The instrument is an indispensable tool in the experimental approach to psychological problems. In psychological experiments, the researcher can present stimuli and apply experimental treatments with the help of an instrument; irrelevant stimuli can only be eliminated with the help of an instrument to avoid interfering with the results of the experiment. In addition, the instrument helps the researcher to observe, record, and statistically process the data. Even if you use other methods of research, the instrument is also a useful auxiliary tool.