Behavioural processes
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Tag-based ethnocentric cooperation is a highly robust behavior which can evolve and prevail under a wide variety of conditions. Recent studies have demonstrated, however, that ethnocentrism can temporarily be suppressed by other competing strategies, especially in its early evolutionary stages. In a series of computational experiments, conducted with an agent-based evolutionary model of tag-mediated cooperation, we addressed the question of whether a stochastically established and once dominant non-ethnocentric strategy such as indiscriminate altruism can stably persist and permanently outweigh ethnocentrism. ⋯ We find that in combination with an implemented memory mechanism and tags, random bias acting in favor of altruists can lead to their long-lasting victory over all other types of strategists. The difference in density between altruistic and ethnocentric cooperators increases with greater rewiring of the underlying network, but decreases with growing population size. These findings suggest that randomness plays an important role in promoting non-ethnocentric cooperation and contributes to our understanding of how other than adaptive mechanisms can initiate the design of novel behavioral phenotypes, thereby shaping surprisingly new evolutionary pathways.
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Behavioural processes · Feb 2015
Acquisition of operant behavior in rats with delayed reinforcement: A retractable-lever procedure.
Experimentally naïve rats acquired lever pressing with delayed reinforcement when the immediate programmed consequence for lever pressing was the simultaneous retraction of two identical levers. Presses on one lever also produced access to sweetened condensed milk after a delay of 10s following retraction. Presses on the second lever resulted in retraction only. ⋯ Responding for seven out of eight rats decreased during a subsequent extinction phase in which retraction was the only consequence arranged for lever pressing. Responding recovered rapidly when food reinforcement was available again. Furthermore, when contingencies on the two levers were switched, rats allocated their behavior accordingly, showing control by the delayed reinforcers.
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Behavioural processes · Jan 2015
Scent of the familiar: an fMRI study of canine brain responses to familiar and unfamiliar human and dog odors.
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 (N=12) that had been trained to remain motionless while unsedated and unrestrained in the MRI. ⋯ 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.
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Behavioural processes · Mar 2014
Estrogen-dependent effects on behavior, lipid-profile, and glycemic index of ovariectomized rats subjected to chronic restraint stress.
Stress has been shown to negatively affect the immune system, alter the body's metabolism, and play a strong role in the development of mood disorders. These effects are mainly driven through the release of hormones from the hypothalamic-pituitary-adrenal axis (HPA). Additionally, women are more likely to be affected by stress due to the estrogen fluctuation associated with their menstrual cycle. ⋯ In addition, stress reduces glucose and TC levels. Moreover, stress increase TG levels in the presence of E2 and decrease in its absence, as well as the estradiol increase TG levels in stressed groups and reduced in non-stressed groups. Our data suggest an important interaction between stress and estrogen, showing that hormonal status can induce changes in the animal's response to stress.
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Behavioural processes · Sep 2013
Consummatory suppression due to incentive downshift is not a consequence of enhanced search behavior.
Rats shifted from 32% to 4% sucrose solution consume less from the 4% solution than rats that experience only the 4% solution. This consummatory suppression, a phenomenon known as consummatory successive negative contrast (cSNC), is accompanied by an increase in other behaviors such as rearing, nose-down locomotion, ambulation, sampling new sources and grooming. Despite a large body of studies on the cSNC, it remains to be determined whether reduced consumption is part of the direct response to the reward downshift or a byproduct of the increase in alternative competing behaviors. ⋯ Rats were trained either with 32% or 4% sucrose solution for ten days in restrainers that limited almost all movement. On the next five days, all subjects received the 4% sucrose solution and a robust suppression in drinking in the downshifted animals was observed. These results suggest that consummatory suppression is a direct consequence of incentive downshift and not a byproduct of the increase in competing behaviors.