The ordinal distance effect in working memory: does it exist in the absence of confounds?

In most daily-life situations, briefly remembering actions or words is not sufficient to reach a goal. You often have to remember them in a specific order. One behavioural observation of the processing of ordinal information in working memory is the ordinal distance effect. It refers to the facilitation in the ordinal processing of items that are at distant positions in comparison to items close to each other in working memory. So far, the ordinal distance effect has always been investigated with a simultaneous presentation of the items of the memory sequences. Such a presentation created a confound: items distant by their ordinal distance were also distant by their physical distance (i.e., the visuospatial distance between their positions on the screen). In the present study, we investigated whether the ordinal distance effect can be observed in the absence of a physical confound using a sequential presentation of the items of the memory sequence. Our findings revealed a combination of reversed and standard distance effects, unchanged by physical characteristics. The presence of a reversed distance effect suggests that a serial scanning strategy confers an advantage for adjacent items. Different strategies apply to the ordinal judgment of adjacent versus more distant items in verbal working memory. Interestingly, when ruling out the confound of primacy and recency effects, the standard distance effect disappeared while the reversed distance effect remained. Ultimately, our findings question the existence of the ordinal distance effect as a separate effect from other working memory confounds.