Shyam Sunder, Yale University

Experiments with Minimally Intelligent Agents and Minimal Institutions: Structure and Behavior
Shyam Sunder, Yale University Barcelona LeeX Experimental Economics Summer School in Macroeconomics Universitat Pompeu Fabra Barcelona, June 14, 2014

Humanities and Science
Science does not know its debt to imagination. Ralph Waldo Emerson Vivisection is a social evil because if it advances human knowledge, it does so at the expense of human character. George Bernard Shaw The theoretical broadening which comes from having many humanities subjects on the campus is offset by the general dopiness of the people who study these things. Richard P. Feynman (Nobel Laureate in Physics) Economics has an amazing capacity to summarize staggeringly complex phenomena by the application of only a handful of principles Charles R. Plott 7/22/2018 Sunder, Structure and Behavior

Sunder, Structure and Behavior
Overview Origin of experimental economics in examination of aggregate phenomena Gradual, steady shift towards micro-levels due to Analytical process and reasoning Incremental research questions Unlike assumption in theory, people do not optimize well by intuition Today, much experimental work has shifted to examination of individual behavior and of economies populated by artificial agents Shift to individual behavior has accentuated the ever-present dilemma of social sciences in trying to be a science on one hand, and handle humans at the same time What are the antecedents and consequences of this trend? Usefulness of organizing experimental economics into three streams: Structural: macro properties of social structures Behavioral: behavior of individuals, and Agent-based: exploration of links between the micro and macro phenomena At least the structural part of economics can be firmly rooted in the tradition of sciences, bypassing the free-will dilemma of social sciences 7/22/2018 Sunder, Structure and Behavior

Examining Market Institutions
Chamberlin (1948) examined the behavior of a market institution under controlled conditions of his classroom Vernon Smith (1962), a subject of Chamberlin) redesigned and systematically varied the market conditions to examine price, allocation, and extraction of surplus Both designs deviated significantly from Walrasian tatonnement abstraction; they fleshed them out with details, using stock market as a guide Economic environment (market demand and supply) and market design as independent variables Market level outcomes as dependent variables 7/22/2018 Sunder, Structure and Behavior

Data from Experiments Experiments can yield a great deal of data Data are limited only by interest and imagination of the experimenter, and ingenuity in capturing data without distracting subjects from their task in a significant way Chamberlin gathered three pieces of data for each transaction (price, seller cost and buyer value), and the transaction sequence Examples of data he did not gather: the clock time of transactions, details of the bargaining process (time elapsed, price proposals, number of proposals, number of counter-parties bargained with), etc. 7/22/2018 Sunder, Structure and Behavior

Data to Meet Experimental Goals
Most experiments can yield a great deal of data We gather only what we need in order to address the question(s) we wish to answer on the basis of the experiment Constraints: Technology of data gathering, eased by development of computer technology to conduct economics experiments) The possibility of interaction between data capture and subjects Given Chamberlin’s goals, asking subjects to report their transactions immediately after they completed each transaction served his purposes well, causing little interference with subjects’ trading 7/22/2018 Sunder, Structure and Behavior

Shift Towards Micro Phenomena
Focus of experimental economics has gradually shifted from aggregate market level phenomena towards individual behavior Three factors seem to drive this shift The logic of analytical method Incremental research designs Empirical finding that people, acting by intuition alone, are not good at optimization as typically assumed in derivation of equilibria in economic theory 7/22/2018 Sunder, Structure and Behavior

Logic of Analytical Method
It is rare for the correspondence between the predictions of the relevant theory, and experimental data, to be nil or total If the experimenter has no or low expectation of correspondence between the two, observation of even a moderate relationship is seen as half full glass of water However, most experiments are designed to examine specific theories that have some legitimate prior claim to predictive power In such situations, any imperfections of correspondence between data and theory are seen as half empty, not half full, glass of water Seeking a fuller explanation to close the gap between data and theory is a natural reaction of most investigators 7/22/2018 Sunder, Structure and Behavior

Search for Higher Explanatory Power
Following this logic, analysis and discussion of most experiments ends in a search for ways to increase the correspondence between data and theory Better prediction and explanation is the currency of scientific progress We look for ways to modify the model to enhance its explanatory power through analysis—breaking the problem down into progressively smaller components This logical pursuit shifts research question(s) to the next level of detail causing “micro-nization” of economics Discarding the details, to step back and see the big picture, is a less common reaction 7/22/2018 Sunder, Structure and Behavior

Demand, Supply and Experiments
Simple economic theory: point of intersection of demand and supply determines price and allocations Economists’ deep faith in theory Neither Chamberlin’s nor Smith’s data corresponded precisely to the theory Smith saw half full glass of water, while Chamberlin saw the half empty part and set out to build a model to better explain the residual variation left unexplained by the simple demand-supply model (instantaneous demand/supply) 7/22/2018 Sunder, Structure and Behavior

Chamberlin (1948), Figure 3 7/22/2018 Sunder, Structure and Behavior

Smith (1962) Chart 1 7/22/2018 Sunder, Structure and Behavior

Incremental Research Designs
A good part of our research (including experimental) is incremental, originating in proposals to gather data about some additional aspect of behavior, or additional analysis of existing data We make conjectures about how such data or analysis might help explain residual variation Incremental work dominates graduate seminars focused on critique and replication of extant work Easy to think of additional observations, motivations, and information conditions associated with individual participants to improve the fit between data and model 7/22/2018 Sunder, Structure and Behavior

Change in Models and Questions
Both analytical logic and incremental pursuits change the model used Additional variables use up some degrees of freedom, but observations at micro-level are far more numerous than at macro-level Shift to micro level also changes the research question(s) being asked “Why is the price equal x?” might be replaced by “why did trader y bid z?” 7/22/2018 Sunder, Structure and Behavior

Individual Behavior and the Dilemma of Social Sciences
This shift towards micro-behavior confronts economics with a fundamental dilemma shared among the social sciences As a science, we seek general laws that apply everywhere at all time, emulating physics, chemistry and biology Perfecting the scope and power of general laws of human behavior also implies squeezing out the essence of humanity—our free will What does it mean to have a science of individual human behavior? 7/22/2018 Sunder, Structure and Behavior

Free Will Free will, independent thinking, and ability to choose are essential to our concept of self We believe in our power and ability to do what we wish, beyond what is predictable on the basis of our circumstances, beliefs, and tendencies Ability to rise above our circumstances as the essence of human identity We can choose deliberately, in ways unpredictable to others Else, we would slip to the status we assign to animals, plants and inanimate objects 7/22/2018 Sunder, Structure and Behavior

Humanities: Eternal Truths
Humanities celebrate infinite variety of human behavior, but no laws of behavior In epics and literature: eternal verities, but no laws of behavior Epics (Mahabharata, Iliad) Duryodhana, Yudhishtira, Arjuna Literature (Dante’s Inferno, Shakespeare’s Hamlet) Human truths, questions, and tendencies repeated through history, always with a new twist People choose in ways unpredictable on the basis of their circumstances Celebration of infinite variation in human nature 7/22/2018 Sunder, Structure and Behavior

Science: Eternal Laws Identifying laws of nature valid everywhere and all the time Essence: regularities of nature captured in known and knowable relationships among observable elements (including stochastic) Helps understand, explain, and predict If I know X, can I form a better idea of whether Y was, is or will be? Objects of science have no free will A photon does not pause to enjoy the scenery A marble rolling down the side of a bowl does not wonder about how hot the oil at the bottom is 7/22/2018 Sunder, Structure and Behavior

Social Science: Irresistible Force Meets Immovable Object
Free will essential to our concept of self Without the freedom to act, we would be no different than a piece of rock Yet, the object of study in social science is us As a science, it must look for eternal laws that apply to humanity But stripped of freedom to act, and subject to such laws, there can be no humanity 7/22/2018 Sunder, Structure and Behavior

Mismatch of Science and Personal Responsibility
Objects of science can have no personal responsibility They do not choose to do anything They are merely driven by their circumstances, like a piece of paper blown by gusts of wind, or a piece of rock rolling down the hill under force of gravity in the path of an oncoming car Or, perhaps an abused child who grows up to be an abusive parent, sans personal responsibility Science and personal responsibility do not mix well 7/22/2018 Sunder, Structure and Behavior

Neither Fish Nor Fowl This problem of social science is exemplified in the continuing attempts to build a theory of choice From science end: axiomatization of human choice as a function of innate preferences. People choose what they prefer How do we know what they prefer? Look at what they choose The circularity between preferences and choice might be avoided if there were permanency and consistency in preference-choice relationship across diverse contexts One could observe choice in one context, tentatively infer the preferences from these observations, and assuming consistent preferences, predict choice in other contexts Unfortunately, half-a-century of research has yielded little predictability of choice from inferred preferences across contexts (Friedman and Sunder 2004) Individual human behavior appears to be unmanageably rowdy for scientists to capture in a stable set of laws While humanists may not take delight at such disappointments, but they can hardly be surprised (if they pay any attention to choice theory) 7/22/2018 Sunder, Structure and Behavior

Dilemma of Social Science
Do we abandon free will, personal responsibility, and special human identity; and treat humans like other objects of science? That is, drop the “social” and become a plain vanilla science Or, do we abandon the search for universal laws, embrace human free will and unending variation of behavior, and join the humanities Either way, there will be no social science left Is there a way to keep “social” and “science” together in social science? 7/22/2018 Sunder, Structure and Behavior

Isolating Three Streams of Work
Perhaps there is no general solution to this dilemma The dilemma does, however, point to the potential value of isolating streams of work where it may be more or less of a problem Significant parts of social sciences, and a large part of economics, are concerned with aggregate level outcomes of socio-economic institutions Institutions themselves do not need to be ascribed intentionality or free will Characteristics of the institutions can be analyzed by methods of science without running into these dilemmas This will leave analysis of individual behavior in the territory between science and humanities Agent-based models (in economics and elsewhere) could serve the bridging function between aggregate and individual phenomena Let us consider these possibilities 7/22/2018 Sunder, Structure and Behavior

Individuals I do not have much to add on the most complex problem of examining individual behavior It seems that we shall continue to examine ourselves and our behavior using both humanities as well as science perspectives, without ever reconciling the two into a single logical structure There seems to be no way out 7/22/2018 Sunder, Structure and Behavior

Institutions Experimental economics started out as investigation of aggregate level outcomes of market institutions using human subjects Attention has gradually shifted from aggregate outcomes to micro behavior Logic of analytical approach Incremental research designs A third reason is that predictions of aggregate outcomes (equilibrium analysis) are typically made assuming optimization by individuals Cognitive psychology showed that individuals are not very good at optimization by intuition This mismatch between the optimization assumption actual behavior at individual level has given additional impetus to “micro-nization” of experimental economics Thanks to recent findings using agent-based methods, we can conduct the study of social-economic institutions using methods of science 7/22/2018 Sunder, Structure and Behavior

Optimization and Equilibrium
The standard approach of economic analysis has been to assume that individuals choose actions by optimizing given their preferences, information and opportunity sets Interaction of individual actions in the context of institutional rules yield outcomes (e.g., prices and allocations), equilibrium outcomes being of special interest Equilibrium predictions derived from assuming individual rationality could be suspect when such rationality assumption is not valid Agent-based simulations suggest that individual rationality can be sufficient but not necessary for attaining equilibria in the context of specific market institutions 7/22/2018 Sunder, Structure and Behavior

What Makes the Difference
7/22/2018 Sunder, Structure and Behavior

Why Equilibrium without Individual Optimization
Why do the markets populated with simple budget-constrained random bid/ask strategies converge close to Walrasian prediction in price and allocative efficiency No memory, learning, adaptation, maximization, even bounded rationality Search for programming and system errors did not yield fruit Modeling and analysis supported simulation results 7/22/2018 Sunder, Structure and Behavior

Inference Perhaps it is the structure, not behavior, that accounts for the first order magnitude of outcomes in competitive settings Computers and experiments with simple agents opened a new window into a previously inaccessible aspect of economics Ironically, it was not through computers’ celebrated optimization capability Instead, through deconstruction of human behavior Isolating the market level consequences of simple or arbitrarily chosen classes of individual behavior modeled as software agents 7/22/2018 Sunder, Structure and Behavior

Optimization Principle
In physics: marbles and photons “behave” but are not attributed any intention or purpose Yet, optimization principle has proved to be an excellent guide to how physical and biological systems as a whole behave At multiple hierarchical levels--brain, ganglion, and individual cell—physical placement of neural components appears consistent with a single, simple goal: minimize cost of connections among the components. The most dramatic instance of this "save wire" organizing principle is reported for adjacencies among ganglia in the nematode nervous system; among about 40,000,000 alternative layout orderings, the actual ganglion placement in fact requires the least total connection length. In addition, evidence supports a component placement optimization hypothesis for positioning of individual neurons in the nematode, and also for positioning of mammalian cortical areas. (Makes you wonder what went wrong with human design when you see all the biases and incompetence of human cognition. Could it be just the wrong benchmark?) Questions about “forests” and questions about “trees” 7/22/2018 Sunder, Structure and Behavior

Optimization Principle Imported into Economics
Humans and human systems as objects of economic analysis Conflict between mechanical application of optimization principle and our self-esteem (free will) Optimization principle interpreted as a behavioral principle, shifting focus from aggregate to individual behavior Cognitive science: we are not good at optimizing Willingness among economists to abandon the optimization principle 7/22/2018 Sunder, Structure and Behavior

Dropping the “Infinite Faculties” Assumption
Conlisk: Empirical evidence in favor of bounded rationality Empirical evidence on importance of bounded rationality Proven track record of bounded rationality models (in explaining individual behavior) Unconvincing logic of unbounded rationality All these reasons focus on the “trees” not “forest” 7/22/2018 Sunder, Structure and Behavior

Equilibrium and Simon Simon in the third edition of The Sciences of the Artificial wrote: “This skyhook-skyscraper construction of science from the roof down to the yet unconstructed foundations was possible because the behavior of the system at each level depended on only a very approximate, simplified, abstracted characterization of the system at the level next beneath. This is lucky, else the safety of bridges and airplanes might depend on the correctness of the ‘Eightfold Way’ of looking at elementary particles.” Indeed, the powerful results of economic theory were derived from “a very approximate, simplified, abstracted characterization of the system at the level next beneath,”—the economic man so maligned, and its scientific purpose and role so misunderstood, by many who claim to be followers of Simon 7/22/2018 Sunder, Structure and Behavior

Economics: Structural or Behavioral
Economics can be usefully thought of as a behavioral science in the sense physicists study the “behavior” of marbles and photons Given the pride we take in attributing the endowment of free will to ourselves, this interpretation of behavior is a hard sell in social sciences To build on the achievements of theory, it may be better if we think of optimization in economics as a structural principle, Just as physicists (and many biologists) do This will allow us to focus on structural stream of economics in the tradition of sciences Individual behavior is likely to remain as a shared domain of humanities and sciences Modeling specific behaviors as software agents in the context of specific economic institutions allows us to make conditional statements about the links between individual and aggregate level phenomena (as in the case of ZI agents) 7/22/2018 Sunder, Structure and Behavior

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