Learning from Experts

The survey is concerned with the issue of information transmission from experts to non-experts. Two main approaches to the use of experts can be traced. According to the game-theoretic approach expertise is a case of asymmetric information between the expert, who is the better informed agent, and the non-expert, who is either a decision-maker or an evaluator of the expert’s performance. According to the Bayesian decision-theoretic approach the expert is the agent who announces his probabilistic opinion, and the non-expert has to incorporate that opinion into his beliefs in a consistent way, despite his poor understanding of the expert’s substantive knowledge. The two approaches ground the relationships between experts and non-experts on such different premises that their results are very poorly connected.Expert, Information Transmission, Learning

Repeated Cheap-Talk Games of Common Interest between a Decision-Maker and an Expert of Unknown Statistical Bias

Two agents are engaged in a joint activity that yields a common perperiod payoff at two rounds of play. The expert announces the probability that the current state of the world is low, instead of high, at each stage. Having received the report of the expert, the decision-maker takes action at every period according to his posterior beliefs. At the end of each round of play, the true current state is verifiable. The distinctive assumption of the paper is that the decision-maker makes a subjective appraisal of the expert’s reliability: he considers the expert’s true forecasts as the outcomes of an experiment of unknown statistical bias. The paper shows that the expert will have instrumental reputational concerns, related to the future estimate of the systematic error associated to his predictions. In contrast with previous work, reputational concerns are shown to enhance the credibility of the initial messages, and to increase both the agents’ expected payoff at the first round of play in equilibrium. The equilibrium messages will be noisy, but noisiness will be less costly than it would be in single-stage games.Opinion, Expert, Strategic Communication

A Role for Instructions

The paper is concerned with instructions as a way of setting premises for subsequent decisions in models of teams à la Marschak-Radner, under information diversification. The paper suggests that instructions can bridge people’s differences in knowledge: they do not require mutual understanding between the sender and the receiver as other forms of communication do. In particular, the knowledge of both the team payoff function and the team organisation can be ordered according to hierarchical ranks. First, the paper shows the equivalence between commands and communication in Marschak and Radner (1972). Second, it derives the requirements in terms of knowledge of the members that follow from given structures of task assignment, information diversification and message flows. Hierarchical ranks are shown to correspond to different degrees of intelligibility of the members with respect to the team operations.Instructions, Hierarchy, Knowledge, Decentralisation

Non-Uniqueness of Equilibria in One-Shot Games of Strategic Communication

The paper shows that Perfect Bayesian equilibria need not be unique in the strategic communication game of Crawford and Sobel (1982). First, different equilibrium partitions of the state space can have equal cardinality, despite fixed prior beliefs. Hence, there can be different equilibrium action profiles with the same size. Second, provided a Perfect Bayesian equilibrium exists, different message rules and beliefs can hold in other equilibria inducing the same action profile.Sender-Receiver Games, Strategic Information Transmission

"He who sets the boundary”. Chieftaincy as a “necessary” institution in modern Ghana

The title of this paper was inspired by an etymology formulated in 1929 by a famous Gold Coast maìtre-a-penser, J. de Graft Johnson. He explained the most common akan1 term for a chief ohene as a derivation from hye, boundary, with the meaning of “he who would decide the ohi (boundary) between the various groups farming on lands commonly reputed to be under his control” (de Graft Johnson, 1929). The ohene is therefore ‘the settler of the boundary’. Etymology is a tricky territory and I am not sure whether this interpretation is reliable. However it suits perfectly what I intend to say in my paper: 1) Controversial as Chieftaincy may be in Ghana, it is perhaps the clearest embodiment of shared concepts of what it means to belong to a place. 2) The link between Chieftaincy and place is not a static one. To a great extent chiefs have the power to redefine the very nature, size and scope of the place/locality they embody. 3) They are potentially in a better position to re-shape, manipulate, enlarge or shrink boundaries than most other player on the national stage. 4) From the early 1990s many of them were able to exercise that power to an extent they had not experienced since colonial days and in ways new to Ghanaian society and to themselves. I will try to substantiate my points through reference to a recent case of chieftaincy litigation in the Western Region of Ghana.

On the contribution of binocular disparity to the long-term memory for natural scenes

Binocular disparity is a fundamental dimension defining the input we receive from the visual world, along with luminance and chromaticity. In a memory task involving images of natural scenes we investigate whether binocular disparity enhances long-term visual memory. We found that forest images studied in the presence of disparity for relatively long times (7s) were remembered better as compared to 2D presentation. This enhancement was not evident for other categories of pictures, such as images containing cars and houses, which are mostly identified by the presence of distinctive artifacts rather than by their spatial layout. Evidence from a further experiment indicates that observers do not retain a trace of stereo presentation in long-term memory