All existing impossibility theorems on judgment aggregation over logically connected propositions have one of two restrictions: they either use a controversial systematicity condition or apply only to special agendas of propositions with rich logical connections. An important open question is...

It is known that majority voting among several individuals on logically interconnected propositions may generate irrational collective judgments. We generalize majority voting by considering quota rules, which accept each proposition if and only if the number of individuals accepting it exceeds...

In response to recent work on the aggregation of individual judgements on logically connected propositions into collective judgements, it is often asked whether judgement aggregation is a special case of Arrowian preference aggregation. We argue the opposite. After proving a general...

In the emerging literature on judgment (as opposed to preference) aggregation, expert rights or liberal rights have not been investigated yet. When a group forms collective beliefs, it may assign experts with special knowledge on certain propositions the right to determine the collective...

In the theory of judgment aggregation on connected propositions, an important question remains open: Which aggregation rules are manipulable and which are strategy-proof? We define manipulability and strategy- proofness in judgment aggregation, characterize all strategy-proof aggregation rules,...

It is known that, in Condorcet’s classical model of jury decisions, the proportion of jurors supporting a decision is not a significant indicator of that decision’s reliability: the probability that a particular majority decision is correct given the size of the majority depends only on the...

A “framing” effect occurs when an agent’s choices are not invariant under changes in the way a choice problem is formulated, e.g. changes in the way the options are described (violation of description invariance) or in the way preferences are elicited (violation of procedure invariance)....

May's theorem famously shows that, in social decisions between two options, simple majority rule uniquely satisfies four appealing conditions. Although this result is often cited as a general argument for majority rule, it has never been extended beyond pairwise decisions. Here we generalize...

Consider the hypothesis H that a defendant is guilty (a patient has condition C), and the evidence E that a majority of h out of n independent jurors (diagnostic tests) have voted for H and a minority of k:=n-h against H. How likely is the majority verdict to be correct? By a formula of...

If each member of a group assigns a certain probability to a hypothesis, what probability should the collective as a whole assign? More generally, how should individual probability functions be merged into a single collective one? I investigate this question in case that the individual...