We consider interacting urns on a finite directed network, where both sampling and reinforcement processes depend on the nodes of the network. This extends previous research by incorporating node-dependent sampling and reinforcement. We classify the sampling and reinforcement schemes, as well as the networks on which the proportion of balls of either colour in each urn converges almost surely to a deterministic limit. We also investigate conditions for achieving synchronisation of the colour proportions across the urns and analyse fluctuations under specific conditions on the reinforcement scheme and network structure.

Operant procedures occupy a prominent role within animal welfare science because they provide information about the strength of animals’ preferences. It is assumed that strongly motivated choices commonly indicate conditions necessary for uncompromised welfare. A review of the literature shows that members of many species will work for access to resources not commonly provided to them; including a secure resting place (perches for hens or boxes for rodents) and substrates for species-typical activities such as nesting, digging and rooting (in hens, rats, mice and pigs). Despite a recent surge in popularity, operant techniques remain under-utilised and studies employing them struggle to find the best method for prioritising resources. In order to fully exploit the potential of operant procedures a wider appreciation of the relevant theories and techniques might be beneficial; including greater employment of the basic principles of reinforcement theory and further development of more complex economic analogies. If these two strands of research develop together, operant approaches have a key role to play in refining and replacing husbandry practices that undermine animal welfare.

Twenty horses were paired for age, sex and breed and placed into one of two groups. The horses in Group A (control) were reinforced using only negative reinforcement (NR) while those in group B (treatment) were reinforced with both positive reinforcement (PR) and NR concurrently. All horses were shaped for the halt response while being driven in long-reins over a period of 5 consecutive days. On day I, all horses were given a baseline test of 20 random halts while being long-reined in an indoor arena. On days 2-4, the shaping of the halt response continued with horses being reinforced according to the group to which they had been allocated. On day 5 of testing the baseline test was repeated (final test). During the baseline and final tests, behavioural responses and accuracy of completion of the halt response were recorded. Heart rates were recorded continuously during testing. One-way analysis of variance in randomised blocks and analysis of covariance using baseline data as a covariate showed no effect on latency to halt. However, horses reinforced with both NR and PR shook their heads vertically less and were more likely to lick their lips than those reinforced with NR only. There was also a trend for an increase in roundness of outline of the horses that were reinforced with both PR and NR. These results suggest that the implementation of PR effectively into equitation training may improve the welfare of the horse.

We introduce a general two-colour interacting urn model on a finite directed graph, where each urn at a node reinforces all the urns in its out-neighbours according to a fixed, non-negative, and balanced reinforcement matrix. We show that the fraction of balls of either colour converges almost surely to a deterministic limit if either the reinforcement is not of Pólya type or the graph is such that every vertex with non-zero in-degree can be reached from some vertex with zero in-degree. We also obtain joint central limit theorems with appropriate scalings. Furthermore, in the remaining case when there are no vertices with zero in-degree and the reinforcement is of Pólya type, we restrict our analysis to a regular graph and show that the fraction of balls of either colour converges almost surely to a finite random limit, which is the same across all the urns.

We consider a model of N interacting two-colour Friedman urns. The interaction model considered is such that the reinforcement of each urn depends on the fraction of balls of a particular colour in that urn as well as the overall fraction of balls of that colour in all the urns combined together. We show that the urns synchronize almost surely and that the fraction of balls of each colour converges to the deterministic limit of one-half, which matches with the limit known for a single Friedman urn. Furthermore, we use the notion of stable convergence to obtain limit theorems for fluctuations around the synchronization limit.

Magnolia sinica, a Critically Endangered tree endemic to Yunnan, China, is one of the 20 plant species with extremely small populations approved by the Yunnan government for urgent rescue action before 2015. Information on the geographical distribution and population size of this species had not previously been reported, hindering effective conservation. We therefore carried out a survey of the literature and of herbarium specimens, followed by a detailed field survey and morphological measurements and observations of surviving individuals. We located 52 individuals in the wild, in eight localities. Two distinguishing morphological characters (tepal colour and tepal number) were revised based on observations of all remaining wild individuals that produced flowers and on one 30-year-old flowering plant in Kunming Botanical Garden. The survival rate of individuals propagated from seed for ex situ conservation at the Garden was 100% over 5 years; of 100 individuals transplanted to each of two reinforcement sites, 20 and 18, respectively, were alive after 6 years. We propose two groups of measures to protect M. sinica: (1) in situ conservation, population monitoring, and public engagement, and (2) ex situ conservation with reinforcement or reintroduction.

In 1957, Skinner, in his “Verbal Behavior”, proposed an explanation on how a language is learned. In 1959, Chomsky strongly argued the non-learnability of language, establishing in the field of developmental psycholinguistics the substitution of the term “learning” for that of “acquisition”. Currently, the constructivist models describe language acquisition as a process of ontogenetic, gradual, complex, and adaptive change. This new theoretical framework has been especially useful for rereading Verbal Behavior because it facilitates recovering the Skinnerian learning mechanisms. This can be observed in the recent research trends that recapture reinforcement and imitation (echoic responses), although they are now located in the initial phases of the process and are included in a cognitive dynamic that, by gradually increasing its complexity, can achieve grammar. The new constructivist theoretical framework, by retrieving the functional and referential aspects of language, can also take advantage of the classic Skinnerian proposal about the pragmatic types of verbal behavior, providing it with new meaning.

Psychostimulants, including amphetamine (AMPH), exert robust arousal-enhancing, reinforcing and locomotor-activating effects. These behavioural actions involve drug-induced elevations in extracellular norepinephrine (NE) and dopamine (DA) within a variety of cortical and subcortical regions. The lateral hypothalamic area (LHA), including the lateral hypothalamus proper, perifornical area and adjacent dorsomedial hypothalamus, is implicated in appetitive- and arousal-related processes. The LHA is innervated by both NE and DA projections and systemically administered AMPH has been demonstrated to activate LHA neurons. Combined, these and other observations suggest the LHA may be a site of action in the behavioural effects of psychostimulants. To test this hypothesis, we examined the degree to which AMPH (10 nmol, 25 nmol) acts within the LHA to exert arousing, locomotor-activating and reinforcing actions in quietly resting/sleeping rats. Although intra-LHA AMPH robustly increased time spent awake, this occurred in the absence of pronounced locomotor activation or reinforcing actions, as measured in a conditioned place preference (CPP) paradigm. Arousing and stressful conditions or drug re-exposure can elicit relapse in humans and reinstate drug-seeking in animals. Given the LHA is also implicated in the reinstatement of drug-seeking behaviour, additional studies examined whether AMPH acts within the LHA to reinstate an extinguished CPP produced with systemic AMPH administration. Our results demonstrate that AMPH action within the LHA is sufficient to reinstate drug-seeking behaviour, as measured in this paradigm. Collectively, these observations demonstrate that psychostimulants act within the LHA to elicit affectively neutral arousal and reinstate drug-seeking behaviour.

People attempt to change their lifestyle when obesity impairs their quality of life. The attempts often fail when multiple habits must be changed in unison. Here we explore relations among food addiction, the neurobiology of habits, and caloric restriction, when people seek to return to normal eating behaviour, with particular emphasis on the role of dopaminergic neurotransmission.

Severely obese individuals have specific neurobiological characteristics in common with drug abusers, including low availability of dopamine receptors in the striatum, impaired neuronal responses to dopamine, and reduced activity in prefrontal regions of the cerebral cortex. The neurobiological characteristics suggest that obese people also have a pathological dependence in common with addicts, in the form of food addiction.

Malnutrition and dieting both relate to binge eating, possibly as a compensation for a reduced cognitive reward condition. The combination of caloric restriction and food addiction imparts a high risk of relapse as a result of further reduction of dopaminergic neurotransmission and the subsequent loss of reward. As with drugs of abuse, ingestion of large quantities of sugar in circumstances of uncontrolled eating increases dopamine release in the nucleus accumbens. This and other evidence suggests that abuse of food is a habit learned by means of mechanisms centred in the basal ganglia, with an increased risk of relapse in the presence of associative amplifiers. This risk is predicted by the relationship between dopamine receptor availability in the striatum and sensation-seeking in the form of an inverted U, suggested by recent findings, consistent with two opposite states of hypodopaminergic and hyperdopaminergic neuromodulation.