When individuals independently recollect events or retrieve facts from memory, how can we aggregate these retrieved memories to reconstruct the actual set of events or facts? In this research, we report the performance of individuals in a series of general knowledge tasks, where the goal is to reconstruct from memory the order of historic events, or the order of items along some physical dimension. We introduce two Bayesian models for aggregating order information based on a Thurstonian approach and Mallows model. Both models assume that each individuals reconstruction is based on either a random permutation of the unobserved ground truth, or by a pure guessing strategy. We apply MCMC to make inferences about the underlying truth and the strategies employed by individuals. The models demonstrate a wisdom of crowds" effect, where the aggregated orderings are closer to the true ordering than the orderings of the best individual."

We present a computational Bayesian approach for Wiener diffusion models, which are prominent accounts of response time distributions in decision-making. We first develop a general closed-form analytic approximation to the response time distributions for one-dimensional diffusion processes, and derive the required Wiener diffusion as a special case. We use this result to undertake Bayesian modeling of benchmark data, using posterior sampling to draw inferences about the interesting psychological parameters. With the aid of the benchmark data, we show the Bayesian account has several advantages, including dealing naturally with the parameter variation needed to account for some key features of the data, and providing quantitative measures to guide decisions about model construction.

We apply a minimum description length-based clustering technique to the problem of partitioning a set of learning curves. The goal is to partition experimental data collected from different sources into groups of sources that are statistically the same. We solve this problem by defining statistical models for the data generating processes, then partitioning them using the normalized maximum likelihood criterion. Unlike many alternative model selection methods, this approach is optimal (in a minimax coding sense) for data of any sample size. We present an application of the method to the cognitive modeling problem of partitioning of human learning curves for different categorization tasks.

This paper develops a new representational model of similarity data that combines continuous dimensions with discrete features. An al- gorithm capable of learning these representations is described, and a Bayesian model selection approach for choosing the appropriate number of dimensions and features is developed. The approach is demonstrated on a classic data set that considers the similarities between the numbers 0 through 9.

A transformational approach to visual perception is presented, in which image structure is encoded in the parameters of those transformations that produce an output maximally symmetric with the current input. Results are presented for a computer program, dubbed SMART (Symmetry Maximizing Array using Random Transformations). SMART consists of a parallel array of independent symmetry detectors. Each detector attempts to find a transformation that maximizes the symmetry between the original and the transformed configuration. The weighted output of the detectors is collated in a connection matrix, which summarizes the image structure and provides a continuously-varying measure of relative symmetry. The program is applied to constrained and random arrays, Glass (1969) figures and the detection of hidden symmetric targets. More general implications are briefly discussed.

The common neural network modeling practice of representing the elements of a task domain in terms of a set of features lacks justification if the features are derived through some form of ad hoc preabstraction. By examining a featural similarity model related to established multidimensional scaling techniques, a neural network is developed that generates features from similarity data and attaches weights to these features. The network performs a constrained search of a continuous solution space to determine the features and uses a previously developed regularization technique to minimize the number of features it derives. The network is demonstrated on artificial data, from which it recovers known features and weights, and on two real data sets involving the similarity of a set of geometric shapes and the abstract conceptual similarities of the 10 Arabic numerals. On the basis of these results, the relationship between the multidimensional scaling approach adopted by the network and an alternative additive clustering approach to feature extraction is discussed.

The application of connectionist learning procedures to the development of psychological internal representations requires a constraining theory of mental structure. The psychological space construct is advanced for this role and, consequently, a connectionist network which learns the multi-dimensionally scaled representations of a set of stimuli is developed. The model assumes that the function relating similarity to distance in psychological space is an exponential decay function, operates under the family of Minkowskian metrics and is able to determine the appropriate dimensionality of the psychological spaces it derives. The model is demonstrated on both separable and integral stimuli, and the validity of its application of gradient descent optimization principles over the city-block metric is examined. Several modelling extensions are discussed, including means by which the model might learn more general psychophysical mappings, and be able to derive internally the measures of psychological similarity currently provided through a similarity matrix.