Feature misbinding underlying serial-order effects of visuospatial working memory

The accurate processing of incoming visual information in serial order is fundamental to visual cognition. Prior studies have demonstrated primacy and recency effects in tasks requiring the serial recall of visual stimuli such as letters, digits, words, or locations. However, there is ongoing debate about whether these primacy/recency effects on working memory retrieval reflect variable representational precision for multiple items in memory or misbinding of item features (e.g., location) and their ordinal position. This study sought to examine potential sources contributing to serial-position effects in visuospatial working memory using eye tracking and statistical modeling approaches. In two eye-tracking experiments, we measured the latency and endpoint error of serial-order memory-guided saccades under varying cue conditions (order cue vs. quadrant cue) from a total of 92 participants. The first (primary) memory-guided saccade showed primacy and recency effects on endpoint error, latency, and transposition error in the order-cue condition, but not in the quadrant-cue condition. Probabilistic modeling of memory-guided saccade distribution showed a better fit of a standard (non-swapping) model to the quadrant-cue condition and a swap model to the order-cue condition. These findings indicate that visuospatial working memory representation varies across serial positions primarily due to location-serial-position misbinding rather than variable memory precision about location.