Model-Based Wisdom of the Crowd for Sequential Decision-Making Tasks.

We study the wisdom of the crowd in three sequential decision-making tasks: the Balloon Analogue Risk Task (BART), optimal stopping problems, and bandit problems. We consider a behavior-based approach, using majority decisions to determine crowd behavior and show that this approach performs poorly in the BART and bandit tasks. The key problem is that the crowd becomes progressively more extreme as the decision sequence progresses, because the diversity of opinion that underlies the wisdom of the crowd is lost. We also consider model-based approaches to each task. This involves inferring cognitive models for each individual based on their observed behavior, and using these models to predict what each individual would do in any possible task situation. We show that this approach performs robustly well for all three tasks and has the additional advantage of being able to generalize to new problems for which there are no behavioral data. We discuss potential applications of the model-based approach to real-world sequential decision problems and discuss how our approach contributes to the understanding of collective intelligence.

A model-based analysis of the impairment of semantic memory.

We use cognitive models to evaluate three theories of the change in semantic memory caused by Alzheimer's disease. We use data from 14,096 clinical assessments of 3602 Alzheimer's patients and their caregivers. Each patient completed a semantic memory task involving the odd-one-out comparison of animal names. Each patient was also independently evaluated to determine their level of impairment. Our cognitive models assume a feature-based representation of the animals and odd-one-out choice probabilities based on common-feature similarities. We find no evidence for the restructured representation hypothesis, which claims that impairment causes changes in the features used to represent stimuli. We also find no evidence for the attention change hypothesis, which claims that impairment causes greater attention to be given to concrete features at the expense of more abstract features. We do find evidence for the noisy access hypothesis, which claims that odd-one-out choices become less determined by semantic similarity and more prone to the simple response strategy of choosing the last option. We conclude that the noisy access hypothesis provides a simple account of odd-one-out choice behavior throughout the progression of Alzheimer's disease. More elaborate theories involving changes to underlying mental representations and attention processes need to provide evidence they are superior to the noisy access account.

Visual search enhances subsequent mnemonic search.

We examined how the performance of a visual search task while studying a list of to-be-remembered words affects subsequent memory for those words by humans. Previous research had suggested that episodic context encoding is facilitated when the study phase of a memory experiment requires, or otherwise encourages, a visual search for the to-be-remembered stimuli, and theta-band oscillations are more robust when animals are searching their environment. Moreover, hippocampal theta oscillations are positively correlated with learning in animals. We assumed that a visual search task performed during the encoding of words for a subsequent memory test would induce an exploratory state that would mimic the one that is induced in animals when performing exploratory activities in their environment, and that the encoding of episodic traces would be improved as a result. The results of several experiments indicated that the performance of the search task improved free recall, but the results did not extend to yes-no or forced choice recognition memory testing. We propose that visual search tasks enhance the encoding of episodic context information but do not enhance the encoding of to-be-remembered words.