Social psychophysiological compliance in a four-person research team.

A continuous, non-invasive and objective measure of teamwork effectiveness could be very useful to the human factors design community. Social psychophysiological compliance (SPC), estimated by scoring the extent that heart rate variation was synchronous across team members, was explored as a predictor of teamwork effectiveness during 20 real planning meetings over a 6-month period. Speech activity and heart rate variability of all four (2 male, 2 female) team members were continuously monitored. Exploratory analyses tested if team member ratings of various aspects of teamwork effectiveness were predicted by SPC scored (1) over whole meetings, (2) during one team member's speech, (3) during periods in which two team members spoke in sequence or (4) over 30-s periods and averaging highest values. SPC during periods of sequential speech negatively predicted team members' ratings of Team productivity, Quality of communication, and Ability to work together. SPC shows potential as an objective, non-invasive means to monitor teamwork effectiveness but this relationship warrants further investigation and replication before use in ergonomics applications.

Social-physiological compliance as a determinant of team performance.

A cybernetic model of behavior predicts that team performance may depend on physiological compliance among participants. This laboratory study tested if compliance in electrodermal activity (EDA), heart rate or breathing in two-person teams (N=16) was predictive of team performance or coordination in a continuous tracking task simulating teleoperation. Visual contact among participants was manipulated. Physiological compliance was scored with weighted coherence and cross correlation. Separate multiple regression analyses revealed that the task completion time was predicted by coherence measures for EDA and heart, but only at a trend level for breathing. Task completion time was also predicted by heart cross correlation. Team tracking error was predicted by coherence measures for EDA, heart and breathing, and also heart cross correlation. While social-visual contact did not have an impact, physiological compliance was predictive of improved performance, with coherence robust over all three physiological measures. Heart cross correlation showed the strongest predictive relationships. These results provide evidence that physiological compliance among team members may benefit team performance. While further study is needed, physiological compliance may someday provide a needed tool for the study of team work, and an objective means to guide the ergonomic design of complex sociotechnical systems requiring a high degree of team proficiency.

Frequent short rest breaks from computer work: effects on productivity and well-being at two field sites.

Computer operators at two work sites (n = 73, n = 19) were prompted to take three 30-s and one 3-min break from computer work each hour in addition to conventional rest breaks. Some operators were asked to perform stretching exercises during the short breaks. Mood state and musculoskeletal discomfort were assessed at each work site over a 2- or 3-week baseline period and a 4- or 6-week treatment period, respectively. Operator productivity measures were obtained from company records. Operators complied with about half of the added breaks but favoured 3-min breaks over 30-s breaks. No improvement in productivity or well-being was found at the larger work site. At the smaller work site, productivity, eye, leg and foot comfort all improved when the short breaks included stretching exercises. These results provide evidence that frequent short breaks from continuous computer-mediated work can benefit worker productivity and well-being when the breaks integrate with task demands.

Work-physiological synchronization as a determinant of performance in repetitive computer work.

The present study tested the hypothesis that performance would improve when the work rhythm of a highly repetitive task was synchronous with a worker's internal physiological rhythms. Experienced office workers (n = 20) used video display terminals (VDTs) to perform a repetitive, self-paced data-entry task in a simulated office environment over a 2-day period. Each work day consisted of six 40-min work periods. Work rhythm changes were induced by varying input data field lengths (3-13 characters) across eleven of the twelve work periods. The degree of synchronization between the work and breathing rhythms, and also between the work rhythm and variations in the interbeat interval, was scored using cross-spectral analysis. Synchronization scores were then used to predict keying performance using multiple regression analysis. The degree of synchronization between the work and breathing rhythms was not predictive of performance. However, increased synchronization between the work and cardiac rhythms was predictive of (a) increased keystroke output, (b) lower error rate and (c) lower correction rate. The results suggest that performance in repetitive VDT work might improve if the task is designed to promote work-physiological synchronization.

Finger tremor after carbon disulfide-based pesticide exposures.

Index finger tremor accompanying voluntary movement was studied in 19 age-matched control subjects and in 19 grain industry employees chronically exposed to carbon disulfide-based fumigants. Visual judgments of tremor amplitude made by neurologists during clinical examinations equaled the sensitivity of computerized tremor amplitude measurements. Tremor frequency variations detectable only with computerized measurement were present in grain workers with and without increased tremor amplitudes. Frequency differences discriminated between normal subjects and 74% of the grain workers. The distribution of tremor frequency power in the grain workers was often sequestered at 5 to 7 Hz, reminiscent of tremor in idiopathic Parkinson's disease. These findings suggest that the measurement of subtle tremor frequency changes may provide an early indication of chronic carbon disulfide poisoning.

Differences in frequency of finger tremor in otherwise asymptomatic mercury workers.

Tremor was measured from the index finger during low force, position holding in 18 control subjects and 18 battery workers with low level exposure to mercury. All workers were asymptomatic on clinical neurological examination. No differences were found in average tremor amplitudes between the groups, but statistically significant abnormalities in tremor frequency distribution existed. Tremor power spectra in the group of mercury workers were shifted toward the higher frequencies and compressed into narrow frequency peaks. These results suggest that measurements of finger tremor that evaluate the frequency distribution can produce a higher diagnostic yield than traditional visual clinical judgement. The findings also confirm other reports that currently permitted exposures to mercury are associated with subtle but distinctive differences in tremor accompanying voluntary movement.

Behavioral effects of increased CO2 load in divers.

The behavioral effects of elevated PACO2 were examined to clarify risks due to CO2 retention in diving. In two separate laboratory studies, experienced divers breathed 6% CO2 mixtures under normobaric conditions. Normoxic study: Subjects (n = 8) first breathed air (control); then 6% CO2, 21% O2, balance N2 (exposure); and then air again (postexposure). Hyperoxic study: Subjects (n = 10) first breathed 100% O2; then 6% CO2 in O2; and then O2 again. Subjects performed a test battery in each condition. In the control and postexposure conditions, tests consisted of simple and choice reaction time, postural sway, tremor, and hand steadiness. In the exposure conditions, only the simple and choice reaction time tests were performed. No significant performance decrements during CO2 exposure were found in either study. However, regression analyses indicated that changes in postural sway, tremor, and decision-making time after normoxic CO2 exposure were proportional to decrements in individual end-tidal PCO2 levels following CO2 exposure. We conclude that divers may be at risk for performance impairment immediately after a period of CO2 retention.

Microbreak length, performance, and stress in a data entry task.

The effects of brief rest pauses on performance and well-being were evaluated for a highly repetitive, data entry task. Experienced data entry operators (N = 20) performed the task in a two-day experiment in a simulated office environment. Each day was divided into six, 40-min work periods. Subjects took a brief rest pause at the workstation (microbreak) in the middle of each work period. Subjects were instructed to terminate this microbreak when ready to resume work. Keystroke rate, error rate, correction rate, heart rate and heart rate variability were scored for each half of the work period. In addition, mood states before and during the work period were assessed. Microbreaks were found to average 27.4 s in duration. High ratings of fatigue and boredom during the work period were associated with longer microbreaks, suggesting that the break period was self-adjusted relative to mood state. In addition, correction rate and heart rate were lower following long microbreaks, implying that the degree of recovery was linked to the length of the microbreak. Comparison of keystroke output and correction rate before and after the microbreak, however, revealed that performance worsened after the microbreak, suggesting that subjects terminated microbreaks before complete recovery could occur.