A Trackable Model of Reciprocity and Fairness.

We introduced a parametric model of other-regarding preferences in which my emotional state determines the marginal rate of substitution between my own and other' payoffs, and thus my subsequent choices. In turn, my emotional state responds to relative status and to the kindness or unkindness of others' choices. Structural estimations of this model with six existing data sets demonstrate that other-regarding preferences depend on status, reciprocity, and perceived property rights.RECIPROCITY ; MARGINAL RATE OF SUBSTITUTION ; PAYOFFS

The Competitive Market Paradox.

The competitive market model is a paradoxical. In perfect competition, agents cannot influence price: they only select an output quantity. Such passive behavior doesn’t conform to the intuitive notion of competition. This paper describes an experiment which demonstrates that near or even at a competitive equilibrium price, competition is undiminished. A substantial difference between the performance of sellers and buyers frequently results from this vigorous competition, even with low price variability and approximate efficiency. In double auction experiment sessions conducted with both automated and human agents, exogenous variation of the pace of asks and bids of automated agents demonstrates that the performance difference between sellers and buyers results primarily from a difference between the pace of asks and bids. If the buyers’ pace is slower than sellers’ pace, buyers make price concessions less frequently than sellers so that prices move below the equilibrium price. Then more buyers become active and fewer sellers remain active. Prices stabilize when changes to the numbers of active buyers and sellers offset the superior bargaining capability of one side or the other. In competitive equilibrium, to a first approximation agents are price takers, but that doesn’t preclude vigorous competition: competitive behavior moves to the dimension of bargaining pace.Bargaining ; bounded rationality ; competitive equilibrium ; double auction ; experimental economics

Individual Rationality and Market Efficiency

Smith’s (1962) demonstration that prices and allocations quickly converge to the competitive equilibrium in the continuous double auction (CDA) remains one of the most important results in experimental economics. Market experiments and exchange models have added considerably to our knowledge of how markets reach equilibrium, and how they respond to disruptions. Perhaps the best-known model of exchange in CDA market experiments is the random behavior “zero-intelligence” (ZI) model by Gode and Sunder (1993). They argue that the CDA generates efficient allocations and “convergence of transaction prices to the proximity of the theoretical equilibrium price,” provided only that agents meet their budget constraints. We demonstrate that prices do not converge in their simulations. Their budget constraint requires that a buyer’s currency never exceeds her commodity value, which is an unnatural restriction. Their conclusion that market efficiency results from the structure of the CDA independent of traders’ profit seeking behavior rests on their claim that the constraints that they impose are a part of the market institution. We show that actually they impose individual rationality. Misinterpretation of this behavioural constraint has lead to unproductive debate on market adjustment processes

T cell specific adaptor protein (TSAd) promotes interaction of Nck with Lck and SLP-76 in T cells

Background: The Lck and Src binding adaptor protein TSAd (T cell specific adaptor) regulates actin polymerization in T cells and endothelial cells. The molecular details as to how TSAd regulates this process remain to be elucidated. Results: To identify novel interaction partners for TSAd, we used a scoring matrix-assisted ligand algorithm (SMALI), and found that the Src homology 2 (SH2) domain of the actin regulator Non-catalytic region of tyrosine kinase adaptor protein (Nck) potentially binds to TSAd phosphorylated on Tyr280 (pTyr280) and pTyr305. These predictions were confirmed by peptide array analysis, showing direct binding of recombinant Nck SH2 to both pTyr280 and pTyr305 on TSAd. In addition, the SH3 domains of Nck interacted with the proline rich region (PRR) of TSAd. Pull-down and immunoprecipitation experiments further confirmed the Nck-TSAd interactions through Nck SH2 and SH3 domains. In line with this Nck and TSAd co-localized in Jurkat cells as assessed by confocal microscopy and imaging flow cytometry. Co-immunoprecipitation experiments in Jurkat TAg cells lacking TSAd revealed that TSAd promotes interaction of Nck with Lck and SLP-76, but not Vav1. TSAd expressing Jurkat cells contained more polymerized actin, an effect dependent on TSAd exon 7, which includes interactions sites for both Nck and Lck. Conclusions: TSAd binds to and co-localizes with Nck. Expression of TSAd increases both Nck-Lck and Nck-SLP-76 interaction in T cells. Recruitment of Lck and SLP-76 to Nck by TSAd could be one mechanism by which TSAd promotes actin polymerization in activated T cells. © 2015 Hem et al

Adaptive-Aggressive Traders Don't Dominate

For more than a decade Vytelingum's Adaptive-Aggressive (AA) algorithm has been recognized as the best-performing automated auction-market trading-agent strategy currently known in the AI/Agents literature; in this paper, we demonstrate that it is in fact routinely outperformed by another algorithm when exhaustively tested across a sufficiently wide range of market scenarios. The novel step taken here is to use large-scale compute facilities to brute-force exhaustively evaluate AA in a variety of market environments based on those used for testing it in the original publications. Our results show that even in these simple environments AA is consistently out-performed by IBM's GDX algorithm, first published in 2002. We summarize here results from more than one million market simulation experiments, orders of magnitude more testing than was reported in the original publications that first introduced AA. A 2019 ICAART paper by Cliff claimed that AA's failings were revealed by testing it in more realistic experiments, with conditions closer to those found in real financial markets, but here we demonstrate that even in the simple experiment conditions that were used in the original AA papers, exhaustive testing shows AA to be outperformed by GDX. We close this paper with a discussion of the methodological implications of our work: any results from previous papers where any one trading algorithm is claimed to be superior to others on the basis of only a few thousand trials are probably best treated with some suspicion now. The rise of cloud computing means that the compute-power necessary to subject trading algorithms to millions of trials over a wide range of conditions is readily available at reasonable cost: we should make use of this; exhaustive testing such as is shown here should be the norm in future evaluations and comparisons of new trading algorithms.Comment: To be published as a chapter in "Agents and Artificial Intelligence" edited by Jaap van den Herik, Ana Paula Rocha, and Luc Steels; forthcoming 2019/2020. 24 Pages, 1 Figure, 7 Table

Q-Strategy: A Bidding Strategy for Market-Based Allocation of Grid Services

The application of autonomous agents by the provisioning and usage of computational services is an attractive research field. Various methods and technologies in the area of artificial intelligence, statistics and economics are playing together to achieve i) autonomic service provisioning and usage of Grid services, to invent ii) competitive bidding strategies for widely used market mechanisms and to iii) incentivize consumers and providers to use such market-based systems. The contributions of the paper are threefold. First, we present a bidding agent framework for implementing artificial bidding agents, supporting consumers and providers in technical and economic preference elicitation as well as automated bid generation by the requesting and provisioning of Grid services. Secondly, we introduce a novel consumer-side bidding strategy, which enables a goal-oriented and strategic behavior by the generation and submission of consumer service requests and selection of provider offers. Thirdly, we evaluate and compare the Q-strategy, implemented within the presented framework, against the Truth-Telling bidding strategy in three mechanisms – a centralized CDA, a decentralized on-line machine scheduling and a FIFO-scheduling mechanisms

Structure function analysis of SH2D2A isoforms expressed in T cells reveals a crucial role for the proline rich region encoded by SH2D2A exon 7

BACKGROUND: The activation induced T cell specific adapter protein (TSAd), encoded by SH2D2A, interacts with and modulates Lck activity. Several transcript variants of TSAd mRNA exist, but their biological significance remains unknown. Here we examined expression of SH2D2A transcripts in activated CD4+ T cells and used the SH2D2A variants as tools to identify functionally important regions of TSAd. RESULTS: TSAd was found to interact with Lck in human CD4+ T cells ex vivo. Three interaction modes of TSAd with Lck were identified. TSAd aa239–256 conferred binding to the Lck-SH3 domain, whereas one or more of the four tyrosines within aa239–334 encoded by SH2D2A exon 7 was found to confer interaction with the Lck-SH2-domain. Finally the TSAd-SH2 domain was found to interact with Lck. The SH2D2A exon 7 encoding TSAd aa 239–334 was found to harbour information essential not only for TSAd interaction with Lck, but also for TSAd modulation of Lck activity and translocation of TSAd to the nucleus. All five SH2D2A transcripts were found to be expressed in CD3 stimulated CD4+ T cells. CONCLUSION: These data show that TSAd and Lck may interact through several different domains and that Lck TSAd interaction occurs in CD4+ T cells ex vivo. Alternative splicing of exon 7 encoding aa239–334 results in loss of the majority of protein interaction motives of TSAd and yields truncated TSAd molecules with altered ability to modulate Lck activity. Whether TSAd is regulated through differential alternative splicing of the SH2D2A transcript remains to be determined

Automated Negotiation in Many-to-Many Markets for Imperfectly Substitutable Goods

In this paper, we present an agent which is able to negotiate the buying and selling of imperfectly sustitutable goods in a double auction style market. Two goods are said to be imperfectly substitutable if a buyer can use either of them, but prefers one over the other. For example, an electronics manufacturer using a RAM chip can use many suppliers to do this but may be willing to pay a premium for components with a lower failure rate. We give a formal description of a double-auction style market mechanism for trading such goods, and define the (classical) equilibrium in such an environment. We present the IS-ZIP agent, which is a generalisation of the ZIP agent for double auctions of Cli# and Bruten [3]. It is able to participate in our double auction environment to make purchases or sales of imperfectly substitutable goods. We demonstrate that, when trading a single good, it is equivalent to Preist and van Tol's modification of the ZIP agent [11]. We describe experiments where a group of IS-ZIP agents with di#erent valuations trade repeatedly, and demonstrate that they rapidly converge to our predicted equilibrium. We conclude by relating our work to that of others, particulary work dealing with multi-attribute negotiation, and discussing extensions

Learning to trade in an unbalanced market

We study the evolution of trading strategies in double auctions as the size of the market gets larger. When the number of buyers and sellers is balanced, Fano et al.~(2011) show that the choice of the order-clearing rule (simultaneous or asynchronous) steers the emergence of fundamentally different strategic behavior. We extend their work to unbalanced markets, confirming their main result as well as that allocative inefficiency tends to zero. On the other hand, we discover that convergence to the competitive outcome takes place only when the market is large and that the long side of the market is more effective at improving its disadvantaged terms of trade under asynchronous order-clearing

How do markets manage water resources? An experiment

We experimentally test how a private monopoly, a duopoly and a public utility allocate water of differing qualities to households and farmers. Most of our results are in line with the theoretical predictions. Overexploitation of the resources is observed independently of the market structure. Stock depletion for the public utility is the fastest, followed by the private duopoly and private monopoly. On the positive aspects of centralized public management, we find that the average quality to price ratio offered by the public monopoly is substantially higher than that offered by the private monopoly or duopoly