The Temporal Doppler Effect (the subjective perception that the past is further away than the future) couldn't be replicated; in some cases, the correlations were significant in the opposite direction

Is the past farther than the future? A registered replication and test of the time-expansion hypothesis based on the filling rate of duration. Qinjing Zhang et al. Cortex, October 23 2022. https://doi.org/10.1016/j.cortex.2022.10.005

Abstract: Caruso et al. (2013) reported the Temporal Doppler Effect (TDE), in which people feel that the past is farther than the future. In this study, we made two high-power (N = 2244 in total), direct replication studies of Caruso et al., and additionally examined whether illusory temporal expansion, depending on the degree of fulfillment in durations, is related to the TDE. We predicted that the past would be felt farther than the future because the filling rate of duration of the past should be higher than that of the future. The results showed that psychological distance was significantly closer in the past than in the future and was inconsistently correlated with the filling rate of duration or the number and length of events and errands. Further, in some cases, the correlations were significant in the opposite direction of the predictions. Overall, our results did not replicate the previous findings but were reversed, and the filling rate of duration failed to explain the psychological distance. Based on these findings, we highlight the aspects that need to be clarified in future TDE studies.

Keywords: Temporal Doppler Effectfilling rate of durationpsychological distancefilled-duration illusion

6. General Discussion

This is a registered report per the Caruso et al.’s (2013) Studies 1a and 1b, which aimed to examine differences in psychological distance underlying past and future conditions (TDE) and to investigate the relationship between psychological distance and the filling rate of duration inspired by FDI studies in time perception. In our Study 1, the results showed that the past felt closer than the future, which is the opposite of H1, and suggested a failure to replicate the Caruso et al.’s (2013) Study 1a. We also examined whether the TDE could be explained by the filling rate of duration. The results indicated that the filling rate of duration was higher in the past than in the future, as predicted. The correlation between psychological distance and the length of errands and events was significantly positive, however, no significant correlation between psychological distance and the filling rate of duration, the number of errands and events were observed. In other words, our hypothesis that the filling rate of duration was higher in the past than in the future and had an effect on the TDE was not supported as a whole.

Next, in our Study 2, in which the time scale was changed from 1 month to 1 year, the results also indicated that the past felt closer than the future. It showed an opposite direction from H1 and suggested that the Caruso et al.’s (2013) Study 1b was not replicated. We then examined whether the TDE could be explained by the filling rate of duration. In H2-1, the filling rate of duration was higher in the past than in the future. In H2-2, there was a significant negative correlation between psychological distance and the filling rate of duration. In other words, our hypothesis that the filling rate of duration was higher in the past than in the future and that this had an effect on the TDE was not supported as a whole.

One of the aims of this study was to contribute to the robustness and transparency of the TDE research using the Registered Reports system. Although approximately 1000 people participated in Studies 1 and 2 to increase statistical power of the test, the TDE was not replicated (rather, our results were the opposite of the original research).

Investigating what contributed to these discrepancies in the results between the studies would be beneficial in forming a better understanding of the TDE. Indeed, there are several differences in the research methodology between Caruso et al. (2013) and our study: (i) our experiment used crowdsourcing services rather than face-to-face methods; (ii) the instructions and questionnaires were written in Japanese, and only Japanese people participated in the experiment; and (iii) the experiment was conducted during the COVID-19 pandemic. In the following section, we discuss these differences and how they influence the replication of the TDE.

First, unlike the previous study, we used crowdsourcing to recruit participants. Previous studies show that even for demanding cognitive and perceptual experiments, web experiments do not reduce data quality (Germine et al., 2012). Therefore, it is unlikely that the crowdsourced web experiment, especially with the present less demanding task compared with perceptual experiments, caused any significant deterioration in measurement accuracy or failed to detect any true effects that should have existed. In addition, we excluded data from participants who did not respond properly to the ACQ to ensure the quality of our data. These points led us to consider that the difference in the experimental platform did not play a major role in the present failure to replicate Caruso et al. (2013).

Second, several linguistic and cultural differences exist. In Japanese, the past is sometimes expressed as “mae (前)” which means “before” as an expression of time, while it also means “front” referring to a spatial direction, and the future as “ato (後)” which means both “after” and “back.” This suggests that the spatio-temporal metaphors in Japanese and English may be reversed. This reversal in the spatio-temporal metaphors may have led to the different results on the TDE between the previous and present studies. It should be noted that even if the spatio-temporal metaphors are reversed between Japanese and English speakers, it does not affect the original explanation of the TDE that the future approaches the present and the past moves away from it. This is because the mechanism proposed by Caruso et al. (2013), as an analogy to the Doppler effect in physics, focuses on temporal distance, that is, whether the past or future approaches or moves away from the present on the temporal dimension. In their explanation, the movement on the psychological temporal dimension is critical, regardless of the spatial metaphor unique to Japanese. Therefore, the TDE mechanism proposed by Caruso et al. cannot explain our results from the Japanese sample. Nevertheless, cross-cultural comparative studies focusing more on this point are warranted since the contributions of language and culture to the TDE, or possibly the mental timeline (Starr & Srinivasan, 2021), are important for clarifying its cognitive mechanism and generalizability.

In terms of conducting the experiment during the COVID-19 pandemic, the tendency to think about the past rather than the uncertain future may have strengthened, which may have led to an opposite result to that of Caruso et al. (2013). Previous findings showing that the tendency to think about the past, such as nostalgia, increases when psychological threat and loneliness are high, can suggest this possibility (Routledge et al., 2013; Wildschut et al., 2006, 2010). Indeed, the findings of this study that the filling rate of duration is higher in the past than in the future seem to be part of the tendency that the phenomenon of thinking more about the past rather than the uncertain future was strengthened during the COVID-19. However, since these results are not a direct indicator of the aforementioned time orientation, and this study was the first to report on the TDE during the pandemic, this influence cannot be concluded. It should be discussed from the integrated view of this study and subsequent studies that examine the TDE during the pandemic. It should also be noted that a comparison with previous studies examining the TDE before the pandemic is necessary in such cases.

Thus, more evidence is needed to determine whether the methodological and contextual differences between our study and Caruso et al. (2013) influence the TDE, as well as to understand the underlying mechanism. Moreover, the mechanism of the TDE needs to be discussed according to the differences mentioned above. This study attempts to explain the TDE based on the filling rate of duration. Although the filling rate of duration was higher in the past than in the future, as we predicted, the correlation with psychological distance was extremely weak in Study 1, and contrary to our prediction, a negative correlation was observed in Study 2. These results suggest that it is not appropriate to explain the TDE based on the filling rate of duration. However, this mechanism-oriented approach is crucial in itself, and rather than just examining whether the phenomenon is related to some factors, as in previous TDE studies, future TDE studies should focus more on the underlying cognitive mechanism. Importantly, this requires the TDE to be replicated robustly. Moreover, because there is a possibility that the TDE may not be replicated, as in our study, it is appropriate to conduct the study as a registered report to prevent publication bias.

In the present study, the TDE was not replicated as already known (although there are several possible influences) and the mechanism remains unclear. Given the sample size, the TDE does not appear to be a robust and culturally universal phenomenon, and there still seems to be room for reconsideration of this phenomenon and its mechanism.