The mental timeline is used as a memory strategy

Remembering the temporal context of events is difficult across the lifespan. Across many cultures and languages, people get around this problem by grounding representations of temporal events and temporal order in space. Spatial representations of time are ubiquitous, both as external tools such as calendars and in the form of a mental timeline, a linear projection of temporal order onto space. Recent research suggests that people spontaneously draw on the mental timeline to remember temporal order. However, it is unknown how the mental timeline is utilized during the encoding and retrieval of temporal information. Here, we probed how the mental timeline aids temporal memory by combining behavioral, eye-tracking, and pupillometry methods. Participants completed a visuospatial episodic memory task in which they encoded the spatial location and temporal order of images presented in sequences that were either congruent or incongruent with the mental timeline. Participants showed a strong temporal memory advantage for images presented congruent with the mental timeline compared to images presented incongruent with the mental timeline. Pupil dilation patterns revealed that information presented in congruent trials was more easily encoded and maintained in memory. Gaze movement patterns revealed that participants more accurately remembered and referenced the spatial locations of the images when recalling temporal order. Both gaze and error patterns suggested that the temporal memory benefit from congruent trials may be due to the salience of spatial memory. These findings suggest that engaging the mental timeline may allow people to leverage robust spatial memory abilities to support temporal memory.