Abstract
Short-form video use is associated with poor emotional well-being, yet its short-term temporal relationship with affect in daily life remains unclear. We conducted a 14-day ecological momentary assessment (EMA) study to examine bidirectional associations between reported short-form video use (SV) and affective states, seperate within-person fluctuations from between-person differences, and assess whether the daily SV use rate was associated with affective inertia and innovation variability. A total of 134 Chinese university students contributed 17,514 valid EMA responses, yielding 14,899 complete same-day lag-1 transitions. Using Bayesian dynamic structural equation modeling, we identified several associations at the momentary timescale: 1) SV use during the preceding survey interval was associated with lower positive affect at the subsequent assessment; 2) SV use and above-zero negative affect intensity were positively associated in both directions, whereas no credible association was observed between SV use and the all-zero negative affect state. At the daily timescale: 1) Daily SV use rate was not associated with mean levels of either positive or negative affect; 2) Higher daily SV use was associated with weaker inertia in both positive affect and above-zero negative affect, as well as lower innovation variability in positive affect. In conclusion, our findings highlight the dynamic associations between SV use and affect across multiple timescales. These findings motivate further research using objective use logs and designs capable of supporting causal inference.