## Materials and Methods
### Procedure  
Participants were seated in an adjustable chair in front of an office table with the monitor. To ensure head position stabilization, a chin rest was used. The experiment consisted of six blocks. Each block contained three conditions (M, N, T). The order of conditions was randomly counterbalanced in the group, but was the same over blocks for a single participant (e.g., MNT, MTN, TNM, etc.). Before the start of the first block, the experimenter showed to a participant the visual display of the task (with moving balls) and in detail explained what the participant should do. During training, the position of the microphone was also adjusted so that it could pick up the voice confirmations, while not distorted from breathing artifacts. The first block was considered as practice, and the participants were allowed to ask any questions during the runs. The data from the subsequent five blocks were used for analysis. Before each block, the eye tracker was calibrated using its native 7-points calibration procedure. If the experimenter noticed that the participant experienced problems with selection or the participant themselves reported such problems, the eye tracker was recalibrated, and the run was overwritten. Within a single block, participants were asked to avoid movements to prevent calibration distortion. Each condition in a block included one run of \(\sim\)1.5 min duration. 7 min break came after the third block. Participants were asked to complete the task as quickly as possible, while avoiding the selection of the wrong balls (with a number different from the one that should be next). If the wrong selection occurred, they had to continue the task from the last correctly selected number. The participants were also told not to rush with selecting the first ball to enable them to properly adjust the selection strategy and fully concentrate on the task. The participants were told that for correct selection, they had to look first at the center of the ball and only then execute the confirmation action. The importance of following this instruction was emphasized in the training session and during the experiment is was reminded to the participant. After the main part of the experiment (6 blocks), the participants were asked to think up a short word or sound that, in his opinion, would best serve as a confirmation action. The participants were prompted to try different variants of the confirmation word/sound in an experimental environment without data recording. When they felt ready, the chosen sound was used as the voice confirmation in additional two runs with the same task as in the main part of the experiment (F, \"freeslyte\"). At the end of an experiment, participants were asked to rate the convenience of each task. To do that, they were asked to put a mark on a 10-point Likert linear scale, one per condition, created using Google Forms. For each condition, the question was posed as \"rate the convenience of mode X\", where X was the name of the condition. The scale was labeled with numbers 1 to 10 (left to right), without additional explanation of their meanings; it was supposed that the participants would understand 1 as the lowest and 10 as the highest scores for convenience, respectively (it is common in Russia to perceive higher numbers as grades indicating higher quality or performance). After that, the participants were asked to choose the most convenient confirming action out of four and an additional option \"did not notice differences\". They were also provided with an option to leave a comment about each mode and overall experience from participation (actually, 22 of 23 participants left comments). During task completion (selecting 1, 2,... 10,... 2, 1), for each selection, its time and the corresponding ball number were recorded. Time spent per selection of one ball was computed as the difference between the time of two selections with correct order (1-2, 2-3,... 9-10, 10-9,... 3-2, 2-1). The individual median time was computed over these values per condition and participant.