Contents lists available at ScienceDirect Personality and Individual Differences journal homepage: www.elsevier.com/locate/paid Backward and forward serial recall across modalities: An individual differences perspective ☆ Gilles E. Gignac a,⁎ , Kristof Kovacs b , Matthew R. Reynolds c a University of Western Australia, Perth, Australia b Institute of Psychology, Eszterházy Károly University, Eger, Hungary c Educational Psychology, University of Kansas, Lawrence, KS, USA ARTICLE INFO Keywords: Digit span backward Digit span forward Individual differences Psychometrics Mental rotation ABSTRACT The correlation between Digit Span Forward (DSF) and Digit Span Backward (DSB) scores from the Wechsler scales is moderate (r ≈ .50), but surprisingly small given the highly similar nature of the tests. To-date, little research has examined the association between forward and backward recall across other stimulus modalities (e.g., words, shapes). Furthermore, some experimental research suggests that performance on verbal backward span may be affected differentially by visuospatial ability. Consequently, the purpose of this investigation was to evaluate the factorial validity of forward and backward span across three stimulus modalities: single digits, three-syllable words, and visual shapes. Additionally, a mental rotation test was administered to the participants (N = 211). Based on a factor analysis, four factors were identified: visuospatial memory span, three-syllable word span, DSF, and DSB. The DSF and DSB factors were related moderately at r = .40. Finally, visuospatial ability was not observed to relate to DSB uniquely (λ = .07; BF 01 = 8.65). The results suggest that there may be a process distinction that is unique to the recall of digits in forward and backward formats. However, the process distinction does not appear to be visuospatial ability. 1. Introduction Digit Span Forward (DSF) and Digit Span Backward (DSB) are very si- milar tasks, however, they share approximately only 45% of their true score variance (Gignac, 2015; Wechsler, 2008). Theoretically, it has been con- tended that DSF and DSB tap partly different psychological processes. Specifically, while DSF has been proposed to involve storage and retrieval processes, DSB has been hypothesized to involve additional executive pro- cesses (Oberauer, Süß, Schulze, Wilhelm, & Wittmann, 2000). It has also been proposed that DSB may draw more heavily upon visuospatial pro- cessing, in comparison to DSF (Reynolds, 1997). Although a relatively substantial amount of research has supported the psychometric distinction between forward and backward span with digits, little differential psychology research has been conducted with other types of stimuli. Consequently, the purpose of this investigation was twofold. First, to investigate whether the psychometric distinction between forward span and backward span extends to test content modalities other than digits (i.e., three-syllable words and visual shapes). Additionally, the hypothesis that individual differences in vi- suospatial ability may differentially relate to DSF and DSB was tested. 1.1. Background In the Wechsler scales (e.g., WAIS-IV; Wechsler, 2008), the Digit Span subscale involves the oral presentation of digits to the participant at 1 s intervals. The participant is requested to recall as many of the digits as possible in a certain order. In the forward version of the test, the participant is instructed to recall the digits in the order with which they were presented. In the backward version of the test, the participant is instructed to recall the digits in the reverse order with which they were presented. A non-negligible amount of research has been con- ducted on the distinction between DSF and DSB, particularly within the context of short-term memory capacity (STMC) and working memory capacity (WMC; Conway & Kovacs, 2013). Theoretically, measures of STMC are considered to involve storage and retrieval over a brief period of time (seconds). By contrast, mea- sures of WMC require processing parallel to storage and retrieval (Conway et al., 2005; Redick et al., 2012). For example, WMC tasks have been suggested to require the coordination and transformation of information (Oberauer et al., 2000). A classic measure of WMC is the reading span task, which requires one to read a list of sentences and http://dx.doi.org/10.1016/j.paid.2017.09.033 Received 7 August 2017; Received in revised form 17 September 2017; Accepted 18 September 2017 ☆ Thanks to Mahesh Shankaralingam, Kipling Walker, and Philippe Kilpatrick for testing; the second author's research was supported by grant EFOP-3.6.1-16-2016-00001 (“Complex improvement of research capacities and services at Eszterhazy Karoly University”). ⁎ Corresponding author at: School of Psychological Science, University of Western Australia, 35 Stirling Highway, Crawley, Western Australia 6009, Australia. E-mail address: gilles.gignac@uwa.edu.au (G.E. Gignac). Personality and Individual Differences 121 (2018) 147–151 0191-8869/ © 2017 Elsevier Ltd. All rights reserved. MARK