Those parts of life that most occupy our thoughts are often those that are (or seem) unfinished. The partly-composed letter, the half-completed crossword puzzle, the interrupted dinner preparation: these events seem to stick in our minds, much more so than events that are either completed or unstarted. In this work, we demonstrate how unfinishedness may be privileged in the mind at an even deeper level, being extracted at the level of visual processing itself. Such a possibility has rich philosophical connections, especially as it relates to debates about the content and richness of perception (e.g., Siegel & Byrne, 2017). The present work adds a new twist to this classic philosophical question: beyond factors such as causality or intuitive physics, perception may also traffic in a property that is more typically associated with higher-level goals or motivation.

The tension we feel from unfinished things was first explored empirically in the 1930s, in the “Zeigarnik effect” (Zeigarnik, 1938). Subjects completed various tasks, but were interrupted by an experimenter and kept from completing some of them. Afterwards, subjects were asked to recall as many tasks as possible, and those left unfinished were more likely to be remembered. Unfinishedness has far-reaching consequences: unfinished tasks reduce cognitive flexibility (Freeman & Muraven, 2010), impair sleep (Syrek & Antoni, 2014), and reduce work satisfaction (Weigelt et al., 2019). This property of “unfinishedness” may be one of the origins of ruminative thought (e.g. Gold & Wegner, 1995; Watkins, 2008).

Explanations for the Zeigarnik effect and its consequences are varied, but what perhaps unites them is a focus on high-level social motivations. People intrinsically value tasks that are nearly complete or able to be completed (Converse et al., 2023; Ruan et al., 2024), and such effects may vary as a function of goal salience (Eitam et al., 2013; Ferguson & Cone, 2013), motivation (Atkinson, 1953), or personality (Di Paula & Campbell, 2002; Martin & Davidson, 1964). Here, in contrast, we explore a different sort of explanation, based on a much lower-level form of unfinishedness. Observers merely watched animations of simple shapes (as depicted in Figure 1). On each trial, they viewed a path that gradually unfolded through a 2D maze, in the form of either a simple line that moved from a salient ‘startpoint’ to an ‘endpoint’ (the small discs in Figure 1). As the path unfolded, probes (the colored squares in Figure 1) appeared at haphazard times, and observers later reproduced the probes’ positions. Critically, the unfolding path sometimes reached its endpoint, or sometimes stopped shortly before this point. Thus, observers experienced unfinishedness that was visual (rather than cognitive), passive (rather than active), and spontaneous (rather than embedded in semantically-laden tasks and obligations). Would this still yield a type of visual Zeigarnik effect?

We first tested gradually unfolding paths while controlling for lower-level properties of speed (Experiment 1), as well as path lengths and durations (Experiment 2). Results showed more precise reproductions on ‘unfinished’ trials. To ensure that these effects were not explained by another powerful visual property of connectedness (since the two discs in ‘completed’ trials were connected into a single contour), we replicated these effects beyond fully visible paths (as in Figure 1) by studying dots which moved through mazes without leaving traces (Experiment 3).

These effects, however, can be interpreted as either an unfinishedness benefit or a completion cost. We then replicated our effects while also adding a baseline condition in which we simply removed the endpoint (so that there was no basis on which to perceive a path as either unfinished or complete; Experiment 4). Reproductions were again more precise for ‘unfinished’ trials — even relative to the baseline, while reproductions did not differ for ‘completed’ versus baseline trials. This suggests that previous effects reflect a specific benefit to unfinishedness.

Altogether, the current study shows how we spontaneously extract the property of ‘unfinishedness’ — and that we do so even for exceptionally simple visual motions, and even when this property is entirely task-irrelevant. ​​Moreover, this property has an outsize impact on visual working memory, independent of explicit goals and obligations. When an event is unfinished, its information may be actively maintained in working memory, since this information can still be relevant for what is to come next. This may be especially true in visual perception, where anticipating what is about to unfold can be critical for guiding online behavior. Thus, in perception, unfinished events may not simply reflect the frustrated unresolved goals of the past — rather they may represent possibilities of what is still about to come.

The events that occupy our thoughts in an especially persistent way are often those that are unfinished -- half-written papers, unfolded laundry, and items not yet crossed off from to-do lists. And this factor has also been emphasized in work within higher-level cognition, as in the "Zeigarnik effect": when people carry out various tasks, but some are never finished due to extrinsic interruptions, memory tends to be better for those tasks that were unfinished. But just how foundational is this sort of "unfinishedness" in mental life? Might such unfinishedness be spontaneously extracted and prioritized even in lower-level visual processing? To explore this, we had observers watch animations in which a dot moved through a maze, starting at one disc (the 'startpoint') and moving toward another disc (the 'endpoint'). We tested the fidelity of visual memory by having probes (colored squares) appear briefly along the dot's path; after the dot finished moving, observers simply had to indicate where the probes had appeared. On 'Completed' trials, the motion ended when the dot reached the endpoint, but on 'Unfinished' trials, the motion ended shortly before the dot reached the endpoint. Although this manipulation was entirely task-irrelevant, it nevertheless had a powerful influence on visual memory: observers placed probes much closer to their correct locations on Unfinished trials. This same pattern held across several different experiments, even while carefully controlling for various lower-level properties of the displays (such as the speed and duration of the dot's motion). And the effect also generalized across different types of displays (e.g. also replicating when the moving dot left a visible trace). This new type of Visual Zeigarnik Effect suggests that the unfinishedness of events is not just a matter of higher-level thought and motivation, but can also be extracted as a part of visual perception itself.