We introduce an algorithm that, given n objects, learns a similarity matrix
over all n^2 pairs, from crowdsourced data alone. The algorithm samples
responses to adaptively chosen triplet-based relative-similarity queries. Each
query has the form "is object 'a' more similar to 'b' or to 'c'?" and is chosen
to be maximally informative given the preceding responses. The output is an
embedding of the objects into Euclidean space (like MDS); we refer to this as
the "crowd kernel."
The process of consensus voting has many distinct advantages: it fosters
discussion and participation, empowers minorities and independent thinkers, and
is more likely, after a decision has been made, to secure the participants'
support for the chosen course of action.
We address the problem of fair division, or cake cutting, with the goal of
finding truthful mechanisms. In the case of a general measure space ("cake")
and non-atomic, additive individual preference measures - or utilities - we
show that there exists a truthful "mechanism" which ensures that each of the k
players gets at least 1/k of the cake. This mechanism also minimizes risk for
truthful players. Furthermore, in the case where there exist at least two
different measures we present a different truthful mechanism which ensures that
each of the players gets more than 1/k of the cake.
We propose a simple and efficient Bayesian model of iterative learning on
social networks. This model is efficient in two senses: the process both
results in an optimal belief, and can be carried out with modest computational
resources for large networks. This result extends Condorcet's Jury Theorem to
general social networks, while preserving rationality and computational
feasibility.
Arrow's theorem implies that a social choice function satisfying
Transitivity, the Pareto Principle (Unanimity) and Independence of Irrelevant
Alternatives (IIA) must be dictatorial. When non-strict preferences are
allowed, a dictatorial social choice function is defined as a function for
which there exists a single voter whose strict preferences are followed. This
definition allows for many different dictatorial functions. In particular, we
construct examples of dictatorial functions which do not satisfy Transitivity
and IIA.