Daily life is filled with activities that require holding sequences in memory for a short period of time. It has been proposed that this process is supported by the spatialization of working memory (WM), whereby items are maintained on a mental whiteboard with earlier items in the sequence localized towards the left and later items localized towards the right. Support for this hypothesis comes from a behavioral phenomenon – the Spatial Position Association of Response Codes (SPoARC) effect – in which participants are faster to make judgments about items earlier in a sequence with their left hand, and faster to make judgments about items later in a sequence with their right hand. The research in this dissertation addresses the behavioral underpinnings and neural correlates of the SPoARC effect from an individual differences perspective. For the behavioral underpinnings, I investigated the relationship between the SPoARC effect, different WM capacities, and different aspects of spatial attention using a multilevel modeling approach. A larger SPoARC effect was found to be associated with a higher capacity to maintain item information in spatial WM, and in turn, was conducive to a higher capacity to maintain serial order information in verbal WM; but there was no relationship with other spatial attention capacities. For the neural correlates, I examined the mesoscale network modularity with graph theory analysis on resting-state functional connectivity. A less modular, more interactive organization of the neural regions that mediate verbal serial order WM and spatial processing (spatial attention or spatial WM) were beneficial to a larger SPoARC effect. The findings elucidate the spatial processing involved in the SPoARC effect and extend the mechanistic understanding of the previous theoretical model. This research underscores the importance of using different methodological approaches to reach a converging theoretical framework. The cognitive and neurobiological profiles of the SPoARC effect and its implication for serial order maintenance in WM are discussed.