“…Third, the present study did not consider the potential effects of other endogenous variables, such as positive and negative affect, in delay discounting. Given the previous finding that negative affect leads to less steep discounting (Yamane, Takahashi, Kamesaka, Tsutsui, & Ohtake, 2013), the cultural difference in delay discounting might be caused by an individual's subjective feelings, which the present study did not examine. Fourth, given a suggestion that biases in time perception influence impulsivity in delay discounting (Takahashi, 2005), the current findings might partially result from cultural differences in time perception, which were not considered in the present study.…”