The sensor area in the brain remains active during the wake-sleep transition. However, the behavioral mechanisms of sensor sensitivity involved in the transition from a state of wakefulness to a sleep state remain poorly understood. To detect sensitivity index (d') changes during the wake-sleep transition, the present study recorded response times of wakefulness versus wake-sleep transition in 14 healthy undergraduate volunteers. During wake-sleep transition testing, morphological changes in the time courses of behavior response revealed 2 typical phases (stages A and B). In stage A, subject behavior responses exhibited temporal fluctuations, and all subjects displayed a high accuracy rate. In stage B, subjects did not exhibit behavioral responses. The sensitivity index d' during the wake-sleep transition (stage A) was significantly weaker than during wakefulness. Results demonstrated that at the behavioral level, sensation capacity for transfer information from the external world into the internal system significantly decreased during the transition to sleep.