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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
141

Osprey involvements : historical animal geographies of extinction and return

Garlick, Benjamin Wood January 2017 (has links)
This thesis argues that humans and ospreys in Scotland are materially, bodily and ethically involved with one another. It follows that a separate human or osprey history of species conservation is inadequate. Focused primarily through the entwined experiences of birds and people on Speyside, I examine the unfolding of osprey-human relationships with particular attention to the agency and capacities of nonhuman animals as animals: with geographies and lives of their own. Drawing on the scholarship of Tim Ingold, Giles Deleuze and Donna Haraway, I consider the dwelling, the co-becoming, and the zones of attachment between human and osprey subjects. At the heart of this project has been an investigation of the relationship between the historical and geographical conditions within which osprey life has flourished on its return from extinction in Scotland, and the possibilities for osprey nature that emerge from such conditions. I offer a ‘site ontology’ of osprey involvements, each ‘site’ comprising a material, bodily and ethical event of agency, subjectivity and composition. Often running in parallel to each other, such sites emphasise differentiations of osprey life: their situation within the militarised biopolitics of bird protection and ‘Operation Osprey’; negotiations of avian-human proximity and distances; their nesting geographies amidst the experimental attempts to restore a diminished community to its former range; and the nature of avian existence emerging in the wake of a return from extinction. Drawing on an array of archival material – occasionally supplemented with oral history, avian science and encounters in the field – the thesis proposes a lively historical geography of animal involvement.
142

Condicionamento respondente aversivo: efeitos de diferentes intervalos de apresentação do CS durante a extinção sobre a ressurgência da CR / Aversive respondent conditioning: Effects of different intervals of CS presentation during extinction on the ressurgence of the CR

Zuccolo, Pedro Fonseca 28 May 2014 (has links)
Pesquisas sobre condicionamento respondente envolvendo estímulos aversivos mostram que respostas condicionais (CRs) podem ressurgir depois de extintas. Schiller et al. (2010) demonstraram que as CRs podem ser inibidas de forma duradoura se durante a extinção for dado um intervalo entre a primeira apresentação do CS e as demais apresentações. Esta pesquisa consiste na replicação desse experimento como forma de iniciar uma série de estudos sobre extinção respondente no Laboratório de Análise Biocomportamental (LABC). Foram utilizados 11 participantes adultos, expostos a estimulação elétrica leve (US) e três quadrados coloridos (CSs). As alterações na condutância da pele frente à apresentação do US e dos CSs foram as medidas da UR e CR, respectivamente. Os sujeitos, divididos em dois grupos (experimental e controle), passaram por três estágios consecutivos com intervalos de 24 hr: condicionamento, extinção e teste de ressurgência. Eles diferiram entre si apenas quanto ao tratamento recebido na fase de extinção. No condicionamento, dois estímulos foram pareados com o US (CSa+ e CSb+) e um nunca foi pareado (CS-) com o US. Na extinção, os participantes foram expostos apenas aos três CSs sem US. Apenas no grupo experimental foi dado um intervalo de 10 min entre a primeira e as demais apresentações do CSa+. No teste de ressurgência, foram feitas quatro apresentações do US, seguidas de intervalo de 10 min e sucessivas apresentações dos três CSs sem o US. Na média, os grupos não diferiram entre si, apresentando igualmente condicionamento, extinção e aumento das amplitudes das CRs frente a todos os estímulos no teste. Porém, foi grande a variabilidade entre participantes em ambos os grupos: além de diferirem quanto ao padrão de condicionamento e extinção, nem todos apresentaram ressurgência. Esses dados não replicam o estudo de Schiller et al. (2010), sugerindo que mais análises são necessárias para que sejam identificadas as variáveis que controlam o condicionamento e a extinção respondentes / Research on respondent conditioning involving aversive stimuli have shown that conditional responses (CRs) may reappear after extinction. Schiller et al., (2010) have demonstrated that CR inhibition may be long-lasting if there is a longer interval between the first and the remaining presentations of the CS during extinction. This research aimed at replicating the previously described experiment as a way of starting a series of investigations on respondent extinction in the Biobehavioral Analysis Laboratory (LABC). We recruited 11 adult participants who were exposed to a mild electrical stimulation (US) and were shown three colored squares (CSs). Skin conductance responses during US and CS presentations were used as measures of URs and CRs, respectively. The subjects were divided into two groups (experimental and control) and went through three consecutive stages separated by a 24 hr interval: conditioning, extinction, and ressurgence test. These groups differed from each other only regarding the treatment received during extinction. In conditioning, two stimuli were paired with the CS (CSa+ and CSb+) while a third stimulus was never paired with the US. In the extinction phase, participants were exposed to the three CSs without the US. There was a 10 min interval between the first and the remaining presentations of the CSa+ only for the experimental group. In the test phase, the US was administered four times, which was followed by a 10 min interval and sucessive presentations of all CSs without the US. In average, groups did not differ from each other, presenting equivalent levels of conditioning, extinction, and an increase in CR amplitudes following presentation of all stimuli in the test phase. However, we observed significant between-subject variability within both groups: besides presenting different patterns of conditioning and extinction, not every subject showed CR ressurgence. These data do not replicate the findings reported by Schiller et al. (2010), suggesting that further analysis are needed to identify variables that control conditioning and extinction
143

Paléobiodiversité des ostracodes à la limite Permien moyen - Permien supérieur / Ostracods palaeobiodiversity at the Middle - Late Permian boundary

Zazzali, Sindbad 07 April 2016 (has links)
Les ostracodes, microcrustacés (Arthropoda), sont relativement abondants dans les archives paléontologiques. Sensibles aux variations paléoenvironnementales, la composition des assemblages et leur diversité sont d’excellents marqueurs des changements qui affectent le benthos marin néritique. Leur diversité est connue pour être fortement affectée par la crise biologique marquant la limite Permien-Trias, mais leur histoire à la fin du Permien moyen reste peu documentée.Près de 10 Ma avant la limite Permien-Trias, à la fin du Permien moyen, un important épisode d’extinction intervient, préfigurant le déclin de la biodiversité à la fin du Paléozoïque.L’étude systématique des échantillons prélevés le long des coupes de Chaotian (province du Sichuan, Chine) et de Penglaitan (province du Guangxi, Chine) a permis l’identification de 115 espèces d’ostracodes, dont 7 nouvelles. Le travail réalisé sur ces coupes constitue la toute première étude des événements de la fin du Permien moyen et du début du Permien supérieur s’appuyant sur l’observation des assemblages d’ostracodes. L’état de conservation des carapaces d’ostracode, étudié lors de ce travail, enregistre les effets de la fin d’un épisode de régression et le début d’un épisode de transgression au sommet du Permien moyen à Penglaitan. Les résultats s’avèrent en accord avec les données lithologiques et paléontologiques présentées dans la littérature, un modèle de reconstitution paléoenvironnementale basé sur les données de préservation des ostracodes est proposé.Une analyse critique de la qualité du jeu de données a permis d’évaluer l’influence des biais d’échantillonnage sur la représentativité du matériel fossile dans les études sur la paléobiodiversité et la paléoécologie. Les biais peuvent être corrigés par un traitement méthodologique approprié qui rend valide la comparaison des données de biodiversité. La richesse générique et spécifique décroît sensiblement au cours du Capitanien. Le passage du Permien moyen au Permien supérieur enregistre une augmentation de la richesse spécifique, malgré une faible diversité générique. L’ordre des Palaeocopida apparait ici affecté par une baisse de diversité générique et spécifique au Wuchiapingien inférieur. Si ces résultats ne permettent pas pour l’iPermiannstant de caractériser un événement global de renouvellement des communautés d’ostracodes, l’étude de matériel fossile provenant d’autres régions du monde permettra de définir l’ampleur des phénomènes observés. / Ostracods, microcrustaceans (Arthropoda), are quite abundant in the fossil record. Highly dependent to palaeoenvironmental conditions, their diversity and the assemblages’ composition are good indicators of changes affecting neritic marine benthos. Ostracods are known to be deeply affected by the Permian-Triassic crisis, but their history is poorly documented for the end of Middle Permian.About10 My before the Permian-Triassic boundary, the end of Middle Permian is characterized by a major extinction episode, which could be the first step of end-Palaeozoic biodiversity drop.Systematic study carried out on Chaotian section (Sichuan Province, P.R. China) and the Penglaitan section (Guangxi Province, P.R. China) samples allowed the identification of 115 species, including seven new species. The work carried out on these two sections provides the first study of end-Middle Permian extinction event, based on the observation of ostracod assemblages.Study of carapace preservation at Penglaitan section, highlighted the end of a regression phase and the beginning of a transgression phase at the top of Middle Permian. These results are relevant with lithologic and palaeontological data from literature. Thus, a palaeoenvironmental reconstruction model has been proposed, based on ostracod preservation data.An estimation of sampling bias consequences on fossil dataset representativeness in palaeobiodiversity and palaeoecology studies was realised. These biases could be corrected by an appropriate methodology allowing comparisons of biodiversity datum. Biodiversity data reveals a decrease of generic and specific richness during Capitanian. Specific richness increased passing the Middle-Upper Permian boundary. Palaeocopida order seems here affected by a generic and specific richness decline at basal Wuchiapingian. If these results do not allow for the time being to characterize a global ostracod turnover, further studies on material from other regions in the world will allow defining the extent of the observed phenomena.
144

Processus d'émergence des patrons de diversité supra-spécifiques lors des radiations évolutives / Processes of emergence of large scale diversity patterns during evolutionary radiations

Gascuel, Fanny 28 June 2016 (has links)
Les radiations évolutives sont des phénomènes de diversification rapide, et une source majeure de la diversité biologique sur Terre. J'explore ici l'hypothèse selon laquelle les mécanismes écologiques et génétiques à la base des radiations évolutives structurent les patrons macroécologiques et macroévolutifs de diversité. Pour ce faire, j'analyse les prédictions de plusieurs modèles de radiation émergeant des dynamiques spatio-temporelles à l'échelle individuelle. Ces analyses montrent d'abord que la structuration spatiale est un facteur majeur de diversité et d'endémisme au sein des archipels océaniques, en raison d'interactions entre dispersion et spéciation allopatrique. L'intégration de la dynamique des paysages et des processus d'interactions compétitives révèle ensuite comment ces facteurs se combinent pour structurer la forme des arbres phylogénétiques, et notamment générer des arbres déséquilibrés et une décélération du tempo de branchement, souvent observés dans les phylogénies moléculaires. J'explore alors les mécanismes responsables de cette décélération. Je montre qu'elle reflète une diversité-dépendance négative du taux de spéciation, liée à une réduction de la persistance et différentiation écologique des nouvelles populations. Le taux d'extinction n'est lui pas influencé par la diversité, les extinctions étant ici surtout causées par une combinaison d'exclusion compétitive et d'hybridation d'espèces incipientes. Enfin, je mets en évidence l'importance, lors d'une crise d'extinction, de la topologie rangée des arbres phylogénétiques et de la distribution des extinctions sur les pertes de diversité phylogénétique, et donc sur le potentiel d'évolution future. / Evolutionary radiations are phenomena of rapid diversification, and one of the major sources of biodiversity on Earth. Here, I explore the hypothesis that ecological and genetic mechanisms underpinning evolutionary radiations structure macroecological and macroevolutionary patterns of diversity. To this end, I analyse the predictions of several models in which radiations emerge from spatio-temporal dynamics at the scale of the individual. These analyses first show that spatial structure is a major driver of diversity and endemism on oceanic archipelagos due to interactions between dispersal and allopatric speciation. Second, by integrating landscape dynamics and the processes of competitive interactions, I reveal how these factors combine to shape phylogenetic trees, and in particular to beget trees that are unbalanced and exhibit a deceleration in branching tempo, which is often observed on molecular phylogenies. I then explore the mechanisms responsible for this deceleration. I show that it reflects a negative diversity-dependence of the speciation rate, itself linked to a reduction in the persistence and ecological differentiation of new populations. The extinction rate is, on the other hand, uninfluenced by species diversity, extinctions being here mainly caused by a combinaison of competitive exclusion and hybridization of incipient species. Finally, I show that during mass extinctions the ranked topology of phylogenetic trees and the distribution of extinctions among the tips have a strong impact on the loss of phylogenetic diversity, and hence on the potential for future evolution.
145

Condicionamento respondente aversivo: efeitos de diferentes intervalos de apresentação do CS durante a extinção sobre a ressurgência da CR / Aversive respondent conditioning: Effects of different intervals of CS presentation during extinction on the ressurgence of the CR

Pedro Fonseca Zuccolo 28 May 2014 (has links)
Pesquisas sobre condicionamento respondente envolvendo estímulos aversivos mostram que respostas condicionais (CRs) podem ressurgir depois de extintas. Schiller et al. (2010) demonstraram que as CRs podem ser inibidas de forma duradoura se durante a extinção for dado um intervalo entre a primeira apresentação do CS e as demais apresentações. Esta pesquisa consiste na replicação desse experimento como forma de iniciar uma série de estudos sobre extinção respondente no Laboratório de Análise Biocomportamental (LABC). Foram utilizados 11 participantes adultos, expostos a estimulação elétrica leve (US) e três quadrados coloridos (CSs). As alterações na condutância da pele frente à apresentação do US e dos CSs foram as medidas da UR e CR, respectivamente. Os sujeitos, divididos em dois grupos (experimental e controle), passaram por três estágios consecutivos com intervalos de 24 hr: condicionamento, extinção e teste de ressurgência. Eles diferiram entre si apenas quanto ao tratamento recebido na fase de extinção. No condicionamento, dois estímulos foram pareados com o US (CSa+ e CSb+) e um nunca foi pareado (CS-) com o US. Na extinção, os participantes foram expostos apenas aos três CSs sem US. Apenas no grupo experimental foi dado um intervalo de 10 min entre a primeira e as demais apresentações do CSa+. No teste de ressurgência, foram feitas quatro apresentações do US, seguidas de intervalo de 10 min e sucessivas apresentações dos três CSs sem o US. Na média, os grupos não diferiram entre si, apresentando igualmente condicionamento, extinção e aumento das amplitudes das CRs frente a todos os estímulos no teste. Porém, foi grande a variabilidade entre participantes em ambos os grupos: além de diferirem quanto ao padrão de condicionamento e extinção, nem todos apresentaram ressurgência. Esses dados não replicam o estudo de Schiller et al. (2010), sugerindo que mais análises são necessárias para que sejam identificadas as variáveis que controlam o condicionamento e a extinção respondentes / Research on respondent conditioning involving aversive stimuli have shown that conditional responses (CRs) may reappear after extinction. Schiller et al., (2010) have demonstrated that CR inhibition may be long-lasting if there is a longer interval between the first and the remaining presentations of the CS during extinction. This research aimed at replicating the previously described experiment as a way of starting a series of investigations on respondent extinction in the Biobehavioral Analysis Laboratory (LABC). We recruited 11 adult participants who were exposed to a mild electrical stimulation (US) and were shown three colored squares (CSs). Skin conductance responses during US and CS presentations were used as measures of URs and CRs, respectively. The subjects were divided into two groups (experimental and control) and went through three consecutive stages separated by a 24 hr interval: conditioning, extinction, and ressurgence test. These groups differed from each other only regarding the treatment received during extinction. In conditioning, two stimuli were paired with the CS (CSa+ and CSb+) while a third stimulus was never paired with the US. In the extinction phase, participants were exposed to the three CSs without the US. There was a 10 min interval between the first and the remaining presentations of the CSa+ only for the experimental group. In the test phase, the US was administered four times, which was followed by a 10 min interval and sucessive presentations of all CSs without the US. In average, groups did not differ from each other, presenting equivalent levels of conditioning, extinction, and an increase in CR amplitudes following presentation of all stimuli in the test phase. However, we observed significant between-subject variability within both groups: besides presenting different patterns of conditioning and extinction, not every subject showed CR ressurgence. These data do not replicate the findings reported by Schiller et al. (2010), suggesting that further analysis are needed to identify variables that control conditioning and extinction
146

Prey-size selectivity in the bivalve <em>Chione</em> in the Florida Pliocene-Pleistocene: A reevaluation

Paul, Shubhabrata 06 November 2008 (has links)
Previous study of drilling predation on the bivalve Chione during the late Neogene of Florida suggested that prey-size selectivity of predators was disrupted by species turnover and morphological change within the prey genus. More recent experimental work, however, showed that at least some of these changes can be attributed to the confounding effects of facies shifts between naticid-dominated, muricid-dominated, and mixed predator assemblages. As muricids have the most abundant and continuous fossil record and are most responsible for predation on the Chione bivalve in modern benthic ecosystems of Florida, we use new criteria to isolate the muricid component of the Chione drillhole record and analyze the history of this type of predator independently. Our analysis, based on drilled Chione from four Plio-Pleistocene formations in Florida, does not support the previous scenario of disruption at the end of the Pliocene followed by predator recovery. Rather, selected prey size has steadily increased since the middle Pliocene, although the stereotypy of prey-size selection behaviors has decreased. In order to explain this trend, I performed a series of statistical analyses to explore factors most likely to have influenced muricid prey-size stereotypy. The timing of Species turnover within the prey lineage or change in prey phenotype does not correlate with the timing of changes in prey-size stereotypy and, therefore, cannot explain the observed changes in muricid behavior. Presence of secondary predators may also influence predator-prey interactions, because predators forage sub-optimally to ensure greater safety in the presence of enemies. Results indicate that secondary predation pressure decreased at the Caloosahatchee-Bermont boundary without any evident change in muricid prey-size stereotypy and hence refute the hypothesis that secondary predation induced sub-optimal foraging. A third factor tested is prey density, which plays a major role in predator-prey interactions in other systems by thwarting a predator's ability to single out the preferred individual prey. Increased Chione prey density correlates with and provides support for increased confusion among the muricid predators and hence driving the increased sub-optimal behavior reflected by the increased variability in prey-size selection. This is the first time prey density effect has been considered and its importance here over all other factors suggests that it may be a critical factor in short- and long-term predator behavior trends in fossil record.
147

The role of the prefrontal cortex in cocaine and heroin seeking following extinction training

Cosme, Caitlin Victoria 15 December 2017 (has links)
The prefrontal cortex (PFC) is considered a critical node in the neural circuitry underlying drug-seeking behaviors. However, the mechanisms by which this region influences drug seeking and whether or not the lateral PFC mediates cocaine or heroin seeking are questions that have yet to be answered. To expand on the role of the PFC in drug seeking, rats were trained on either heroin or cocaine self-administration for a minimum of 12 days before undergoing extinction training and subsequent reinstatement tests (cued and drug-prime). All pharmacological manipulations were delivered immediately prior to reinstatement testing and were targeted at either the ventral region of the medial PFC, the infralimbic cortex (IL), the anterior portion of the medial PFC, the medial orbitofrontal cortex (mOFC), the anterior region of the insular cortex, the dorsal agranular insular cortex (AId), or the posterior region of the insular cortex, the posterior insular cortex (PIc). In chapter 1, D1 and D2 antagonists were administered into the IL and mOFC prior to cued and cocaine-prime reinstatement. Although previous studies found that the IL inhibits cocaine seeking, blocking D1 receptor activity in this region reduced cued reinstatement and had no effect on cocaine-prime reinstatement, indicating that the IL can promote cocaine seeking under certain circumstances. In contrast, blocking D1 receptors in the mOFC reduced all forms of reinstatement that were examined. Blocking D2 receptors in either region had no effect on cocaine seeking. Our data are the first to demonstrate a role for the mOFC in cocaine seeking and suggest that although the IL and mOFC lie immediately adjacent to one another, they play distinct roles in mediating cocaine seeking. In chapter 2, we pharmacologically inactivated the AId and PIc via a GABA agonist administered immediately prior to both cocaine and food seeking. Reversible inactivation of the AId reduced cued reinstatement but had no effect on cocaine-prime reinstatement. In contrast, inactivating the PIc had no effect on any form of cocaine seeking. Additionally, blocking the AId during cued and food-prime reinstatement had no effect on food seeking, indicating the role of the AId in reinstatement is specific to cocaine seeking and not general motivated behavior. Additionally, blocking CRF1 receptors in the AId blocked cued reinstatement, suggesting a possible mechanism whereby the AId is influencing cocaine seeking. These data are the first to establish a role for the AId in cocaine seeking and demonstrate that although the PIc influences alcohol and nicotine seeking, it does not mediate cocaine seeking. Chapter 3 further examined the role of the AId in cocaine seeking and expanded the influence of the insular cortex in drug seeking to heroin. AId D1 receptor blockade reduced both cued and cocaine-prime reinstatement following extinction training, whereas D2 receptor blockade had no effect on cocaine seeking. These results establish a role for the AId in cocaine-prime reinstatement, as pharmacological inactivation showed no role for the AId in cocaine-induced drug seeking. Additionally, blocking the AId during heroin seeking potentiated cued reinstatement whereas blocking the PIc during heroin seeking reduced cued reinstatement. These results demonstrate a role for the insular cortex in heroin seeking that has never been shown before and further explain how the AId may be influencing cocaine seeking.
148

The Effects of Conditioned Reinforcers on Extinction When Delivered on Schedules of Extinction

Barnard, Linda L. 01 May 1990 (has links)
The purpose of the present research was to examine extinction of responding with regard to the rapidity and thoroughness of the process when conditioned reinforcement was available on one of five schedules during extinction. Forty-five mixed-breed pigeons served as subjects with 15 in each of three experiments. Reinforcement training schedules were as follows: Experiment 1, continuous; Experiment 2, fixed ratio 15; Experiment 3, variable-interval one-minute. After training, subjects experienced one of five extinction procedures (here called schedules of extinction) which were as follows: traditional schedule without keylight did not provide conditioned reinforcement; traditional with keylight had the keylight on continuously but withheld other conditioned reinforcement (no schedule, per se, was used); the remaining three schedules (i.e., continuous, fixed ratio 15, and variable-interval one-minute) provided the following four conditioned reinforcers: the sound of the food magazine, the hopper light, the sight of food, and the keylight. Predictions for responding were based on the discrimination hypothesis which states that the more alike training and extinction conditions are, the slower the process of extinction. In order to compare response rates among subjects, a percentage of baseline responding was computed. Four spontaneous recovery tests were conducted to measure the thoroughness of the extinction procedures. Results did not support predictions based on the discrimination hypothesis; that is, subject response rates did not appear to be affected by the similarity of the extinction condition to previous training history. The second finding was that the most rapid and thorough extinction was obtained when the extinction schedule was traditional without keylight. When conditioned reinforcement was available, the continuous extinction schedule produced the most rapid and thorough extinction. The third major finding was that the schedule of unconditioned reinforcement was more predictive of extinction responding than was the conditioned reinforcement schedule during extinction. The last finding was that a subject's pattern of responding was typical of the schedule whether it was on an unconditioned or a conditioned reinforcement schedule. It is suggested that extinction-of-a-human-intervention strategies might be more effective if conditioned reinforcement was identified and controlled.
149

Resistance to Change of Ethanol Self-Administration: Effects of Naltrexone and Extinction

Jimenez-Gomez, Corina 01 May 2005 (has links)
Drug self-administration has proven to be an adequate model for assessing variables that contribute to the maintenance of drug taking. The present experiment was concerned with the persistence of drug self-administration, a defining characteristic of drug dependence and abuse. Findings from studies of the resistance to change of food-maintained responding may contribute to a better understanding of the persistence of drug abuse and dependence. Using an animal model of alcohol self-administration, this study evaluated the effects of rate of reinforcement on the persistence of ethanol self-administration in rats in the face of behavioral (i.e., extinction) and pharmacological (i.e., naltrexone) disruptors. Four experimentally naive Long Evans rats were trained to respond for a 10% (vol/vol) ethanol solution on a multiple variable-interval (VI) 15-s VI 45-s schedule of reinforcement. Baseline response rates were higher in the component that provided higher rates of ethanol delivery. Consistent with behavioral momentum theory, responding was more resistant to extinction in the component with higher rates of ethanol delivery. Conversely, disruption with naltrexone (1.0, 3.0, 10.0 mg/kg, s.c.), injected one hour before the session, resulted in no differential resistance to change of responding. The results are interpreted in terms of the effect of naltrexone on the incentive-motivational properties of the stimulus context.
150

A Comparison of Resistance to Extinction Following Dynamic and Static Schedules of Reinforcement

Craig, Andrew R. 01 May 2013 (has links)
Resistance to extinction of single-schedule performance is negatively related to the reinforcer rate that an organism experienced in the pre-extinction context. This finding opposes the predications of behavioral momentum theory, which states that resistance to change, in general, is positively related to reinforcer rates. The quantitative model of extinction provided by behavioral momentum theory can describe resistance to extinction following single schedules in a post-hoc fashion, and only if the parameters of the model are allowed to vary considerably from those typically derived from multiple- schedule preparations. An application of the principles of Bayesian inference offers an alternative account of extinction performance following single schedules. According to the Bayesian change-detection algorithm, the temporal intervals of non-reinforcement that an organism experiences during extinction are compared to the temporal distribution of reinforcers that the organism experienced during baseline. A transition to extinction is more readily detectable when the previously collected distribution of reinforcers in timeis populated with relatively short intervals (i.e., when more frequent reinforcement was experienced during baseline). The Bayesian change-detection algorithm also suggests that changes in reinforcer rates are more detectable when organisms have temporally proximal experience with frequently changing rates. The current experiment investigated this novel prediction. Pigeons pecked keys for food under schedules of reinforcement that arranged either relatively dynamic reinforcer rates or relatively static rates across conditions. Following each period of reinforcement, resistance to extinction was assessed. Persistence was greater following static contingencies than following dynamic contingencies for the majority of subjects. These data provide support for the Bayesian approach to understanding operant extinction and might serve to extend behavioral momentum theory by offering change detection as an additional mechanism through which extinction occurs.

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