The temporal selectivity of additive factor effects on the reaction process revealed in ERP component latencies

An experiment was conducted to relate individual components of the event-related brain potential to specific stages of information processing in a two-choice reaction time (RT) task in a group of undergraduate students. Specifically, the latency of the P300 component and the lateralized readiness potential (LRP) were studied as a function of variations in stimulus degradation and response complexity. It was hypothesized that degrading the stimulus would delay the P300 and LRP to the same extent as RT, and that increasing response complexity would affect RT but not P300 latency. The extant literature did not permit any hypothesis regarding the effect of response complexity on LRP latency. The two task variables were found to have additive effects on RT. As predicted, variations in stimulus degradation influenced the latencies of both components, whereas alterations in response complexity had no effect on P300 latency. A significant new finding was that the onset latency of the LRP remained unchanged across levels of response complexity. The overall pattern of results supports the notion of temporal selectivity of stage manipulations that is derived from discrete stage models of human information processing. Furthermore, these results refine the functional interpretation of the LRP by indicating that within the conceptual framework of a stage model the processes this component indexes succeed the start of response choice but precede the start of motor programming.     

Mental models and probabilistic thinking

This paper outlines the theory of reasoning based on mental models, and then shows how this theory might be extended to deal with probabilistic thinking. The same explanatory framework accommodates deduction and induction: there are both deductive and inductive inferences that yield probabilistic conclusions. The framework yields a theoretical conception of strength of inference, that is, a theory of what the strength of an inference is objectively: it equals the proportion of possible states of affairs consistent with the premises in which the conclusion is true, that is, the probability that the conclusion is true given that the premises are true. Since there are infinitely many possible states of affairs consistent with any set of premises, the paper then characterizes how individuals estimate the strength of an argument. They construct mental models, which each correspond to an infinite set of possibilities (or, in some cases, a finite set of infinite sets of possibilities). The construction of models is guided by knowledge and beliefs, including lay conceptions of such matters as the “law of large numbers”. The paper illustrates how this theory can account for phenomena of probabilistic reasoning.     

A reason for theoretical terms

The presence of nonobservational vocabulary is shown to be necessary for wide application of a conservative principle of theory revision.Support for this research was provided by the Office of Naval Research under contract No. N00014-87-K-0401. We thank Daniel Andler and Clark Glymour for helpful discussion.     

The effect of social support on prenatal care.

This article examines the effects of social support on the receipt of adequate prenatal care. A study was conducted to test the hypotheses that social support helps women overcome obstacles to obtaining such care, and that social support has greater effects on women facing the most obstacles. Survey data were gathered for more than 90% of the women who gave birth in Oklahoma hospitals during specific periods in the summer of 1986. The authors found only weak support for the first hypothesis, and for the second hypothesis found only support that must be qualified according to the measure of social support. Strong evidence indicates, however, that difficulty in paying for prenatal care, personal inconveniences, and unwanted pregnancies are obstacles to obtaining such care. The findings account for some of the frequently observed demographic differences associated with receipt of adequate prenatal care, although such differences persisted even after the obstacles were considered. The authors present implications for policy makers seeking to improve women's receipt of adequate prenatal care.     

AN EXPERIMENTAL COMPARISON OF THREE DIFFERENT SCHEDULES OF REINFORCEMENT OF DRUG ABSTINENCE USING CIGARETTE SMOKING AS AN EXEMPLAR

The efficacy of three different schedules of reinforcement for promoting and sustaining drug abstinence was compared in this study. Cigarette smoking was studied as an exemplar of stimulant drug self-administration. Sixty cigarette smokers were assigned to one of three groups (progressive rate of reinforcement, fixed rate of reinforcement, and yoked control). Participants in all three groups were asked to refrain from smoking for 1 week. Participants in the progressive and fixed groups achieved greater mean levels of abstinence than those in the control group. Participants in the progressive group were significantly less likely to resume smoking when they became abstinent than participants in the other groups.