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

The ubiquity of digital technologies has increased the assessment of individuals' thoughts, behaviors, and experiences via electronic devices. Surveys on smartphones or laptops often implement Visual Analogue Scales (VAS), recording responses on a continuous slider from 0 to 100. This is particularly relevant for data collection in daily life, such as ecological momentary assessments (EMA), repeatedly presenting items on mobile devices. However, the accuracy of digital VAS has been questioned, particularly regarding tactile precision (e.g., finger-to-screen size ratio), the consistency of scale interpretation between respondents, and over time (e.g., reactivity to repeated measurement). 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, and (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) The neutral point was assessed by asking participants to indicate the score for feeling neutral on two affect items (unipolar and bipolar), with 82.19% and 88.89% indicating the scale midpoint (50 and 0, ± 5) as neutral point respectively. Neutral points deviating from the midpoint were strongly 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 be in response to 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 and alleviate several key concerns about potential inaccuracy.