Approximate number sense is the ability to evaluate quantitative information without using symbols. The system of nonsymbolic numerosity representation is associated with the evaluation of non-numerical visual characteristics; with the congruency effect reflects this relationship. The congruency effect is considered as the difference in accuracy between congruent items in which non-numerical visual parameters positively correlate with quantitative ones, and non-congruent tasks in non-symbolic comparison tests. The article discusses two main theories explaining the process of nonsymbolic numerosity representation, in particular, the theory of the "number sense" and the sensory integration theory. Each of these theories suggests different explanatory models of the congruency effect, such as the inhibition model and the Attentional bias induced by stimulus control (ABC) model. In the experimental study, it was investigated to what extent the changes of the congruency effect depend on the format of the presentation of stimuli and the duration of stimuli presentation. In a sample of 97 students, a nonsymbolic comparison test was used in two formats, mixed (when the compared sets of objects are not spatially separated from each other) and separated. Each person performed nonsymbolic numerosity comparison tasks under conditions of short time presentation of stimuli (400 ms) and long time presentation of stimuli (1000 ms). For analysis of results generalized linear mixed effects models were applied. The results indicate that the congruency effect decreases under conditions of longer presentation of stimuli, however, this change is found only in the separated format of presentation of stimuli. In a mixed presentation format, when the assessment of visual parameters becomes less confident, there is no congruence effect. With an increase in the duration of presentation of stimuli, it becomes the opposite, i.e. the accuracy of nonsymbolic comparison in incongruent tasks has become higher than in congruent ones. Generally speaking, the results are in line with the "number sense" theory and have been elaborated upon. In general, the nonsymbolic numerosity representation considered as the adaptive and fluent interaction of two processes - the direct evaluation of numerosity and the evaluation of non-numerical visual cues. © 2024 Tomsk State University. All rights reserved.