Objectives. To assess the objectivity of measurements of the level of drowsiness in subjects using a previously developed monotonous psychomotor bimanual tapping test performed on mobile devices running Android OS. Materials and methods. A total of 494 1-h experiments were run in 102 students using a psychomotor test. Correlations between sleepiness levels on the Karolinska Sleepiness Scale (KSS) and the Epworth Sleepiness Scale (ESS) and behavioral test scores were assessed using linear mixed models. Results. Statistically significant relationships were demonstrated between increases in KSS scores and indicators such as decreases in the total number of button presses and increases in the frequency of microsleep episodes. There were no statistically significant relationships between ESS scores and performance on behavioral tests. Conclusions. studies using a large statistical dataset showed significant correlations between psychomotor test parameters and the level of drowsiness on the KSS, which supports the validity of a mobile app which has been developed to determine ongoing drowsiness/vigilance levels in the field.