What happens when you add a ‘not relevant’ response option to the unipolar response scales of personality state items?

What happens when you add a “not relevant” response option to the unipolar response scales of personality state items? In an experimental experience sampling study with a between-person design (total N = 248; n = 3,253 observations), we compared personality states measured with a unipolar response scale including or not including a “not relevant” response option. Overall, “not relevant” responses were quite prevalent but varied between items. Certain characteristics of the situation (particularly sociality) but not of the person predicted the use of the “not relevant” response option. Additionally, means and distributions of personality states significantly differed between the different response scales, but their associations with other relevant constructs did not. Overall, this study emphasizes the importance of systematically addressing how personality states should be measured and provides first evidence that a “not relevant” response option might be an important aspect to consider for the measurement of personality states.