Fig 1.
(a) Illustration of the experimental procedure. (b) Typical Schulte 5 × 5 table. (c) Experimental design: completion of R Schulte tables; i-th active phase of length τi followed by i-th passive phase of length ρi (waiting and preparing for the next task). (d) Layout of EEG electrodes arranged according to standard international 10–20 system.
Fig 2.
(a) Dendrogram illustrating the results of hierarchical clustering. (b) Silhouette coefficients calculated for all 22 subjects (histogram) and averaged over the subjects belonging to each of three clusters (boxes). Different clusters are marked with different colors.
Fig 3.
Three scenarios of cognitive activity during mental task processing.
(a) Relation between energies of high- and low-frequency spectral components in the left (εLH) and right (εRH) hemispheres, calculated for active (closed dots) and passive (open dots) experimental phases. The distributions are shown for three subjects belonging to different groups. (b) Coefficient ε showing the relation between energies of high-and low-frequency spectral components, calculated for each EEG channel during active (left-hand columns) and passive (right-hand columns) phases. Groups I and III contain n = 8 subjects and group II contains n = 6 subjects.
Table 1.
EEG features revealed during active phase (accomplishing Schulte table) and passive phase, in terms of coefficients εLH,RH and k.
εLH,RH is the ratio between high- and low-frequency activity in the left and right hemispheres and k = εRH/εLH is the degree of hemispheric asymmetry.
Fig 4.
Statistical measures for three scenarios of cognitive activity.
(a) Ratio ε between energies of high- and low-frequency spectral components calculated for EEG channels belonging to left (LH) and right (RH) hemispheres during active and passive phases. (b) Ratio k between values of ε calculated for left and right hemispheres during active and passive phases. Yellow bars, boxes, and whiskers indicate, respectively, medians, 25–75 percentiles, and outlines. Groups I and III contain n = 8 subjects and group II contains n = 6 subjects. *p < 0.05 via nonparametric Wilcoxon signed-rank test.
Table 2.
Schulte performance in terms of work efficiency (WE), psychological stability (PS), and warming-up work indicator (WU).
Fig 5.
Results of psycho-diagnostic tests.
Measures characterizing subject’s mental ability during accomplishing the Schulte test. (a) Average time of task completion WE (calculated via Eq 1, measured in seconds). (b) Perseverance of attention PS (calculated via Eq 3, measured in dimensionless units). (c) Average performance WU (calculated via Eq 2, measured in dimensionless units). The data are presented as mean±SD (SD being standard deviation).
Fig 6.
Sixteen Personality Factor Questionnaire.
(a) Primary factors of 16PF Questionnaire, averaged over subjects in each group (group I—dotted line, group II—solid line, group III—dash-dotted line). The dashed area highlights the factors for which significant changes between the groups are observed. (b) p-values calculated for these groups for different factors of 16PF Questionnaire via Kruskal–Wallis H test for several independent samples. The insert shows in detail low p-values calculated for A, B, C, E factors. (c-e) Values of A, B, C, E calculated for three groups (data are shown as mean±SD). Groups I and III contain n = 8 subjects and group II n = 6 subjects, *p > 0.05, **p > 0.01 via nonparamentric Mann–Whitney U test.