Effects of Alcohol on Visual, Cognitive & Motor Performances Related to a Complex Manual Control Task

Transcription

1 Effects of Alcohol on Visual, Cognitive & Motor Performances Related to a Complex Manual Control Task R obert S. K ennedy*, Janet J. Turnage*, D eborah L. H arm ** and Julie M. Drexler*** *Essex Corporation, Orlando, FL **N A SA Johnson Space Center, Houston, TX ***Essex Corporation, Orlando, FL. A B ST R A C T U sing alcohol as a challenge, w e evaluated the sensitivity of behavioral tests from four perform ance dom ains (Visual Tem poral Factors, Cognitive Perform ance, Psychom otor Tracking, Visual Spatial Acuity). T he tests, predictive o f a w ide range o f hum an abilities, w ere also predictive o f a com plex m anual control task (a sim ulated Shuttle Landing task). O ur expectation w as that the m ore basic m easures (e.g., spatial and tem poral visual acuity, tracking) w ould show less disruption as a function o f the alcohol challenge than the m ore com plex tasks (reasoning, pattern com parison, spatial perception). W e tested 28 subjects on: five tests of visual acuity; six tests o f visual tem poral acuity; five cognitive tests; and tw o tracking tasks. Subjects w ere then dosed to a blood alcohol concentration (BAC) above 0.10 and w e repeated the four battery testing regim e four additional tim es as we m easured BA C 's of the (descending) alcohol rem oval curve with an Alcosensor IV. Based on the correlations o f these tests with the sim ulated Shuttle Landing task, norm alized com posite scores were developed for each o f the four perform ance dom ains. U sing these surrogate scores, w e found a substantial, consistent, and significant sensitivity o f each o f the com posites to alcohol and som e differential effects w ere noted am ong the com posites. Visual Acuity, the m ost "basic" ability represented, show ed m inim al practice effects over pre-trials and there w ere m inim al alcohol induced effects. How ever, the Tem poral Factors com posite (visual processing abilities) considered as m ore basic than the cognitive abilities, show ed an equivalent decrem ent and increased sensitivity at lower dosages. The Tracking com posite (sim ple m otor skills), typically w as m ore resistant to dism ption than cognitive abilities and show ed a m odest decrem ent and relatively rapid recovery o f perform ance as expected. In a follow on study, the Shuttle simulation task which is an operationally meaningful task, but with high reliability, was

2 show n to be at least as sensitive to the same alcohol dosages as the cognitive and tem poral factors tests. IN TRO D U C T IO N In previous w ork w e developed and reported on batteries o f com puterized tests o f four perform ance dom ains (contrast sensitivity, cognition, psychom otor skills and tem poral aspects of vision) (Turnage, Kennedy, Smith, Baltzley, & Lane, 1992; Jones & Kennedy, 1995). Norm s, reliabilities, factor structure and predictive validities are available with these tests. A s others have found differences in sensitivity with different tests, w e wondered w hether these tests o f different aspects o f the perception-action cycle would be differentially sensitive to alcohol dosages and decided to run all tests in the sam e experiment. Also because w e had access to a version of NASA 's sim ulated Shuttle Landing (C.R. Justiz, personal com m unication, M arch, 1993), we elected to determ ine w hether these tests alone and in com bination w ould be predictive o f this com plex skill. First it was necessary to evaluate the Shuttle Landing Task for metric properties. Then we determ ined the correlation of the tests of all four batteries to the Shuttle (Experim ent 1). From these relations, predictive equations were obtained for each battery against the Shuttle Landing perform ance scores that were obtained after that task had been practiced extensively. These predictor or surrogate (Kennedy, Turnage, & Lane, 1997) scores were then exam ined by alcohol challenge (Experim ent 2). Then the com plex task itself (Shuttle Landing) was exam ined under graded dosages o f alcohol (Experim ent 3). O ur hypotheses w ere that while several o f the tests in these batteries would be predictive of shuttle perform ance, they would show differential sensitivity to the alcohol dosages. Experim ent 1 W e tested 31 subjects on: 1) two measures o f contrast sensitivity - a com puter based battery and an industry standard (Vistech 6500); 2) seven tests o f visual temporal acuity (flicker, phi, m eta contrast, etc. [see Jones & Kennedy, 1995 for a complete description]); 3) nine cognitive tests in the D E LTA (form erly A PTS) battery (grammatical reasoning, pattern com parison, code substitution, etc.); and 4) three video gam es (tracking, aiming, etc.). These tests w ere practiced over a total of seven sessions, lasting about one hour each. In addition, perform ance on the newly developed Portable Inflight Landing Operations Trainer (PILOT) was scored for 56 Shuttle

3 landing approaches. The PILO T Task, as used by N A SA for astronaut training, is designed to land the shuttle from a preset position, guiding it with a joystick control, to a "dead-stick" landing. The task requires both m otor and cognitive (strategy) skills to complete. Reliability turned out to be high w ith estim ated values for m eans o f 12 trials o f r>.95. Using the stabilized scores o f the PILO T task (i.e., scores after the 24th approach/landing) as a criterion, correlations w ere run for all the perform ance tests. Therefore, the tests from each o f the four batteries w ere correlated with the criterion task perform ance (i.e. Shuttle landing), and w ere also found to be som ew hat correlated with each other. The correlations o f tests w ithin a dom ain (e.g., the visual acuity tests, the cognitive tests, etc.) w ere higher than correlations o f tests betw een domains. A m ultiple regression equation applied to the data show ed m ultiple r's for each battery against the Shuttle Landing task to range from, Assum ing that the test batteries could be ordered hierarchically for com plexity (e.g., visual acuity, m otor skill, tem poral acuity, cognition), w e used this hierarchy as a m odel for entry into a m ultiple regression equation. The analysis revealed the following: after visual and m otor tests w ere added, m ost o f the variance w as predictable, however, there w as some unique residual perform ance predictable from the m ental tests. Based on this relationship to the Shuttle Landing score, variance weighted com posites w ere also com puted. For early, m iddle and late practice, the scores were converted to standard scores, and then averaged, w ith variables given the sign o f their correlations w ith the Shuttle Landing. Thus, correlations o f the com posites with other variables will be com parable in sign to the correlation of those variables w ith Shuttle. The com posite intercorrelations show ed the sam e trends identified above. Experim ent 2 Subjects. Twenty-eight students (16 m en and 12 wom en; m ean age = 30.6 years) attending Casper College or the University o f W yom ing volunteered as subjects. The typical subject described him or herself on the Iow a Scale o f Preoccupation w ith Alcohol (M ulford & M iller, 1961) as having m oderate previous experience with alcohol, no past history of chronic dependency o f any type, good general health, and low risk for future problems with alcohol

4 Apparatus. T he study battery consisted o f the Contrast Sensitivity plates; six tem poral factors tasks (Saccadic Accuracy, form erly called DVA; Simultaneity; Apparent M ovem ent; Bistable Stroboscopic M otion; Critical Flicker Frequency; and Backw ard M asking); five tests from the D E LTA battery (Gram m atical Reasoning, Code Substitution, Pattern Com parison, M anikin, N on-preferred Tapping); and two videogames (Air Com bat Maneuvering, Down Hill Skiing). B lood alcohol concentrations (BAC) were m easured in m g/m l, using the Intoxim eter A lcosensor IV breath analyzer. Subjects were dosed to.11+ BAC and subsequently follow ed on the descending limb of the alcohol removal curve. C om pared to the six pre-alcohol trial scores, Figure 1 shows the relative loss in perform ance on the four test batteries. It may be seen that contrast sensitivity profits least by practice and the alcohol induced loss is also least. Tem poral factors after session one show s m inim al practice effects and large alcohol induced losses. Both cognitive and psychom otor tasks show ed large practice effects, but cognitive losses due to alcohol were m ore pronounced w ith cognitive than with the psychom otor tasks. Consistency of Patterns. Figure 1 places all the surrogate variables on a com m on axis expressed in standard score units. W hile the degree o f decrem ent varies am ong com posites, the consistency o f patterns is striking. It is im portant to recognize that the various com posites represent a considerable range o f abilities, separated by a considerable distance along the hierarchical continuum. This is not all that surprising. Positive abilities tend to be positively correlated, and will thus show sim ilar patterns. The consistency o f patterns, however, indicates an encouraging reliability o f m easurem ent across the hierarchical ability continuum, that is, the tests are working as intended

5 Figure 1. All surrogates by alcohol level Surrogate Standard Scoras Saquanca 1-6 Is Practlca (.00 BAC); Saquanca 7-12 Is BAC Laval Experim ent 3: Figure 2 show s alcohol dosage and PILO T perform ance as a proportion o f baseline where B A C =.00. It is clear that perform ance reduction for this com plex high fidelity sim ulation task is proportional to alcohol dosage and the proportion of the decrem ent resem bles the changes obtained with Tem poral Factors tests and with the Delta cognitive tests. Figure 2. Sim ulated Shuttle Perform ance vs. Alcohol Dosage 5 0 i Bm <IIin Blood Alcohol Content

6 DISCUSSION The principal objective of this study was to evaluate com puterized test battery perform ance of different types for their sensitivities to alcohol. To this end, we obtained m ultiple prediction equations for each of the test batteries to a high fidelity and operationally m eaningful task. A secondary objective was to determ ine if the different classes of tests, tapping a w ide range o f hum an abilities, show ed differential patterns of decrem ent under alcohol. There is indeed a substantial, consistent, and significant sensitivity o f each of the norm alized com posite scores for the four batteries to alcohol. The dosage effects (BAC levels) likewise show consistent patterns across all surrogates, i.e., performance decrement is at least monotonically related to BAC level. There were also som e differential effects. Based on relevant findings in a previous shuttle sim ulator study, we expected those measures, which were m ore basic on a hierarchical continuum o f perform ance com plexity, to show: a) smaller practice effects; and b) less disruption as a function of alcohol challenges. These expectations were in part confirm ed. Contrast Sensitivity, the m ost "basic" o f the abilities represented, shows both m inim al practice effects and m aterially sm aller alcohol effects. It is of interest, however, that the Tem poral Factors surrogate, representing visual processing abilities that we normally consider as m ore basic than the cognitive abilities tapped by the D E LTA surrogate, which shows an equivalent decrem ent, and the Tem poral battery retains better sensitivity at lower dosages. This form o f visual processing m ay be m ore com plex physiologically or m ore sensitive to alcohol than was previously envisioned. In this study, the psychom otor surrogate contains only Tracking and ACM, both o f w hich are largely sim ple m otor skills in content. W ell practiced m otor skills are typically m ore resistant to dism ption than cognitive abilities, and the modest decrem ent and relatively rapid recovery o f perform ance on the psychom otor surrogate was as expected. In sum, the surrogates tended to: a) be highly related to shuttle landing sim ulator performance; b) be sensitive to alcohol stress and highly reliable; and c) represent sufficiently different aspects o f human abilities to be exam ined separately in future studies examining response of shuttle-landing related performance to other stressor variables. In the third study, the Shuttle task itself was tested under alcohol challenge. This test, while a high fidelity, com plex task, is also a task with exceptionally high retest reliability (Harm, Justiz, Kennedy, Lane, & Sandoz, 1996). W e found that the task was particularly sensitive to low er dosages of alcohol show ing a nearly 20% loss at 0.04 BAC and above

7 REFERENCES Harm, D. L., Justiz, C. R., Kennedy, R. S., Lane, N. E., & Sandoz, G. R. (1996). Metric properties o f a simulated shuttle lauding task: Applications fo r ground-based experiments. Presented at the 2nd NA SA /AIAA Life Sciences & Space M edicine Conference, Houston, TX. Jones, M. B., & Kennedy, R. S. (1995). Tem poral factors in visual perception: A differential approach. Perceptual and Motor Skills, 81, Kennedy, R. S., Tum age, J. J., & Lane, N. E. (1997). Developm ent o f surrogate m ethodologies for operational perform ance measurement: Empirical studies. Human Performance (In press). M ulford, H. A., & M iller, D. E. (1961). An index o f alcoholic drinking behavior related to the meanings of alcohol. Journal o f Health and Human Behavior, 2, T um age, J. J., Kennedy, R. S., Smith, M. G., Baltzley, D. R., & Lane, N. E. (1992). D evelopm ent of microcom puter-based mental acuity tests. Ergonomics, 35(10),