 Thus, the learning efficiency degree {\cal L}_e (taking into consideration both timing and strength of CR) for the CR increases with learning trial , and eventually it becomes saturated.
<clarity>  Thus, the learning efficiency degree {\cal L}_e (taking into consideration both timing and strength of CR) for the CR increases with learning trial , and eventually it becomes saturated.
 Thus, the learning efficiency degree {\cal L}_e (taking into consideration both timing and strength of CR) for the CR is increased , and eventually it becomes saturated.