Endogenous retrovirsuses (ERVs) have long been known to influence gene expression in plants in important ways, but what of their roles in mammals? Our relatively sparse knowledge in that area was recently increased with the finding that ERVs can influence the expression of mammalian resident genes by disrupting transcriptional termination. For many mammalian biologists, retrotransposition is considered unimportant except when it disrupts the reading frame of a gene, but this view continues to be challenged. It has been known for (...) some time that integration into an intron can create novel transcripts and integration upstream of a gene can alter the expression of the transcript, in many cases producing phenotypic consequences and disease. The new findings on transcriptional termination extend the opportunities for retrotransposons to play a role in human disease. (shrink)

That endogenous retrovirus (ERV) is present within the placenta of humans and other mammals has been known for the past 25 years, but the significance of this observation is still not fully understood. Much molecular biological data have emerged in recent years to support the earlier electron microscopic data on the presence of placental ERV. The evidence for ERV in animal and human placental tissue is presented, then integrated with data on the the presence of ERV in a (...) range of other tissues, in particular teratocarcinoma cells. Placental invasiveness and maternal immunosuppression are then discussed in relation to metalloproteinase secretion, the immunosuppressive potential of retroviruses, and placental growth factors, while the evidence for a functional link between placental proto‐oncogenes and trophoblast malignancy is reviewed. Finally, placental development, structure, and life span are discussed within an evolutionary context. The hypothesis that one or more ancient trophoblastic ERVs could have played a role in the evolution and divergence of all placental mammals is evaluated. BioEssays 20:307‐316, 1998. © 1998 John Wiley & Sons, Inc. (shrink)

Several studies have revealed the presence in human DNA of thousands of endogenous retrovirus genomes, or HERVs. Many HERVs are related to extant retroviruses that infect other vertebrates and some have been present in the germ line of primates for millions of years. Although the HERVs that have been isolated are defective and thus do not encode infectious retroviruses, there may be HERVs that are capable of infection. In addition, because HERVs are so ancient in the human lineage, (...) evolution of the human genome may have included the acquisition of some HERV genes for strictly cellular functions. (shrink)

A number of observations have led researchers to postulate that, despite being replication‐defective, human endogenous retroviruses (HERVs) may have retained the potential to cause or contribute to disease. However, mechanisms of HERV pathogenicity might differ substantially from those of modern infectious retroviruses or of the infectious precursors of HERVs. Therefore, novel pathways of HERV involvement in disease pathogenesis should be investigated. Recent technological advances in sequencing and bioinformatics are making this task increasingly feasible. The accumulating knowledge of HERV biology (...) may also facilitate the definition and general acceptance of criteria that establish HERV pathogenicity. Here, we explore possible mechanisms whereby HERVs may cause disease and examine the evidence that either has been or should be obtained in order to decisively address the pathogenic potential of HERVs. (shrink)

Remnants of ancient retroviral infections during evolution litter all mammalian genomes. In modern humans, such endogenous retroviral (ERV) sequences comprise at least 8% of the genome. While ERVs and other types of transposable elements undoubtedly contribute to the genomic “junk yard”, functions for some ERV sequences have been demonstrated, with growing evidence that ERVs can be important players in gene regulatory processes. Here we focus on one particular large family of human ERVs, termed HERVH, which several recent studies suggest (...) has a key regulatory role in human pluripotent stem cells. Remarkably, this is not the first instance of an ERV controlling pluripotency. We speculate as to why this convergent evolution might have come about, suggesting that it may reflect selection on the virus to extend the time available for transposition. Alternatively it may reflect serendipity alone. (shrink)

The mammalian placenta exhibits elevated expression of endogenous retroviruses (ERVs), but the evolutionary significance of this feature remains unclear. I propose that ERV‐mediated regulatory evolution was, and continues to be, an important mechanism underlying the evolution of placental development. Many recent studies have focused on the co‐option of ERV‐derived genes for specific functional adaptations in the placenta. However, the co‐option of ERV‐derived regulatory elements could potentially lead to the incorporation of entire gene regulatory networks, which, I argue, would facilitate (...) relatively rapid developmental evolution of the placenta. I suggest a model in which an ancient retroviral infection led to the establishment of the ancestral placental developmental gene network through the co‐option of ERV‐derived regulatory elements. Consequently, placental development would require elevated tolerance to ERV activity. This in turn would expose a continuous stream of novel ERV mutations that may have catalyzed the developmental diversification of the mammalian placenta. (shrink)

Ravelingien et al1 argue that we should recategorise people in a permanent vegetative state as dead. Although the dilemma they describe is very real, their solution will not work. Other respondents to this paper have advanced several powerful arguments against the attempt to describe patients in a PVS as dead. Fortunately, the original argument contains sufficient resources for developing an alternative solution to this dilemma without having to radically change the current legal or social status of patients in a PVS. (...) In fact, patients in a PVS may be enrolled in xenotransplantation experiments, provided that their prior informed consent has been sought.The motivation for the original paper was to resolve an apparently intractable ethical conflict. On the one hand, there are powerful ethical and medical reasons for proceeding with research into the transplantation of non-human organs into human patients, whereas on the other, there are equally powerful ethical reasons for blocking whole-organ transplant experiments. These reasons are unusual in that special problems with xenotransplantation will block experiments that are permitted in other cases. In particular, the unquantifiable risk of a pandemic triggered by diseases such as porcine endogenous retrovirus crossing the species barrier will either block the research or expose subjects to the risk of indefinite quarantine . The authors also argue that the restrictions placed on transplant recipients and the possibility of long-term and intrusive monitoring, restrictions on sexual contacts and reproduction, and possible confinement represent excessive and ethically unjustifiable burdens. Over time, the recipients may wish to withdraw their consent, but the risks to public health would prevent them from doing so, thereby violating the basic principle that subjects of scientific and medical experiments should be able to revise or withdraw consent . …. (shrink)

The placenta arose during mammalian evolution, which is recent in evolutionary terms. Genetic changes underlying placental development remain identifiable by the new science of comparative genomics (approximately post‐2000). Randomly arising features of genomes including endogenous retroviruses and transposable elements have provided structural genes and gene‐regulatory motifs responsible for innovations in placental biology. Stochastic genetic events indeed contribute to new functionality. Theologically, random mutations are part of the strategy by which the divine purpose for humanity is attained. Placental function critically (...) underlies human brain development, and suboptimal function, associated with environmental conditions and maternal distress, contributes to mental health deficits in the offspring. Many enter life with handicaps arising from contingent events in utero, mandating understanding, compassion, and socioemotional support, imperatives native to moral including biblical values. The extended period of development afforded by placentation enables prenatal parenting, with implications for sensitive and devoted parental commitment. (shrink)

In Greg Bear’s critically acclaimed science fiction novel Darwin’s Radio, the activation of an endogenous retrovirus (SHEVA), ironically located in a “noncoding region” of the human genome, causes extreme symptoms in women worldwide, including miscarriages. In the United States, a task force is assembled to control the pandemic crisis and to find out how SHEVA operates at the genomic level. However, as the story unfolds, it becomes manifest that SHEVA is too complex to decode in this way and, (...) moreover, that it is not a disease at all. Biologist Kay Lang speculates that SHEVA is triggered by signals from the environment, and that newborn SHEVA children will be a new variation or species of Man. In this essay I analyze Bear’s literary experiment with science along Deleuze and Guattari’s important, but largely overlooked, concepts of State science and nomad science. Bear’s novel gives narrative form to nomad-scientific ideas about life, notably Lynn Margulis’s theory of endosymbiogenesis, which holds that a species’ DNA is an assemblage of many genomes acquired in symbiotic relations. The import of Bear’s informed speculations, I argue, is not crass prediction but a nomadic vision of life as always already different (impure, infected) and in becoming—a counterpoint to the image of the double helix as the bedrock of human identity. Darwin’s Radio is a key example of how fiction can be an excellent partner for science, technology, and society, analyzing and intervening in debates about life and laying bare epistemological and biopolitical tensions of technoscience. (shrink)

Transposable elements (TEs) are sequences currently or historically mobile, and are present across all eukaryotic genomes. A growing interest in understanding the regulation and function of TEs has revealed seemingly dichotomous roles for these elements in evolution, development, and disease. On the one hand, many gene regulatory networks owe their organization to the spread of cis‐elements and DNA binding sites through TE mobilization during evolution. On the other hand, the uncontrolled activity of transposons can generate mutations and contribute to disease, (...) including cancer, while their increased expression may also trigger immune pathways that result in inflammation or senescence. Interestingly, TEs have recently been found to have novel essential functions during mammalian development. Here, the function and regulation of TEs are discussed, with a focus on LINE1 in mammals. It is proposed that LINE1 is a beneficial endogenous dual regulator of gene expression and genomic diversity during mammalian development, and that both of these functions may be detrimental if deregulated in disease contexts. (shrink)

Current research on the origin of DNA and RNA, viruses, and mobile genetic elements prompts a re-evaluation of the origin and nature of genetic material as the driving force behind evolutionary novelty. While scholars used to think that novel features resulted from random genetic mutations of an individual’s specific genome, today we recognize the important role that acquired viruses and mobile genetic elements have played in introducing evolutionary novelty within the genomes of species. Viral infections and subviral RNAs can enter (...) the host genome and persist as genetic regulatory networks. Persistent viral infections are also important to understand the split between great apes and humans. Nearly all mammals and nonhuman primates rely on olfaction, i.e., chemoreception as the basis of the sense of smell for social recognition, group membership, and the coordination of organized social life. Humans, however, evolved other means to establish social bonding, because several infection waves by endogenous retroviruses caused a loss of odor receptors in human ancestors. The human independence from olfaction for social recognition was in turn one driver of the rather abrupt human transition to dependence on visual information, gesture production, and facial recognition that are at the roots of language-based communication. (shrink)

The theory of biological evolution has often provoked disagreement, which has frequently been divisive and counterproductive. At other times this scientific paradigm has been discussed with an apologetic intent, to explain why the science of biology and the theology of creation cannot be seen to be mutually exclusive. This paper urges Christians to move decisively to a third type of discourse. The new field of comparative genetics has provided conclusive evidence that biological evolution has given rise to the diversity of (...) living forms, including human beings. Consequently, Christians should, with confidence, gladly accept the evolutionary paradigm and look upon evolution as a divinely ordained historical process that develops through random (stochastic, free) process, but that leads to a divinely purposed consummation. As a result, biological history in its freedom but directedness to God’s final purposes should elicit wonder. People who have come to faith in the God revealed redemptively in Jesus should uninhibitedly offer adoration and praise for evolutionary fruitfulness. Worship should characterise the human response to biological history.[1] [1] In appreciation of Professor Tom McLeish FRS, scientist, teacher, theologian. (shrink)

The pituitary hormone prolactin (PRL) is best known for its role in the regulation of lactation. Recent evidence furthermore indicates PRL is required for normal reproduction in rodents. Here, we report on the insertion of two transposon-like DNA sequences in the human prolactin gene, which together function as an alternative promoter directing extrapituitary PRL expression. Indeed, the transposable elements contain transcription factor binding sites that have been shown to mediate PRL transcription in human uterine decidualised endometrial cells and lymphocytes. We (...) hypothesize that the transposon insertion event has resulted in divergent (pituitary versus extrapituitary) expression of prolactin in primates, and in differential actions of pituitary versus extrapituitary prolactin in lactation versus pregnancy respectively. Importantly, the TE insertion might provide a context for some of the conflicting results obtained in studies of PRL function in mice and man. (shrink)

Why do people who disagree about one subject tend to disagree about other subjects as well? In this paper, we introduce a model to explore this phenomenon of ‘epistemic factionization’. Agents attempt to discover the truth about multiple propositions by testing the world and sharing evidence gathered. But agents tend to mistrust evidence shared by those who do not hold similar beliefs. This mistrust leads to the endogenous emergence of factions of agents with multiple, highly correlated, polarized beliefs.

Retroviral vectors utilize the biochemical processes unique to retroviruses, to transfer genes with high efficiency into a wide variety of cell types in tissue culture and in living animals. With such vectors, the effect of newly introduced genes and the mechanism of gene expression can be studied in cell types so far refractory to other methods of transfer.

This paper develops a mechanistic account of basic mental agency by identifying similarities between two of its major exemplars: endogenous attention and imagination. Five key similarities are identified: i) that both capacities are driven by currently prioritised goals that are either person-level or apt to become person-level. ii) that both deliver their outputs to the working memory iii) that both range across all and only conceptual contents; iv) that both proceed under the guidance of norms and/or habits; and v) (...) that both directly activate rather than inhibit content. These five features are consolidated by proposing that basic mental agency is essentially the power to call for conceptual content and hold it within our working memories. (shrink)

Evolutionary biology is striking for its ability to explain a large and diverse range of empirical phenomena on the basis of a few general theoretical principles. This article offers a philosophical perspective on the way that evolutionary biology has come to achieve such impressive generality, by focusing on “the strategy of endogenization”. This strategy involves devising evolutionary explanations for biological features that were originally part of the background conditions, or scaffolding, against which such explanations take place. Where successful, the strategy (...) moves biology a step closer to the ideal of explaining as much as possible from evolutionary first principles. The strategy of endogenization is illustrated through a series of biological examples, historical and recent, and its philosophical implications are explored. (shrink)

La plupart des projets d’architectures cognitives dans les sciences cognitives et des explications des processus cérébraux dans les neurosciences interprètent l’esprit/cerveau comme réactif : le processus est déclenché par un stimulus et se termine par une réponse. Mais il y a de plus en plus de données laissant penser que le cerveau est endogéniquement actif : des oscillations de l’activité électrochimique à de multiples fréquences ont lieu dans le cerveau même en l’absence de stimuli et ceux-ci servent plutôt à moduler (...) ces oscillations qu’à déclencher l’activité. De plus, des données montrent que cette activité endogène est utilisée dans diverses activités de traitement de l’information. Je m’appuie sur les données issues des enregistrements cellulaires unitaires, de l’EEG et de l’IRMf en situation passive, afin de soutenir la thèse d’un comportement oscillatoire continu dans le cerveau et d’identifier plusieurs manières dont ce comportement peut contribuer à la cognition. Si les sciences cognitives ont pour but de comprendre comment nous effectuons des tâches cognitives, elles ont besoin de développer des architectures cognitives qui intègrent le type d’activité endogène dynamique présentée par le cerveau. (shrink)

La plupart des projets d’architectures cognitives dans les sciences cognitives et des explications des processus cérébraux dans les neurosciences interprètent l’esprit/cerveau comme réactif : le processus est déclenché par un stimulus et se termine par une réponse. Mais il y a de plus en plus de données laissant penser que le cerveau est endogéniquement actif : des oscillations de l’activité électrochimique à de multiples fréquences ont lieu dans le cerveau même en l’absence de stimuli et ceux-ci servent plutôt à moduler (...) ces oscillations qu’à déclencher l’activité. De plus, des données montrent que cette activité endogène est utilisée dans diverses activités de traitement de l’information. Je m’appuie sur les données issues des enregistrements cellulaires unitaires, de l’EEG et de l’IRMf en situation passive, afin de soutenir la thèse d’un comportement oscillatoire continu dans le cerveau et d’identifier plusieurs manières dont ce comportement peut contribuer à la cognition. Si les sciences cognitives ont pour but de comprendre comment nous effectuons des tâches cognitives, elles ont besoin de développer des architectures cognitives qui intègrent le type d’activité endogène dynamique présentée par le cerveau. (shrink)

Lowest-unique sealed-bid auctions are auctions with endogenous participation, costly bids, and the lowest bid among all unique bids wins. Properties of symmetric NEs are studied. The symmetric NE with the lowest expected gains is the maximin outcome under symmetric strategies, and it is the solution to a mathematical program. Comparative statics for the number of bidders, the value of the item and the bidding cost are derived. The two bidders’ auction is equivalent to the Hawk–Dove game. Simulations of replicator (...) dynamics provide numerical evidence that the symmetric NE with the lowest expected gains is also asymptotically stable. (shrink)

The beginning of the twenty first century has been characterized by the expansion of economics, politics and institutional relations. Using international case studies, this book illustrates the local answer to the challenge of increasing competition. The book introduces the idea of endogenous development, identifying the theoretical roots and defining its main features. It then goes on to indicate how this concept can be used to understand economic dynamics, and to show how the concept is relevant in economic analysis and (...) policy implementation in times of globalization. This work will be of essential interest to academics and policy-makers in planning and development economics. (shrink)

The phenomenon of consciousness has received through the centuries a profusion of interpretations, engaging researchers across many disciplines. Nevertheless, consensus still floats at large. The aim of the present work is therefore twofold. Through the review of a selected number of existing proposals, it will first be considered the extents of their reciprocal compatibility, tentatively shaping an integrated, theoretical profile of consciousness. A new theory, the Endogenous Feedback Network will consequently be introduced which, besides being able to accommodate the (...) main tenets of the reviewed theories, appears able to compensate for the explanatory gaps they leave behind. The EFN proposes consciousness as the phenomenon emerging from a distinct neural network broadcasting the changes associated to mental activations across the brain. It additionally argues for the need to include a 5th element to Ned Block’s taxonomy that is, non-cognitive consciousness. (shrink)

This paper examines the theoretical background and actual behavior in a gaming tournament with endogenous timing where a person has more incentive, structure, and time to form a strategy. The baseline treatment suggests that subgame perfection is a reasonable predictor of behavior –- subjects made 170 of 208 theoretically predicted choices of best actions, with the majority of mistakes made in timing choices by the players who did not survive the cut to the second round. Four sensitivity treatments established (...) that the design feature that lead to more predictable behavior was time to think –- 745 of 960 correctly predicted decisions with more time versus 595 of 960 with less time. A random effects Probit model suggests that the key design feature that closed the gap between predicted and observed behavior was not necessarily the non-linear payoffs created by the tournament design, but rather that the key was providing people with more time to think about their strategy. (shrink)

Retroviruses are unusual amongst animal viruses in their capacity to integrate into host genomes and be transmitted vertically to host progeny. Vertebrate genomes contain numerous and diverse retrovirus‐derived sequences reflecting a long co‐evolutionary history during which genome invasion has occurred repeatedly, with wide‐ranging evolutionary consequences. Over the past 10 years, a detailed picture of retroviral diversity throughout vertebrate genomes has emerged, revealing striking and informative patterns that differ markedly across species. The power of these data to deliver far‐reaching insights (...) into the biology and evolution of retroviruses has been significantly advanced by recent studies identifying ongoing genome invasion in wild populations,(1) and by the characterisation of conserved mechanisms of innate antiretroviral defence.(2,3) BioEssays 28: 1153–1156, 2006. © 2006 Wiley Periodicals, Inc. (shrink)

The goal of this study is to characterize observers’ abilities to discriminate between endogenous and exogenous changes. To do so, we developed a new experimental paradigm. On each trial, participants were shown a dot pattern on the screen. Next, the pattern disappeared and participants were to reproduce it. Changes were surreptuously introduced in the stimulus, either by presenting participants anew with the dot pattern they had themselves produced on the previous trial or by presenting participants with a slightly different (...) dot pattern . We analyzed awareness of the changes and behavioral adaptation to them in a dynamical manner. We observe signal attenuation in the presence of endogenous change, dissociation between self-attribution reports and behavioral effect of agency. We discuss the source of this sensitive attenuation as well as the relation between a minimal or core self and an extended, narrative or autobiographical self. (shrink)

Malignant cells are characterized by an increased content of endogenous formaldehyde formed as a by‐product of biosynthetic processes. Accumulation of formaldehyde in cancer cells is combined with activation of the processes of cellular formaldehyde clearance. These mechanisms include increased ALDH and suppressed ADH5/FDH activity, which oncologists consider poor and favorable prognostic markers, respectively. Here, the sources and regulation of formaldehyde metabolism in cancer cells are reviewed. The authors also analyze the participation of oncoproteins such as fibulins, FGFR1, HER2/neu, FBI‐1, (...) and MUC1‐C in the control of genes related to formaldehyde metabolism, suggesting the existence of two mutually exclusive processes in cancer cells: 1) production and 2) oxidation and elimination of formaldehyde from the cell. The authors hypothesize that the study of the anticancer properties of disulfiram and alpha lipoic acid – which affect the balance of formaldehyde in the body – may serve as the basis of future anticancer therapy. (shrink)

In Africa, the human person is the supreme force, the most powerful and dominant among all created beings. While this decreed power makes the lower beings subservient to humanity, it is only intended to be a source of harmony in the advancement of the hospitality and the joy of the human species. Today, however, the traditional lifestyles of Africans are threatened with virtual extinction by insensitive development over which the indigenous peoples have no participation. Africa has not only acquiesced a (...) scientific technology that has developed its own laws far removed from the known system of nature, it has no self-limiting principle in terms of size, speed and violence to nature and humanity. Consequent upon this incongruity, the machine has replaced the human person thus degrading the ecology and resources necessary for harmonious living. This chapter argues that, African endogenous knowledge is strategic heritage resource to salvage the technologically abused environment for sustainable agro-ecological living. The chapter argues further that African endogenous knowledge system encodes environmental management and policies for resource development in Africa’s complex and ageing ecological system. In doing this, we engage in conversation about current and potential land sovereignty work in African Indigenous communities. This will achieve food security and improved nutrition, promote sustainable agriculture and improved economic status of the African indigenous farmer. We conclude that, in seeking the whole from the units of the earth resources through cultivation of the soil, the African derives high credit balance of spiritual good, virtuous life, self-reliance, courage and moral integrity. (shrink)

We contrast reactive and endogenously active perspectives on brain activity. Both have been pursued continuously in neurophysiology laboratories since the early 20thcentury, but the endogenous perspective has received relatively little attention until recently. One of the many successes of the reactive perspective was the identification, in the second half of the 20th century, of the distinctive contributions of different brain regions involved in visual processing. The recent prominence of the endogenous perspective is due to new findings of ongoing (...) oscillatory activity in the brain at a wide range of time scales, exploiting such techniques as single-cell recording, EEG, and fMRI. We recount some of the evidence pointing to ways in which this endogenous activity is relevant to cognition and behavior. Our major objective is to consider certain implications of the contrast between the reactive and endogenous perspectives. In particular, we relate these perspectives to two different characterizations of explanation in the new mechanistic philosophy of science. In a basic mechanistic explanation, the operations of a mechanism are characterized qualitatively and as functioning sequentially until a terminating condition is realized. In contrast, a dynamic mechanistic explanation allows for non-sequential organization and emphasizes quantitative modeling of the mechanisms's behavior. For example, with appropriate parameter values a set of differential equations can be used to demonstrate ongoing oscillations in a system organized with feedback loops. We conclude that the basic conception of mechanistic explanation is adequate for reactive accounts of brain activity, but dynamical accounts are required to explain sustained, endogenous activity. (shrink)

We consider a two-player contest in which one contestant has a headstart advantage, but both can exert further effort. We allow the prize to depend on total performance in the contest and consider the respective cases in which efforts are productive and destructive of prize value. When the contest success function takes a logit form, and marginal cost is increasing in effort, we show that a Nash equilibrium exists and is unique both in productive and destructive endogenous prize contests. (...) In equilibrium, the underdog expends more resources to win the prize, but still his probability of winning remains below that of the favorite. In a productive contest, the underdog behaves more aggressively and wins the prize more often in comparison to a fixed-value contest. Thus, the degree of competitive balance—defined as the level of uncertainty of the outcome—depends upon the prize nature of the contest. (shrink)

A human retrovirus etiologically related to a unique leukemia, adult T‐cell leukemia, has been discovered. This retrovirus is endemic in certain areas and ethnic groups, such as the Japanese in Japan and Blacks in Africa. The virus is transmitted from mother to child and husband to wife and by blood transfusion. In addition, a virus like the human retrovirus has been found in various species of monkeys in Asia and Africa. This review describes and discusses recent results (...) on the natural history of these primate lymphotropic retroviruses. (shrink)

This paper examines the theoretical background and actual behavior in a gaming tournament with endogenous timing where a person has more incentive, structure, and time to form a strategy. The baseline treatment suggests that subgame perfection is a reasonable predictor of behavior –- subjects made 170 of 208 theoretically predicted choices of best actions, with the majority of mistakes made in timing choices by the players who did not survive the cut to the second round. Four sensitivity treatments established (...) that the design feature that lead to more predictable behavior was time to think –- 745 of 960 correctly predicted decisions with more time versus 595 of 960 with less time. A random effects Probit model suggests that the key design feature that closed the gap between predicted and observed behavior was not necessarily the non-linear payoffs created by the tournament design, but rather that the key was providing people with more time to think about their strategy. (shrink)

Through a series of examples, we illustrate some important drawbacks that the action model logic framework suffers from in its ability to represent the dynamics of information updates. We argue that these problems stem from the fact that the action model, a central construct designed to encode agents’ uncertainty about actions, is itself effectively common knowledge amongst the agents. In response to these difficulties, we motivate and propose an alternative semantics that avoids them by endogenizing the action model. We discuss (...) the relationship between this new framework and action model logic, and provide a sound and complete axiomatization of several new logics that naturally arise. (shrink)

In addition to endogenously produced opiates, which are part of normal affiliative neurocircuitry and attachment formation, exogenous opiates – such as drugs of addiction and abuse – may affect affiliation. We consider possible modulatory effects of such exogenous opiates on the development of early parent–infant attachment from both parents' and infants' perspectives.

Lowest-unique sealed-bid auctions are auctions with endogenous participation, costly bids, and the lowest bid among all unique bids wins. Properties of symmetric NEs are studied. The symmetric NE with the lowest expected gains is the maximin outcome under symmetric strategies, and it is the solution to a mathematical program. Comparative statics for the number of bidders, the value of the item and the bidding cost are derived. The two bidders’ auction is equivalent to the Hawk–Dove game. Simulations of replicator (...) dynamics provide numerical evidence that the symmetric NE with the lowest expected gains is also asymptotically stable. (shrink)

Does the desirability of social institutions for public goods provision depend on the extent to which they include mechanisms for endogenous enforcement of cooperative behavior? We consider alternative institutions that vary the use of direct punishments to promote social cooperation. In one institution, subjects participate in a public goods experiment in which an initial stage of voluntary contribution is followed by a second stage of voluntary, costly sanctioning. Another institution consists of the voluntary contribution stage only, with no subsequent (...) opportunity to sanction. In a third stage subjects vote for which institution they prefer for future interactions: do they prefer one that does allow sanctions or one that does not allow sanctions? Our results show that even though sanctions are frequently used when available, the clear majority of individuals vote for the institution that does not allow sanctions. Thus, a distinction is required between the principles that guide the choice of institutions and the principles that apply to actions guided by institutions. Our results indicate that it is the wealth generated by the institution that determines its desirability. (shrink)

In this paper, we study the auction to allocate an indivisible good when each potential buyer has a private and independent valuation for the item and suffers a negative externality if a competitor acquires it. In that case, the outside option of each buyer is mechanism-dependent, which implies that participation is endogenous. As several works in the literature have shown, the optimal auction entails strong threats to induce full entry and maximal expected revenue. This results from the full commitment (...) assumption, which ensures that threats are credible. We show that absent credible threats, the entry process does not lead to full participation: the equilibrium entails screening of agents in the entry stage and a trade-off between reserve prices and entry fees. Besides, we discuss the conditions under which the impossibility to use threats does not prevent the seller from ensuring a minimal screening and reaching a high expected revenue. (shrink)

In this paper, we analyse the simplest possible three-dimensional model of endogenous growth to account for the relationship between financial intermediation and economic growth. In our setting, households maximize an interim utility function and firms maximize profit. Households can save money only through banks which offer firms investment loans. We show that under very general assumptions, investments realized by firms depend not only on savings accumulated by banks but also on financial intermediation technology ϕ(θ). Using mathematical methods of dynamical (...) systems, we found stationary states of the system and study their stability. (shrink)

In this paper we suggest a model of sequential auctions with endogenous participation where each bidder conjectures about the number of participants at each round. Then, after learning his value, each bidder decides whether or not to participate in the auction. In the calculation of his expected value, each bidder uses his conjectures about the number of participants for each possible subgroup. In equilibrium, the conjectured probability is compatible with the probability of staying in the auction. In our model, (...) players face participation costs, bidders may buy as many objects as they wish and they are allowed to drop out at any round. Bidders can drop out at any time, but they cannot come back to the auction. In particular we can determine the number of participants and expected prices in equilibrium. We show that for any bidding strategy, there exists such a probability of staying in the auction. For the case of stochastically independent objects, we show that in equilibrium every bidder who decides to continue submits a bid that is equal to his value at each round. When objects are stochastically identical, we are able to show that expected prices are decreasing. (shrink)