Complex working memory span tasks have been shown to predict performance on a number of measures of higher-order cognition including fluid abilities. However, exactly why performance on these tasks is related to higher-order cognition is still not known. The present study examined the patterns of errors made on two common complex span tasks. The results suggest that the patterns of errors made on these tasks are an important indicator of the processes that underlie performance and point to the importance of temporal-contextual cues. Furthermore, the individual differences data suggest that low scoring participants do not make more of each type of error at all serial positions, but rather the variability is localized to a few theoretically meaningful positions for each error type. The results suggest that low scoring participants have less precise temporal-contextual cues which leads to an inefficient search of memory.