Exemplar-memory and adaptive network models were compared in application to category learning data, with special attention to base rate effects on learning and transfer performance. Subjects classified symptom charts of hypothetical patients into disease categories, with informative feedback on learning trials and with the feedback either given or withheld on test trials that followed each fourth of the learning series. The network model proved notably accurate and uniformly superior to the exemplar model in accounting for the detailed course of learning; both the parallel, interactive aspect of the network model and its particular learning algorithm contribute to this superiority. During learning, subjects' performance reflected both category base rates and feature (symptom) probabilities in a nearly optimal manner, a result predicted by both models, though more accurately by the network model. However, under some test conditions, the data showed substantial base-rate neglect, in agreement with Gluck and Bower (1988b).

What is the socially optimal level of liquidity in a retirement savings system? Liquid retirement savings are desirable because liquidity enables agents to flexibly respond to preretirement events that raise the marginal utility of consumption, like income shocks. 1 On the other hand, preretirement liquidity is undesirable when it leads to undersaving arising from, for example, planning mistakes or self-control problems. 2

This study evaluated the impact of the modality of distractor tasks and the difficulty of the driving task on driver control over a vehicle. Driving is a task with a close link between visual information processing and driver performance variables such as lane keeping. Consequently, compared to auditory distractors, visual distractors should have a larger negative effect on vehicle control, but mainly when the driving task also adds significant workload for the driver. In this study, drivers drove around either a curvy or a straight track while occasionally performing either an auditory or a visual secondary monitoring task. Performance of the secondary task was associated with deterioration in steering wheel control and lane keeping, but only on the curvy track and mainly when the secondary task required visual monitoring. These results are discussed in terms of their implication for developing workload managers in in-vehicle driver support systems.

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We compare the liquidity that six developed countries have built into their employer-based defined contribution (DC) retirement schemes. In Germany, Singapore, and the UK, withdrawals are essentially banned no matter what kind of transitory income shock the household realizes. By contrast, in Canada and Australia, liquidity is state-contingent. For a middle-income household, DC accounts are completely illiquid unless annual income falls substantially, in which case DC assets become highly liquid. The US stands alone in the universally high liquidity of its DC system: whether or not income falls, the penalties for early withdrawal are low or non-existent.