Behavioural Processes最新文献

Two experiments compared the reinforcing effects of sucrose and maltose across a range of concentrations. The results were interpreted using the Multiplicative Hyperbolic Model of reinforcer value (MHM). In Experiment 1, rats were exposed to a discrete-trials schedule in which they chose between the test compound (sucrose or maltose) and a standard sucrose solution (0.4 M, delivered after a 4-s delay). Percentage choice of each test compound increased as a function of concentration. The maximum percentage choice of maltose was significantly less than that of sucrose; the concentration corresponding to the half-maximal selection of the test compound was lower for maltose than for sucrose. In Experiment 2 the preference function for sucrose alone was compared with the preference function for a sucrose solution to which a fixed concentration of maltose had been added. The presence of maltose elevated the function and shifted it leftwards (i.e. towards lower concentrations). The results were interpreted in terms of MHM using two alterntive models ‘borrowed’ from classical pharmacological receptor theory. It was concluded that maltose and sucrose are not fully substitutable reinforcers and that the reinforcing effect of maltose may be mediated by an action at more than one species of sweet taste receptor.

Pairing a palatable flavor (US) with an initially neutral flavor cue (CS) results in an acquired conditioned preference for the latter. Two main associations have been proposed to explain the acquisition of flavor preferences: Flavor-Flavor and Flavor-Nutrient learning. Although the hedonic reaction triggered by US consumption has also been suggested as a possible additional component underlying acquired flavor preference, this issue has received little attention. Here we explored whether the amount of training to the CS-US compound can favor the formation of a Flavor-Hedonic reaction association using rats as subjects and sucrose as the US. We expected that the more exposure to the CS-US compound, the stronger the S-R type association. Since S-R associations are not sensitive to devaluation procedures, we used a Sensory-Specific Satiety procedure to devalue the US after conditioning and then measured preferences for the CS. On Experiment 1 with a short restrictive training (classic procedure), preference for the CS was decreased after devaluation of the US compared to the control condition. On Experiment 2, with short unrestrictive training, preference for the CS was again weakened. Experiment 3 with a long unrestrictive training, rats expressed preference for the CS regardless of the devaluation procedure. These results suggest that, as with an instrumental paradigm, extensive training in flavor preference learning undermines the US devaluation effect.

Exaggerated sexual traits, such as ornaments and courtship displays, are crucial for mate acquisition in many species and are often subject to directional runaway selection. However, in the face of high predation risk, natural selection can result in a reduction of conspicuous precopulatory displays to avoid detection by potential predators. Sexual selection may then favour increased investment in inconspicuous postcopulatory traits. Here, we investigated the transgenerational effects of predation on precopulatory male courtship and postcopulatory sexual traits (testes size, sperm length) in a dung fly, Sepsis punctum (Sepsidae). Behavioural assays prior to selection document a marked decrease in male courtship displays in the presence of a predator, the Asian Ant Mantis (Odontomantis planiceps). However, after ten generations of experimental evolution, flies exhibited a marked increase in courtship, both in the absence and presence of a predator. Additionally, under sustained predation pressure, male and female body size decreased but male postcopulatory traits were not significantly affected. These results suggest that precopulatory courtship can be under strong sexual selection even in the face of predation pressure. Larger flies were more susceptible to predation, and there could be canalisation of postcopulatory traits that are crucial for fertilisation.

In many biparental mammals, such as California mice (Peromyscus californicus), fathers display affiliative behavior toward unfamiliar infants whereas reproductively naïve adult males show highly variable responses. Sources of this variability are not well understood, but evidence suggests that stress can either enhance or inhibit alloparental care. We evaluated immediate and delayed effects of acute stress on pup-directed behavior in adult virgin male California mice. Mice underwent three 10-minute tests with unfamiliar pups at 48-hour intervals. Stressed mice (N=22) received a subcutaneous oil injection immediately before tests 1 and 2, whereas controls (N=22) were left undisturbed. In controls, but not stressed mice, latency to approach the pup decreased and duration of alloparental behavior increased across the three tests. At each time point, stressed males were less likely than controls to perform alloparental behavior. Controls spent significantly more time performing alloparental behavior than stressed mice in tests 1 and 2 but not in test 3. Pup-directed aggression did not differ between the groups at any time point. These findings suggest that acute stress can both inhibit alloparental behavior in the short term and prevent the increase in alloparental behavior that typically occurs with repeated exposure to pups in virgin male California mice.

Individual animals exhibit considerable differences in cognitive characteristics associated with personality differences. The cognition-personality link was intensively investigated in the last decade though with mixed results. To grasp the general pattern, a common method should be applied to a wide range of animals. We tested novel object recognition (NOR) in the mourning gecko (Lepidodactylus lugubris) and investigated whether boldness, assessed in an anti-predator context, explained neophobia and how much attention animals pay to their surroundings. Boldness did not simply explain object neophobia but predicted attention to novel objects. Specifically, shy geckos showed shorter latency to approach the novel object than bold geckos only in the changed situation in which distinct types of objects were presented in two successive phases. However, no significant effect of boldness was detected in the unchanged situation in which the same object was presented twice. Our findings suggest that, in the mourning gecko, (1) boldness and object neophobia represent different aspects of personality traits and that (2) boldness underlies sensitivity to slight changes in the environment.

Prey-predator interactions have resulted in the evolution of many anti-predatory traits. One of them is the ability for prey to listen to predators and avoid them. Although prey anti-predatory behavioural responses to predator auditory cues are well described in a wide range of taxa, studies on whether butterflies change their behaviours in response to their predatory calls are lacking. Heliconius butterflies are unpalatable and form Müllerian mimicry rings as morphological defence strategies against their avian predators. Like many other butterflies in the Nymphalidae family, some Heliconius butterflies possess auditory organs, which are hypothesized to assist with predator detection. Here we test whether Heliconius melpomene change their behaviour in response to their predatory bird calls by observing the behaviour of male and female H. m. plessini exposed to calls of Heliconius avian predators: rufous-tailed jacamar, migratory Eastern kingbird, and resident tropical kingbird. We also exposed them to the calls of the toco toucan, a frugivorous bird as a control bird call, and an amplified greenhouse background noise as a noise control. We found that individuals changed their behaviour in response to jacamar calls only. Males increased their walking and fluttering behaviour, while females did not change their behaviour during the playback of the jacamar call. Intersexual behaviours like courtship, copulation, and abdomen lifting did not change in response to bird calls. Our findings suggest that despite having primary predatory defences like toxicity and being in a mimicry ring, H. m. plessini butterflies changed their behaviour in response to predator calls. Furthermore, this response was predator specific, as H. m. plesseni did not respond to either the Eastern kingbird or the tropical kingbird calls. This suggests that Heliconius butterflies may be able to differentiate predatory calls, and potentially the birds associated with those calls.

Instrumental appetitive extinction involves the reduction of a previously reinforced response when its occurrence is no longer rewarded. Two experiments with terrestrial toads (Rhinella arenarum) tested whether the occurrence of a nonreinforced response is necessary for response extinction by varying the time of exposure to nonrewarded goal-box stimuli across groups. In Experiment 1, toads that received the same acquisition training (15 sessions, 1 session/day, 300 s of access to water in the goal box) were randomly assigned to two groups. In Group 600 (n=12), animals spent 600 s in the goal box in 8 daily extinction sessions (water present but inaccessible). In Group 0 (n=11), toads performed the runway response (i.e., walking from the start to the goal box) but were removed as soon as they entered the goal box, thus having minimal exposure to nonrewarded goal-box stimuli. The runway response was weakened in Group 600 across extinction trials, but exhibited little change in Group 0. In Experiment 2, toads were randomly assigned to two groups after the same acquisition training. Group 0 (n=7) was treated the same as Group 0 in the previous experiment. In Group RI (retention interval, n=7), toads remained in their home cage for 13 days. Finally, all animals received 4 extinction sessions with 300 s in the empty goal box. There was little behavioral change in Group 0 during the 13 sessions with minimal exposure to the goal box. In extinction, both groups reduced their runway response at similar rates. Although the procedures were instrumental, extinction of the runway response in toads can be accounted for in terms of a Pavlovian approach response to stimuli paired with reward and nonreward in the goal box.

Fetal programming by subnutrition affects offspring’s behaviour, metabolism, and sensitivity to stressors in sheep. The objective was to determine the stress response of ewes born to mothers nutritionally restricted during gestation to social isolation followed by exposure to a novel object. Twenty-six-year-old Corriedale ewes born to mothers who grazed high or low pasture allowances (HPA and LPA groups) from 23 days before conception until 122 days of gestation were used. Ewes were individually isolated in a novel place for 10 min, and 5 min after its beginning, an orange ball was dropped into the test pen. The ewes’ behaviours were recorded during the test. Blood proteins, glucose and cortisol concentrations, heart and respiratory rates and rectal and surface temperatures were determined. The number of times looking at the ball tended to be greater in HPA ewes than LPA (6.7 ± 1.0 vs 4.7 ± 0.8, P = 0.08). The LPA ewes had greater serum albumin concentration than HPA ewes (3.2 ± 0.1 g/dL vs 3.0 ± 0.1 g/dL, P = 0.02), regardless of the applied stressors. Overall, the nutritional treatments applied to ewes during their intrauterine development did not modify the stress responses to social isolation followed by exposure to a novel object.

Spontaneously Hypertensive Rats (SHR) have been extensively studied as an animal model of Attention Deficit Hyperactivity Disorder (ADHD) because they show some of the defining features of that disorder, like some forms of impulsivity and hyperactivity. However, other characteristics of the disorder, like a deficit in motivation, have been scarcely studied in the SHR strain. In the present report, we studied in 45 SHR and 45 Wistar rats as a comparison group, the capacity of attribution of incentive salience to a stimulus predictor of reinforcement, which has become a central concept in the study of motivation. We employed the Pavlovian Conditioned-Approach (PCA) task, in which a lever is presented 8 s before a pellet is delivered. The attribution of incentive salience is indicated by responses to the lever, in contrast to the absence of attribution of incentive salience, which is indicated by entrances to the pellet receptacle. For quantifying the attribution of incentive salience, we employed the PCA index, which integrates three related variables for each type of response, lever presses and entrances to the feeder: 1) the number of responses, 2) the latency to the first response, and 3) the probability that at least one response occurred during the presence of the lever. SHR showed lower levels of PCA, suggesting a deficit in the attribution of incentive salience to the lever. This finding replicates the results reported by previous research that compared SHR’s performance in the PCA task against that of Sprague-Dawley rats.

Understanding how animal collectives and societies form and function is a fundamental goal in animal biology. To date, research examining fish shoaling behavior has focused mostly on the general principles and ecological relevance of the phenomeon, while the ways in which physiological state (e.g., nutrition) affects collective behavior remain overlooked. Here, we investigated the shoaling behavior of common minnows (Phoxinus phoxinus) with three different nutritional states (control treatment: fasting for 24 h, fasting treatment: fasting for 7 days, and digestion treatment: 1 h after satiation feeding) across two ecological contexts (i.e., without and with food). No effects of either nutritional state or context were found on swimming speed, but the acceleration was greater in the digestion group than in the control group, with that in the fasting group being intermediate. Similar to change tendency in group length and group width of shoals, both interindividual distance and nearest neighbor distance were also greater in the fasting group than in the digestion group, suggesting that fasting and digestion may exert opposite driving forces on group cohesion. However, neither nutritional state nor context influenced the group area, group speed, group percent time moving, or group polarization. Both the foraging efficiency and the percentage of food items consumed by the fish shoals were greater in the fasting and control groups than in the digestion group. Our study suggested that one week of hunger and the energetically demanding stage of food digestion tend to have opposite influences on group shape, while the social foraging context does not influence the individual and group behavior of fish.