The following indices of psychophysiological characte-ristics of operators have been obtained as a result ofthe investigations, which characterize CNS functioningbefore and after shift work (Table 2).implemented with the use of protective non-transparenteye-glasses with built-in colored LEDs in order to providewith standard proposal of irritants and a proper contrastof the background and stimulus. The following psycho-physiological characteristics of the visual analyzerfunctioning were determined (Table 1):The diagnosis of the functional (FMNP) was madeaccording to the modified M.V. Makarenko’s method [19]with a feedback. The shortest exposure, using 200conditioned visual irritants: red, green (exciting irritants)and blue (breaking irritant) of colors, in which a respondentdifferentiated these signals correctly, was FMNP index. Inaddition, the total time and effectiveness of a taskexecution were taken into account.The effectiveness of the task execution (Е) was calculatedby the formula, developed for the assessment of the degreeof the information value relatively to equiprobableresponses [20].where р is a probability of an erroneous actionAs a result of the analysis of distribution of psychophysio-logical characteristics the availability of their significantdeviation from the normal law has been established,pointing to a definite heterogeneity of the group andthe presence of individuals with different disorders amongrespondents before and after 24-hour shift work. So, itwas important to distinguish homogenous subgroups forthe further stage of investigation. For this purpose a clusteranalysis was taken (a correlation coefficient betweenthe rated differences of psychophysiological indicesFMNP, SNP & Ind before and after work was taken asa criteria for clustering). As a result, two subgroups, similarby their psychophysiological parameters with differentmanifestations of shifts in work capacity, have been chosen.The first related to 57% respondents. The statisticalindices have been calculated separately for the first andthe second subgroups before and after work (B 1 – beforework, А 1 – after work for the first group, and B 2 and А 2 – forthe second, respectively).The lability of nervous processes was determined byindices of the critical fusion frequency of red (CFFr) andgreen (CFFg) colors. The maximum frequency, at whicha respondent records a moment of disappearance orappearance of light flickers, is considered to be the levelof manifestation of this property [21]. It is considered thata higher is the frequency of irritation in these of thosenervous structures in responses, the higher is lability ofnervous processes, expressed in Hz. In order to determinethe degree of fatigue by CFF parameters, an index of colorasymmetry was calculated (Ind) [22] by the formula:For assessing other indices the results of testing of eachrespondent are described with the function, whichadequately (significance p

If we consider the dynamics of changes in the signal the definite level of work reliability, are presented belowexposure in the test in the feedback regime (in the case of ( T a ble 3).a correct reaction to an irritant its exposure decreases, and Here we can clearly see the identity of initial exposurein the case of an erroneous one - increases) we can note level characteristics of both subgroups. On the otherone interesting peculiarity. In long-term exposures of hand, the resulting levels of the mentioned subgroupsthe assigned signal the number of erroneous actions is differ significantly, beginning with 50% work reliability,minimal, whereas in а boundary short-term exposures – it confirming our conclusions on the difference ofcan reach 100%. Intermediate values of exposure duration mechanisms of fatigue development in the subgroupscause the increase of the number of errors. The regularity concerned.of changes in the dependence of an error occurrence onthe exposure duration for each respondent is very indiviindicesof the intensity before and after work is likely toThe availability of the significant difference betweendual, however, the type of such regularity can be describedwith a definite precision, using a logistic curve. Thus, for be a very significant result in solving the task ofeach individual it is possible to calculate coefficients of distinguishing operators with high level of reliability. If forthe function:, which adequately (with the first subgroup such significant differences are definedhigh level of significance р