Accuracy and Consistency of Visual Analog Scales in Ecological Momentary Assessment and Digital Studies

The ubiquity of digital technologies has increased assessments of thoughts, behaviors, and experiences via electronic devices. Surveys on smartphones or laptops often implement Visual Analogue Scales (VAS), recording responses on a continuous slider (0-100). This is particularly relevant for data collection in daily life, such as ecological momentary assessments (EMA), which repeatedly present items on mobile devices. However, the accuracy of digital VAS has been questioned, particularly regarding tactile precision (e.g., ability to accurately select values) and the consistency of scale interpretation both between- and within-persons over time (e.g., change in scale interpretation or reactivity to repeated measures). Participants (N = 3,761, 67.03% female; Mage = 47.09; SD = 14.41) from the Critical Incidents and Psychological Adaptation (CIPA) Study completed a 30-day EMA assessment. We investigated the accuracy of VAS in terms of (1) tactile precision, (2) respondents’ perception of the neutral point post-EMA, and (3) test-retest consistency of affect ratings pre- and post-EMA. (1) Tactile precision was assessed by asking participants to enter exactly 31 on a 0-100 slider. Results showed high precision (M = 31.01; SD = 3.28; 87.0% scored between 30-32). (2) Between-person agreement on scale perception was assessed by asking participants to determine the neutral score on two affect items (unipolar and bipolar). 82.19% and 88.89% indicated the expected scale midpoint (50 and 0, ± 5) as neutral, respectively. Neutral points deviating from the expected midpoint were correlated (r = .71-.73) with the person-specific means across the EMA period on the respective item. (3) Test-retest consistency was evaluated by asking participants to rate how happy/sad they/others would rate affective events (e.g., a serious argument) pre- and post-EMA. Consistency across time was high (median change = 0-5). Findings support the accuracy and consistency of digital VAS, within the scope of the current methods.