The dynamic features of long-term habituation of negative emotions: evidence from eye-tracking and hypothalamic-pituitary-adrenal axis research.

Abstract

Objectives: Negative emotional habituation (NEH) plays a crucial role in individuals' survival and adaptation. However, systematic research on long-term negative emotional habituation remains limited. This study aimed to explore the dynamics of the habituation process during prolonged repeated exposure to negative stimuli, from the perspectives of eye-tracking and hypothalamic-pituitary-adrenal (HPA) axis responses.

Methods: Employing a 2 × 7 mixed factorial design, we enrolled 50 healthy male undergraduates and randomly assigned them to moderate- or high-intensity negative-image groups. Negative stimulus intensity served as the between-subject factor, and repeated exposure across seven consecutive daily testing sessions served as the within-subject factor. A single-blind procedure was adopted. Baseline trait anxiety and resilience were assessed. On each testing day, we concurrently obtained subjective ratings (valence, arousal), eye-tracking indices [mean fixation duration (MFD), pupil size], and salivary cortisol samples.

Results: Over the seven-day repetition, valence increased over time while arousal decreased. MFD increased significantly while pupil size decreased significantly, with both indices differing by stimulus intensity. Daily changes in salivary cortisol exhibited a significant downward trend, with a steeper decline under high-intensity negative stimulation. Cross-system coupling varied by intensity: under moderate intensity, valence and cortisol habituation were positively correlated, whereas under high intensity, this association was not significant. Additionally, trait anxiety was significantly negatively correlated with pupil habituation, and resilience moderated the relationship between trait anxiety and valence habituation at a marginally significant level.

Conclusion: These findings indicate that NEH is not a unitary pathway but a dynamic process jointly realized by multiple systems with distinct sensitivities and convergence rhythms. The results reveal nonlinear cross-level coupling in NEH and may inform methodological bases for timing, dose optimization, and process evaluation in exposure-based therapies.