Do Chinese and English speakers think about time differently? Inconsistent findings have been reported even when the same paradigms were used. One of the factors that might have contributed to the inconsistency is participants’ reading experience of horizontal and vertical texts. The present study manipulated this factor experimentally by randomly assigning Chinese participants from Taiwan and China to a reading task involving horizontally or vertically arranged texts. A temporal judgment task (spatial-temporal association of response codes or STARC) followed the reading task immediately. It asked the participants to judge if the event depicted in a second picture occurred earlier or later than that depicted in the first. Responses were faster when the left keys represented the ‘earlier’ responses than when the right keys did (a STARC effect). Half of the participants responded with a horizontally oriented keypad while the rest with a vertically oriented keypad. For the Taiwan participants, the STARC effect was greater when the response keys were oriented vertically than horizontally, but no difference was observed for the China participants. The results also showed that both immediate and lifetime reading experiences modulated the vertical bias. For the Taiwan participants, the vertical bias was strong following the vertical prime, but it disappeared following the horizontal prime. For the China participants, the horizontal prime led to a nonsignificant vertical bias whereas the vertical prime brought about a significant horizontal bias. A questionnaire administered upon completion of the STARC task indicates that the two groups of participants had similar lifetime experience of reading horizontal texts, but the Taiwan participants read vertical texts in their life far more frequently than the China participants. We conclude that the directionality of orthography and speakers’ (immediate and lifetime) reading experience can better explain the vertical bias (or the lack of it) in the Chinese speakers.