David G. Humphrey

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The authors examined the question of whether a decrease in the efficiency of inhibitory processing with aging is a general phenomenon. Thirty elderly and 32 young adults performed a series of tasks from which the authors could extract measures of inhibitory function. The tasks and task components included response compatibility, negative priming, stopping,(More)
A study was performed to examine the utility of an ERP-based irrelevant probe technique for the assessment of variations in mental workload. Ten highly trained Navy radar operators performed a simulated radar-monitoring task which varied in the density and type of targets to be detected and identified. This task was performed in the presence of a series of(More)
The authors examined the ability of younger and older adults to search for targets defined by single features (feature search), conjunctions of 2 features (conjunction search), and conjunctions of 3 features (triple-conjunction search). Feature search was relatively age-invariant, with both older and younger adults displaying shallow search slopes. However,(More)
We develop a variant of the Nelder-Mead (NM) simplex search procedure for stochastic simulation optimization that is designed to avoid many of the weaknesses encumbering similar direct-search methods—in particular, excessive sensitivity to starting values, premature termination at a local optimum, lack of robustness against noisy responses, and(More)
The main goal of the present study was to examine the feasibility of employing event-related brain potentials to measure dynamic changes in mental workload. Subjects performed two tasks, monitoring and mental arithmetic, both separately and together. Following an analysis of the performance, subjective workload ratings, and average ERP data in the single-(More)
We investigated the influence of extended wakefulness on automatic and nonautomatic processes in memory and visual search tasks. Subjects were trained in consistently mapped and variably mapped versions of each task, attaining automatic performance in the consistently mapped versions. We then recorded performance measures and event-related brain potentials(More)
Due to the fact that studies are often performed with the use of computer simulation but little or no effort is made to optimise the results, this work was undertaken in an attempt to find an automated method of optimizing simulation input parameters in order to improve overall performance of the corn-processing facility being studied. The Pillsbury Company(More)
The electrochemical oxidation of cis,mer-[Mn(CO)(2)(eta(1)-dpm)(eta(2)-dpm)Br] (dpm = Ph(2)PCH(2)PPh(2)), or (cis,mer)(0),()()has been examined in dichloromethane (0.1 M Bu(4)NPF(6)) by voltammetric, bulk electrolytic, in situ and ex situ spectroelectrochemical and simulation techniques. On the voltammetric time scale at 20 degrees C, the neutral(More)
The present research examined age-related differences in the use of structural aspects of the visual environment to facilitate the processing of task-relevant stimuli. More specifically, our study considered age-related differences in the use of color and proximity to facilitate the recall of alphabetic strings. The dependent measure of interest was the(More)