Once upon a time in space: How small eye movements reveal the organising principles of visual working memory

While it is well-established that visual working memory is predominantly organised around spatial information (Awh & Jonides, 2001; Jiang et al., 2000; Pertzov & Husain, 2014; Treisman & Zhang, 2006), even when the exact locations are not directly relevant to the task (Chota et al., 2024; e.g., Draschkow et al., 2022; Liu et al., 2022; Magen & Emmanouil, 2019; van Ede et al., 2019), several key questions remained unanswered. The central question in this dissertation is how space and time act as organising principles in visual working memory, focusing on whether spatial arrangements or temporal sequences structure information, and how this organisation changes over time. This central question was explored through three research questions, investigated across six experiments presented in three empirical chapters (Chapters 2, 3, and 4) of this dissertation. The studies focused on the incidental use of spatial organisation in visual working memory, meaning the unintentional or automatic reliance on spatial information, even when participants are not required to report object locations. The incidental use of space in visual working memory was investigated by tracking spatial biases in eye movements, specifically microsaccades—small, rapid movements that reflect covert shifts in attention (Engbert & Kliegl, 2003; Hafed & Clark, 2002; Yuval-Greenberg et al., 2014). Prior research shows that even when spatial locations are not explicitly relevant, eye movements tend to be biased towards the encoding locations of cued memory objects (Draschkow et al., 2022; Liu et al., 2022; van Ede et al., 2019). These biases suggest that eye movement behaviour can serve as a marker for tracking spatial organisation in visual working memory, even when spatial information is not required for task performance. This dissertation capitalized on these directional microsaccade biases as a direct, time-resolved measure of spatial organisation. Across six experiments, this approach allowed us to examine the persistence of spatial organisation in memory under varying conditions and timeframes.