiety, trauma- and stressor-related disorders are severe psychiatric conditions that affect human population worldwide. Given their genetic tractability, evolutionarily conserved neurotransmitter systems, and extensive behavioral repertoire, zebrafish have become an emergent model organism in translational neuroscience. Here, we investigate whether a single exposure to conspecific alarm substance (CAS) produces fear conditioning in zebrafish using a conditioned place aversion (CPA) paradigm, as well as the persistence of aversive responses at different time intervals. While CAS elicited freezing and erratic movements at conditioning phase, zebrafish showed a robust avoidance for the CAS-paired compartment and increased risk assessment up to 7 days postconditioning. Additionally, we observed the existence of two behavioral phenotypes (high- and low-avoider fish) that present different fear-like responses at conditioning phase and evasion of the conditioning side at postconditioning trials. Collectively, we show a prolonged conditioned place aversion in zebrafish after a single CAS conditioning session, reinforcing the use of fear conditioning protocols as valuable strategies for modeling psychiatric disorders-related phenotypes in zebrafish.
Delay discounting is the tendency to prefer smaller, sooner rewards to larger, later ones. Poor adherence in type 2 diabetes could be partially explained by a discounted value of health, as a function of delay. Delay discounting can be described with a hyperbolic model characterized by a coefficient, k. The higher k, the less future consequences are taken into account when making decisions. This study aimed to determine whether k would be correlated with glycated hemoglobin and adherence in type 2 diabetes. Ninety-three patients were recruited in two diabetology departments. Delay discounting coefficients were measured with a computerized task. HbA1c was recorded and adherence was assessed by questionnaires. Potential socio-demographic and clinical confounding factors were collected. There was a positive correlation between delay discounting of gains and HbA1c (r = 0.242, P = 0.023). This association remained significant after adjusting for potential confounding factors (F = 4.807, P = 0.031, η = 0.058). This association was partially mediated by adherence to medication (β = 0.048, 95% CI [0.004–0.131]). Glycemic control is associated with delay discounting in patients suffering from type 2 diabetes. Should these findings be replicated with a prospective design, they could lead to new strategies to improve glycemic control among these patients.
Human-induced alterations of ecosystems and environmental conditions often lead to changes in the geographical range of plants and animals. While modelling exercises may contribute to understanding such dynamics at large spatial scales, they rarely offer insights into the mechanisms that prompt the process at a local scale. Savi’s pipistrelle ( ) is a vespertilionid bat widespread throughout the Mediterranean region. The species’ recent range expansion towards northeastern Europe is thought to be induced by urbanization, yet no study actually tested this hypothesis, and climate change is a potential alternative driver. In this radio-telemetry study, set in the Vesuvius National Park (Campania region, Southern Italy) we provide insights into the species’ thermal physiology and foraging ecology and investigate their relationships with potential large-scale responses to climate, and land use changes. Specifically, we test whether i) exploits urbanisation by selecting urban areas for roosting and foraging, and ii) tolerates heatwaves (a proxy for thermophily) through a plastic use of thermoregulation. Tolerance to heatwaves would be consistent with the observation that the species’ geographic range is not shifting but expanding northwards. Tracked bats roosted mainly in buildings but avoided urban habitats while foraging, actively selecting non-intensive farmland and natural wooded areas. showed tolerance to heat, reaching the highest body temperature ever recorded for a free-ranging bat (46.5 °C), and performing long periods of overheating. We conclude that is not a strictly synurbic species because it exploits urban areas mainly for roosting, and avoids them for foraging: this questions the role of synurbization as a range expansion driver. On the other hand, the species’ extreme heat tolerance and plastic thermoregulatory behaviour represent winning traits to cope with heatwaves typical of climate change-related weather fluctuations.