Two five-man teams were trained to asymptotic levels of synthetic-work performance on a multiple-task performance battery (MTPB) which required subjects to time share five individual-performance tasks and one group-performance task. Each team was then exposed four times to continuous-work and sleep-loss stresses in a repeated-measures design. Performance levels were measured in terms of 13 individual-task measures and a general mean-percentage-of-baseline measure. Individual performance decrements were found to range from 0 to 40% below prestress levels. The findings also indicated that subjects responded consistently across the four exposures to continuous work and sleep loss. Furthermore, the subjects experienced a general performance decrement across all tasks rather than a task-specific one. These findings are discussed in terms of their important implications for the design of man-machine systems and the selection of operators who are most resistant to sleep-loss stress.

The consistency and loci of leniency, halo, and range restriction effects in performance ratings were investigated in a longitudinal study. Ratings were provided by approximately 90 supervisors in a metropolitan police department, who rated approximately 350 police-rank subordinates on five occasions over a three and onehalf year period. Rating effects were computed separately as raterand ratee-based statistics, and intercorrelated among the five rating periods. T h e nature of the data set made it possible to hold either raters or ratees constant for each analysis, thus permitting inferences regarding the sources of reliable variance in effects as due to raters or ratees. It was concluded that reliable variance in mean ratings is partly attributable to ratees, but mainly introduced by raters. Reliable halo variance is attributable to raters, and range restriction is a product of stable group performance variability within intact ratee groups. Implications of these results for future rating process research are discussed.THE observation that performance rating research occupies a prominent position in the industrial psychology literature is becom-Reprint requests should be sent to Robert J. Vance,

The effects on ratings of ride quality of discomfort produced by complex vibration and noise stimuli were investigated. The initial study examined effects of simultaneous vibration in the vertical and lateral axes in a simulated passenger aircraft. The second study examined the effects of simultaneously presented vertical vibration and noise stimuli. In both studies the components of complex stimuli were found to combine their effects at low levels of stimulation but to act separately at higher levels.

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