Introduction
Spontaneous eye blink rate (SEBR) is associated with short-term dopaminergic activity, particularly in reward prediction error and motivation. SEBR have been examined within cognitive task paradigms; however, its sensitivity to hedonic responses driven by individual food preferences remains unclear. The present study aimed to investigate the relationship between liking and motivation by whether consumption of a personally preferred beverage modulates SEBR, reflecting hedonic motivation.
Method
In a within-subject design, 60 participants (M = 23.73; SD = 4.85; range: 18-37; 52 women) completed three sessions in a counterbalanced design, during which they consumed plain water, chocolate milk, or a self-chosen favorite beverage. Each session took place on a separate day. Eye blinks were recorded via electromyography (EMG). For each session, 5-minute EMG recordings were obtained both before and after beverage consumption. Blink rate was calculated as the number of blinks per minute during a 5 minute recording. In each session, participants rated liking and desire to consume the beverage using visual analog scales, along with internal state measures (e.g., hunger, stress). Sweet-liking phenotype was evaluated using a sucrose solution.
Results
A repeated measures ANOVA revealed a main effect of time (pre-consumption, post-consumption) (F(1,59)= 4.0751, p= 0.0481). Post-hoc comparisons revealed that SEBR was increased after consumption of favorite drink (t(59)= -2.5971, pbonf= 0.0119). However, we found no significant changes in the chocolate milk condition nor water condition. There was no significant changes in SEBR between session with sugary and non-sugary favorite drinks, nor between sweet taste phenotype. Finally, repeated measures correlation analysis revealed a significant positive correlation between SEBR and liking (rrm(119) = 0.18, p=0.048).
Conclusion
SEBR selectively increased following consumption of subjectively rewarding beverages but not in the water or chocolate milk, suggesting sensitivity to individual hedonic value rather than caloric or sweetness properties. These findings support SEBR as a potential biomarker of reward-related motivational processes.