Factors influencing mental workload indexes

Several findings of the author's own mental workload research are reviewed. Especially, factors, except task demand, influencing mental workload indexes are discussed. First, an experiment using the National Aeronautics and Space Administration Task Load Index (NASA TLX) is reviewed and the effects of a prior task load on a subsequent subjective workload are described. In a physiological measures section, the low reliability of the heart rate variability (HRV) parameters when the subjects' respiration pattern are highly irregular, and the existence of low sweat respondent, although perspiration seems to be sensitive to the workload, are indicated. Furthermore, results of the task specific physiological responses and of a HRV parameter affected by the individual characteristics, like type A behavior pattern, are shown. Discrepancy between autonomic nervous system activity measures may be solvable by introducing a new concept of autonomic space (synergism of sympathetic and parasympathetic nervous system). Finally, the need for strategies of data management concerning the individual differences is emphasized.     

Menstrual cycle effects on a VDT-based simulation task: cognitive indices and subjective ratings

It is unclear whether the menstrual cycle affects the basics of performance, mainly task performance and cognitive functions. We examined menstrual cycle effects on VDT-based task performance, cognitive indices based on the signal-detection theory, and subjective ratings in questionnaires. We experimented in three phases: premenstrual, menstrual and postmenstrual phases. Previous studies reported premenstrual tension syndrome (PMST) in the premenstrual phase. Women used physiological and psychological strategies to cope during the menstrual phase. However, task performance, cognitive indices and subjective ratings showed no menstrual cycle effects. Thus, we can conclude that the information processing for the VDT-based task was not affected by menstrual cycle.     

Relationships between subjective ratings and objective measures of performance in speechreading sentences

Ninety-six participants with normal hearing and 63 with severe-to-profound hearing impairment viewed 100 CID Sentences (Davis & Silverman, 1970) and 100 B-E Sentences (Bernstein & Eberhardt, 1986b). Objective measures included words correct, phonemes correct, and visual-phonetic distance between the stimulus and response. Subjective ratings were made on a 7-point confidence scale. Magnitude of validity coefficients ranged from .34 to .76 across materials, measures, and groups. Participants with hearing impairment had higher levels of objective performance, higher subjective ratings, and higher validity coefficients, although there were large individual differences. Regression analyses revealed that subjective ratings are predictable from stimulus length, response length, and objective performance. The ability of speechreaders to make valid performance evaluations was interpreted in terms of contemporary word recognition models.     

No pain, no gain? The importance of measuring course workload in student ratings of instruction.

Samples of about 200 undergraduate courses were investigated in each of 3 consecutive academic terms. Course survey forms assessed evaluative ratings, expected grades, and course workloads. A covariance structure model was developed in exploratory fashion for the 1st term's data, and then successfully cross-validated in each of the next 2 terms. The 2 major features of the successful model were that (a) courses that gave higher grades were better liked (a positive path from expected grades to evaluative ratings), and (b) courses that gave higher grades had lighter workloads (a negative relation between expected grades and workload). These findings support the conclusion that instructors' grading leniency influences ratings. This effect of grading leniency also importantly qualifies the standard interpretation that student ratings are relatively pure indicators of instructional quality. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Contrast and convergence effects in ratings of foods.

"A set of assumptions was made that led to the hypothesis that preference ratings for poor quality food will be lower when preceded by a good quality food than when preceded by another poor quality item (contrast effects). It was also hypothesized that preference for a good quality food will be higher when preceded by another good quality item than when preceded by a poor quality product (convergence effects). The other predictions were that preference will increase with successive presentations of the same quality item, provided no opposite quality intervenes. The predictions concerning preference for the poor quality foods were clearly confirmed, but those involving the good quality foods were not substantiated." (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Attentional processes in time perception: Effects of mental workload and event structure.

The role of attention in timing was evaluated in 2 experiments. In Experiment 1, participants reproduced the durations of melodies with either a coherent or an incoherent structure. Participants were tested under control (timing only) and detection (timing plus target detection) workload conditions. Reproductions were shorter and more inaccurate under detection conditions, and incoherent event structure extended the effect to a wider range of durations. In Experiment 2, participants reproduced the durations of auditory prose passages that represented 3 levels of mental workload and 3 levels of event structure. Both increases in workload and the degradation of structure led to inaccurate reproductions. The results point to the central role of attention in temporal experience. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Context effects on choice

Four pigeons responded on a concurrent-chains schedule in four experiments that examined whether the effectiveness of a stimulus as a conditioned reinforcer is best described by a global approach, as measured by the average interreinforcement interval, or by a local contextual approach, as measured by the onset of the stimulus preceding the conditioned reinforcer. The interreinforcement interval was manipulated by the inclusion of an intertrial interval, which increased the overall time to reinforcement but did not change the local contingencies on a given trial A global analysis predicted choice for the richer alternative to decrease with the inclusion of an intertrial interval, whereas a local analysis predicted no change in preference. Experiment 1 examined sensitivity to intertrial intervals when each was signaled by the same houselight that operated throughout the session. In Experiment 2, the intertrial interval always was signaled by the stimulus correlated with the richer terminal link. In Experiment 3, the intertrial interval was signaled by the keylights correlated with the initial links and two novel houselights. Experiment 4 provided free food pseudorandomly during the intertrial interval. In all experiments, subjects' preferences were consistent with a local analysis of choice in concurrent chains. These results are discussed in terms of delay-reduction theory, which traditionally has failed to distinguish global and local contexts.     

Caffeine self-administration and subjective effects in adolescents.

Eighteen adolescents (ages 11–15) underwent 6 independent, randomized, double-blind, placebo-controlled trials. In each trial, participants sampled a noncaffeinated and a caffeinated soda (33 mg per 8 oz) in a 2 day crossover, followed by concurrent access to the same 2 sodas the following 2 days. Four of the 18 (22%) participants met a repeatability criterion, and 1 also met a statistical criterion for reliable caffeine self-administration. Across-subjects ratings of depression, drowsiness, and fatigue were increased on noncaffeinated compared with caffeinated soda sampling days. These results are similar to, but less robust than, previous research in adults showing that 31–36% of coffee drinkers reliably self-administer caffeine and experience adverse effects from caffeine abstinence. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Context effects in social perception.

"Concerned with the problem of field determinants of social perception, this study investigated contextual effects on judgments of photographs of persons. Photographs, designated as targets, were presented in contexts of two other photographs which were expected, on the basis of previous research, to vary in their probability of eliciting a particular judgment along a specified bipolar trait dimension. Data obtained clearly supported the hypothesized inverse relationships between the probability of the context eliciting a particular judgment and that of the target eliciting a similar judgment." (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

A meta-analysis of ratee race effects in performance ratings.

Conducted a meta-analysis of how the race of the ratee affects performance ratings by examining 74 studies with a total sample of 17,159 ratees for White raters and 14 studies with 2,428 ratees for Black raters. The 5 moderators examined were the study setting, rater training, type of rating, rating purpose, and the racial composition of the work group. Results show that the corrected mean correlations between ratee race and ratings for White and Black raters were .183 and –.220, with 95% confidence intervals that excluded zero for both rater groups. Substantial moderating effects were found for study setting and for the saliency of Blacks in the sample. Race effects were more likely in field settings when Blacks composed a small percentage of the work force. Both Black and White raters gave significantly higher ratings to members of their own race. It is suggested that future research should focus on understanding the process underlying race effects. References for the studies included are appended. (47 ref) (PsycINFO Database Record (c) 2011 APA, all rights reserved)     

Looking back and looking ahead: Adult age differences in consistency of diachronous ratings of subjective well-being.

The goal of this study is to investigate the consistency of diachronous ratings of subjective well-being (SWB). A heterogeneous sample (25-74-year-olds; N=3,596) provided ratings of their present SWB, reconstructed their SWB of 10 years ago, and anticipated their SWB 10 years from now. Developmental tasks and self-evaluative principles were used to predict age differences in diachronous consistency. As predicted, in young adulthood, past SWB was rated lower and future SWB higher than present SWB. In contrast, in later adulthood, the past was rated higher and the future lower than present SWB. Analyses of rank-order consistency demonstrated that in later adulthood both future and past SWB were more strongly related to present SWB than in young adulthood. Results show how models of self-evaluation play out at different points in the life span. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Physiological and subjective measures of workload when shovelling with a conventional and two-handled ('levered') shovel

Previous studies have suggested that the two-handled (levered) shovel is advantageous over the conventional spade from a biomechanical point of view. The aim of this experiment was to determine whether less energy was consumed while shovelling a load of sand with this shovel compared to a conventional tool. Accordingly, an experiment was designed in which subjects (n = 10) shovelled 1815 kg sand under laboratory conditions using either a conventional or a levered shovel. Heart rate and oxygen consumption were measured continuously during the trial and subjective data on perceived exertion, general fatigue and body discomfort were recorded after the trial. Although total energy expenditure was similar under both conditions (120 +/- 20 and 125 +/- 25 kcal; conventional versus two-handled spade), average heart rate was 4% higher when the two-handled shovel was used (p < 0.05). In addition, the mass of sand per scoop was 4% less with the two-handled shovel (p < 0.05). In conclusion, subjects used similar energy expenditure to shovel 1815 kg sand with the conventional shovel and the two-handled tool despite lower mass of sand per scoop with the latter. This can be explained by the fact that the increased mass of the additional handle compensated for the lower mass of sand per scoop. The higher average heart rate while shovelling with the two-handled shovel can be explained by the more erect posture.     

Context effects in judgments of causation.

It is hypothesized that causal explanations for an occurrence vary as a function of the causal background against which the occurrence is considered. Three experiments are presented that test propositions regarding the operation of the causal background in the selection of causal explanations. Findings indicate that factors previously shown to affect subjects' attributions—specifically, role (actor vs. observer), covariation information (consensus and distinctiveness), and quality of performance (positive vs. negative)—may do so by guiding subjects' selection of a causal background. Evidence indicates that these factors may not have the predicted effect on subjects' attributions when competing cues, such as context or wording of the causal question, suggest the relevance of conflicting causal backgrounds. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Relations between infant behavior ratings and concurrent and subsequent mental test scores.

125 Mexican-American infants of lower socioeconomic status were administered the Bayley Scales of Infant Development at 12 and 24 mo of age; 66 of these Ss were later given the Stanford-Binet Intelligence Scale at 36 mo of age. Results indicate that when behavioral clusters are derived in the fashion used by A. Metheny et al (1974), similar findings emerge from the correlational analyses with the exception of a somewhat higher prediction from Extraversion scores in the present report. When behavioral factors were derived by a principal-components analysis, however, it was found that 5 factors that differed substantially in structure from the composites proposed by Matheny et al emerged from the analysis. Multiple regression analyses revealed that neither the factor scores from the principal components nor the composite scores for Primary Cognition and Extraversion added significantly to the prediction of subsequent Mental Performance beyond what was afforded by 12-mo Bayley Mental Development Index scores. (21 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Context effects in left-right shape discrimination.

The difficulty of discriminating between left–right orientations of a shape has usually been attributed to symmetrical coding in the brain or to the nature of perceptual learning. However, recent work on the context-dependent nature of the difficulty challenges such explanations and supports a more cognitive approach to the problem. The present work examined the basis for left–right difficulty in the standard two-choice task (stimuli aligned side by side) in children of 3 to 4 years. Experiment 1 found that children who learned the task with the easy, single-stimulus procedure could generalize to the difficult, two-choice task. Subsequent experiments found that the difficulty in learning the two-choice task could not be attributed to the attentional demands of the two stimuli, nor to the use of the second stimulus as a spatial referent for defining orientation. The data suggested that the standard two-choice task is difficult because it promotes the use of two competing orientation judgments. We conclude that the difficulty of left–right judgments lies in the cognitive demands of the task and is to be understood in the same terms as other problems in cognitive development. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Stimulus dimensionality effects in mental rotation

Do 3-dimensional (3-D) figures require more time to rotate mentally than do 2-dimensional (2-D) figures? This question was examined in 2 experiments incorporating 15 2-D and 15 3-D stimuli. For 3-D stimuli, block figures were used of the type used by R. N. Shepard and J. Metzler in their classic studies. For 2-D stimuli, block figures were also used, but with all cubes in a single plane, resulting in 2-D and 3-D figures matched on surface features. Three-D figures elicited steeper slopes than did 2-D figures, supporting the view that the mental rotation of visual representations is sensitive to stimulus dimensionality. The authors summarize the results of several mental rotation studies that investigated stimulus dimensionality and suggest that the evidence across studies is consistent with the present finding. They discuss 2 plausible loci for the dimensionality effect in S. M. Kosslyn's (1980) theory of mental imagery.     

Cardiovascular and subjective effects of intravenous cocaine administration in humans

Nine volunteer subjects were tested with intravenously administered cocaine hydrochloride in doses ranging from 4 to 32 mg, as well as 10 mg of dextroamphetamine sulfate. Measures of cardiovascular and subjective effects were made. Generally parallel dose-effect functions were obtained for heart rate, blood pressure, Addiction Research Center Inventory scores, Profile of Mood Scales, and subject ratings. A substantial effect on each of these variables was recorded after 8 mg of cocaine. The increase continued and peaked at approximately 16 mg after which it usually leveled off. Ten milligrams of dextroamphetamine generally had an effect comparable to 8 to 16 mg of cocaine.     

Examination of race and sex effects on performance ratings.

The effects of rater source, rater and ratee race, rater and ratee sex, and job type were investigated on ratings collected for 8,642 first-term Army enlisted personnel. Ratings were made on 10 behaviorally based dimensions developed for evaluating all first-term soldiers. Results of between-Ss analyses similar to those conducted in past research revealed significant main effects and interactions for sex, race, rater source, and job type, but the variance accounted for by these effects was minimal. Repeated measures analyses were also performed, with each ratee evaluated by one Black and one White rater for the race effects analyses and one female and one male rater for the sex effects analyses. These analyses, which unconfounded rater bias and actual performance differences, yielded results similar to those obtained with the between-Ss design. Implications of the findings are discussed. ? (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Second-order effects in mental health treatment.

Argues that mental health clients are typically processed through a fairly standardized, complex professional system which, in its pursuit of salutary "helping" goals may also be occasioning serious, negative 2nd-order effects for its clients. Clinicians have paid little attention to this possibility, and negative 2nd-order effects are thus not typically monitored in therapy or studied in research. A model for identifying and evaluating treatment effects is proposed. The important professional implications of treatment-contingent negative 2nd-order effects are discussed. (35 ref.) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Clinical outcome, consumer satisfaction, and ad hoc ratings of improvement in children's mental health.

Mental health clinics and managed care organizations assess treatment effectiveness with consumer satisfaction measures and ad hoc measures of improvement obtained from a single informant; some of these measures are as simple as asking clients whether they improved during treatment. In the present correlational study of 199 treated adolescents, we used a multitrait-multimethod analysis to examine psychometrically measured pathology change (pre- and postassessment of symptoms and functioning), consumer satisfaction, and perceived improvement reported by multiple informants. Confirmatory factor-analytic results indicate that (a) outcome variance due to multiple informants cannot be ignored, (b) consumer satisfaction is unrelated to pathology change, and (c) parent-reported perceived improvement ratings are more akin to satisfaction than to pathology change. (PsycINFO Database Record (c) 2010 APA, all rights reserved)