The abstract concept of time is mentally represented as a spatially oriented line, with the past associated with the left space and the future associated with the right. Although the line is supposed to be continuous, most available evidence is also consistent with a categorical representation that only discriminates between past and future. The aim of the present study was to test the continuous or categorical nature of the mental timeline. Italian participants judged the temporal reference of 20 temporal expressions by pressing keys on either the left or the right. In Experiment 1 (N = 32), all words were presented at the center of the screen. In Experiment 2 (N = 32), each word was presented on the screen in a central, left, or right position. In Experiment 3 (N = 32), all text was mirror-reversed. In all experiments, participants were asked to place the 20 temporal expressions on a 10-cm line. The results showed a clear Spatial–TEmporal Association of Response Codes (STEARC) effect which did not vary in strength depending on the location of the temporal expressions on the line. However, there was also a clear Distance effect: latencies were slower for words that were closer to the present than further away. We conclude that the mental timeline is a continuous representation that can be used in a categorical way when an explicit past vs. future discrimination is required by the task.

时间的抽象概念在精神上被表示为一条空间定向的线，过去与左侧空间相关联，未来与右侧相关联。尽管这条线应该是连续的，但大多数可用的证据也与仅区分过去和未来的分类表示一致。本研究的目的是测试心理时间线的连续性或分类性。意大利参与者通过按左右键来判断 20 个时间表达的时间参考。在实验 1（N  = 32）中，所有单词都显示在屏幕中央。在实验 2 ( N  = 32) 中，每个单词在屏幕上显示在中央、左侧或右侧的位置。在实验 3 ( N = 32），所有文本都是镜像反转的。在所有实验中，参与者被要求将 20 个时间表达放在一条 10 厘米的线上。结果显示出明显的空间-时间响应代码关联 (STEARC)效应，其强度不会因线上时间表达式的位置而异。然而，也有明显的距离效应：离现在更近的词比更远的词延迟更慢。我们得出结论，当任务需要明确的过去与未来的区分时，心理时间线是一种连续的表示，可以以分类的方式使用。