Lost in translation: Mental fatigue induced by simultaneous interpreting impairs working memory and modulates pre-ejection period

This study explores mental fatigue using a professionally relevant and cognitively demanding task: a 33-minute simultaneous interpretation task. While mental fatigue is often characterized by a decline in cognitive performance, its effects on psychophysiological indicators such as the pre-ejection period (PEP)—a marker of sympathetic beta-adrenergic activity and effort mobilization—remain underexplored. Forty-seven participants with a minimum level of B2 in English (mean age = 23.57 years) completed a sequential task protocol comprising a 2-back task performed before and after an interpreting task (fatiguing task) or a comprehension task (less-demanding task). Behavioral results revealed stable translation quality throughout the interpreting task, but the frequency of long pauses (>2 s) increased over time. Post-task performance on the 2-back task significantly declined after the interpreting task compared to the less-demanding condition, indicating mental fatigue. Analysis of PEP data showed a sharp decline in sympathetic beta-adrenergic activity during the first 11 min of interpretation, after which PEP values resembled those of the less-demanding task. These results suggest that interpreters initially mobilize effort, followed by a phase of physiological adaptation marked by reduced sympathetic beta-adrenergic activation. A correlational analysis showed that the decline in performance does not reflect boredom or loss of motivation, but rather a combination of effort disengagement, stress reduction, and cognitive resource management. The study demonstrates that simultaneous interpretation induces measurable mental fatigue observable both behaviorally and physiologically. Moreover, it underscores the complexity of using PEP as a continuous marker of effort in prolonged cognitive tasks. Over time, PEP reflects adaptation. • Simultaneous interpreting induces measurable mental fatigue within 35 min. • Working memory performance is impaired following interpreting effort. • During interpreting, translation quality remains stable despite increasing pauses. • Physiological effort decreases rapidly and then stabilizes suggesting habituation. • Subjective fatigue measures are insufficient when considered in isolation.