Due to the non-substantiality and abstractness of temporal concepts, people generally think about these abstract concepts by associating with more concrete concept, such as spatial orientation (Haspelmath, 1997; Radden, 2011) . In many languages, the spatial-temporal conceptual metaphor is widely used, e.g., “back in the 60s”, “in the weeks ahead of us” (Clark, 1973; Lakoff & Johnson, 1980b) . The expression of temporal concepts differs across languages. Previous studies have shown that English speakers use the horizontal spatial-temporal metaphor (e.g., “to look back 20 years” to indicate the past). In contrast with English, Chinese native speakers express temporal concept by using vertical metaphor (Boroditsky, 2011; Boroditsky, Fuhrman, & McCormick, 2011; Fuhrman & Boroditsky, 2010; Fuhrman et al., 2011) . For example, “shang4 xing1 qi1” (上星期) indicates “last week” and “xia4 xing1 qi1” (下星期) means “next week”, in which the Chinese character “shang4” (上) stands for “top or upper”, the character “xia4” (下) for “bottom or lower”. If linguistic differences affect conceptualization of temporal concepts, it is likely that speakers across different languages will have different mechanisms behind the spatial-temporal metaphor. Considering the significant divergence in temporal expressions between English and Chinese, exploring spatial-temporal metaphors in Chinese is necessary. In the present study, we examined the mechanism of multi-dimensional spatial-temporal metaphors in Chinese speakers.

A number of studies have reported horizontal spatial-temporal metaphor in English (Boroditsky, 2011; Boroditsky et al., 2011; Fuhrman et al., 2011; Ouellet, Santiago, Jesus Funes, & Lupianez, 2010; Torralbo, Santiago, & Lupiáñez, 2006) . For example, Torralbo et al. (2006) using space-time congruency effect to address the existence of mental timeline that runs from left to right. However representations of linguistic notations differ across languages (Hung, Hung, Tzeng, & Wu, 2008) . Hung et al. (2008) found that different notations of the same concept have flexible mappings within space, influenced by the dominant contexts. They examined the orientation of the mental number line for different numerical notations (e.g., “1”’, “一”, “壹” all mean one) in Chinese speakers. Results showed that Arabic numerals are mentally aligned horizontally, while Chinese number words are aligned vertically. If abstract notations, such as numerical representation, may have different representations in different cultures, we assume that the concept of time can also be influenced by culture. How these processes interact in non-alphabetic language, like Chinese, remains unclear.

Boroditsky (2001) found that Chinese speakers tended to use vertical spatial-temporal metaphor even when they processed temporal concept in English. Participants need to answer some questions about time (e.g. March comes earlier than April.) after processing a horizontal or vertical array of objects. The results showed that Chinese speakers response faster after the priming of vertical arrays. In an additional experiment, native English speakers were trained to talk about time using vertical spatial expressions, then their responses to the temporal became closer to those of Chinese speakers. Therefore, the results from Boroditsky’s studies supported that Chinese speakers tend to think about time vertically, and different languages shape abstract concept differently.

However, Chen (2007) failed to replicate Boroditsky (2001) ’s results, and it suggested that Chinese speakers actually use horizontal spatial metaphors more often than vertical metaphors. Chen utilized the Yahoo search engine and Google News Taiwan to estimate the frequencies of using horizontal and vertical spatial metaphors when Chinese people expressed time. Results clearly showed that horizontal spatial metaphors were used more frequently than vertical spatial metaphors in Chinese speakers. This finding was inconsistent with the results of Boroditsky (2001) . Therefore, Chen concluded that, compared to the English speakers, Chinese speakers do not think about time in a different way, although Chinese speakers use vertical spatial metaphor to express time.

Different tasks and stimuli might cause these inconsistent results. For example, Boroditsky (2001) adopted spatial priming paradigm. In this paradigm, the participants were asked to observe the objects in a horizontal or vertical array, and their reaction times to the temporal relationship judgments were recorded. While this paradigm made participants represent spatial concepts before they process the concept of time. Therefore, this paradigm leads participants to use different spatial frame during the temporal relationship processing. It can not clearly prove the relationships between temporal and spatial representations. Furthermore, although Chen (2007) made some changes in the experimental materials, their participants were Chinese-English bilinguals. English experiences influence their conceptualization even when they are manipulating Chinese. In the present study, though spatial cuing paradigm (Posner, 1980; Posner, Rafal, Choate, & Vaughan, 1985; Ouellet, Santiago, Jesus Funes, & Lupianez, 2010) , we were interesting in examining the psychological impact of the Chinese vertical and horizontal spatial-temporal metaphor, and exploring the dominant dimensions between the two metaphors processing under the Chinese context.

In spatial cuing paradigms, attention is cued to one area of the computer screen, and the responses are influenced by the cue stimulus. Centrally and peripherally presented cues can orient attention (Posner & Cohen, 1984) . Ouellet et al. (2010) used cuing paradigm to demonstrate that temporal words can orient spatial attention. In the present study, participants needed to finish a localization task. Chinese temporal words were utilized in this study to determine whether these words can orient spatial attention or not.

In order to fill these important gaps in the research of temporal-spatial metaphor, current study was conducted to solve three questions as following. 1) in the processing of temporal concepts, do Chinese speakers use the horizontal spatial-temporal metaphor? In experiment 1, we adopted a new paradigm to replicate the findings that horizontal spatial-temporal metaphor exists in Chinese speakers (Boroditsky, 2000, 2001) . 2) In the processing of temporal concepts, do Chinese speakers also use vertical spatial-temporal metaphor? Based on many previous studies (Boroditsky, 2000, 2001; Boroditsky, 2011; Boroditsky et al., 2011; Bottini & Casasanto, 2010; Casasanto & Boroditsky, 2008; Casasanto & Bottini, 2010; Fuhrman & Boroditsky, 2010; Gentner et al., 2002; Lakoff & Johnson, 1980a, 1980b; Merritt et al., 2010; Scott, 1989) , we assumed that Chinese speakers use the vertical spatial-temporal metaphor. 3) If Chinese speakers both have vertical and horizontal metaphors, which one will be the dominant dimension? We also explored the relationship between these two metaphors.

The goal of Experiment 1 was to test whether Chinese temporal reference modulate processing in a concurrent horizontal localization task for speakers of Chinese.

Twenty-seven young adults (mean age = 21 years; 12 females and 15 males) participated in Experiment 1. All the participants were right-handed native speakers of Chinese with normal (or corrected) vision and no reports of neurological disorders. All the participants had passed the national mandarin proficiency test and attained the certificate of level 2 or above, which means they have a relatively high level of Chinese proficiency. As well, all participants gave written informed consent in accordance with the guidelines of the Human Subjects Committee of South China University.

We selected 80 Chinese temporal words from Contemporary Chinese Dictionary (2005). All of the words were dissyllables and none of them contained spatial characters. For example, some temporal words such as “qian2 tian1” (“前天” means the day before yesterday) was not used because the character “qian2” (“前” means in front of something in Chinese) had the meaning of space. Forty-two college students rated each word from 1 to 5 (“1” indicated it was highly consistent with its meaning, and “5” indicated it was highly inconsistent with its meaning) to evaluate its temporal reference. After the evaluation, 48 Chinese temporal words were selected (see Appendix Table A1), Half of the words were past-related (the mean score of the past-related words is 4.60), such as “xi1 ri4” (“昔日” means in past days) and the other half referring to future time (the mean score of the future-related words is 4.24), such as “ming2 tian1” (“明天” means tomorrow or in the following days). All the words are located in the Appendix.

All words were presented in 24 pt. Songti font. The task was programmed in E-prime (Schneider, Eschman, & Zuccolotto, 2002) and conducted on a computer using an Intel Pentium IV PC 1.70 GHz. Stimuli were presented on a 15 inch (38.1 cm) color monitor. The target was a dot of 5 mm diameter, which appeared in one of two 1.3 × 1.3 cm² boxes. The boxes were on both side of the screen (7.39˚ of visual angle; 7.75 cm from the center). All stimuli were presented in white on a black background. The experiment was run in a sound-attenuated, dimly illuminated room.

Participants sat in a quiet room at approximately 60 cm from the screen. Figure 1 illustrated the procedure for Experiment 1. First, a fixation point was presented

for 500 ms, followed by a centrally presented past-related or future-related Chinese word for 1500 ms. Participants were instructed to memorize the temporal reference of the presented words. A blank screen was presented for 500 ms, and two empty square boxes were presented at the left and right positions of the monitor. After 250 ms, a yellow dot flashed for 50 ms in one of the two boxes. The two boxes remained on the screen until the participant responded and timed out at 2300 ms. At this point, participants performed the localization tasks to locate where the dot appeared. The participant should press the “F” key if the dot appeared to the left and the “J” key if it appeared to the right.

In order to make sure that participants kept that temporal representation during the whole trial, after the localization task, a question was set for asking participants whether the word that just appeared refers to the past time or future. Participants were asked to press the “F” or “J” key to indicate a yes or no response. Participants were allowed 4000 ms to give their response, with longer latencies being excluded. Between trials a lank screen was presented for 1000 ms. They were not told about any possible relationship between the cue word and the target location or the target location and the final probe question.

The experiment had two blocks, differing in the mapping of “F” and “J” to yes or no responses. The order of blocks was counterbalanced over participants. Within each block, each experimental word was presented four times, paired with targets at either location, and were presented with both final probe questions. Items across different conditions were presented in a random order. Participants were allowed to take a break between blocks. Each block consisted of 16 practices and 192 experimental trials. The experiment lasted about 45 - 50 minutes.

The results of reaction time in different conditions are summarized in Table 1. Localization errors were 0.43% of trials, and memory errors were 6.7% of trials.

The latency data were submitted to a 2 (Temporal Reference: past/future) × 2 (Target Location: left/right) two-way repeated measures ANOVA. In the latency analysis, the main effect of temporal reference was not significant, F(1,26) = 0.23, MSE = 126.49. The main effect of target location was also not significant, F(1,26) = 0.02, MSE = 6.80. However, we found a significant interaction between temporal reference and target location, F(1,26) = 6.50, MSE = 268.23, p = 0.017.

The simple effect test revealed that when the targets were on the left side, there was a significant difference between different types of temporal reference, F(1,26) = 6.40, MSE = 173.23, p = 0.018, which indicates that the participants responded faster to the past-related words than the future-related words. When the targets were on the right side, there was no significant difference between different temporal references in the subject analysis, F(1,26) = 2.99, MSE = 221.49, p = 0.096, but there was a trend that participants responded faster to the future-related words than the past-related words from descriptive results.

The results in Experiment 1 showed a left-past/right-future (horizontal) facilitating effect for the targets presented at the location cued by the centrally presented Chinese temporal words. Specifically, when the targets were on the left side, the responses to the past-related words were significantly faster than the future-related words, and vice versa. This suggested that temporal reference is able to orient attention along the horizontal axis in Chinese speakers. Further, consistent with Ouellet et al. (2010) , this result supported that Chinese speakers use spatial-temporal metaphor representation in the horizontal axis (i.e., the “left-past/right-future” phenomenon).