Does the d2 Test of Attention only assess sustained attention? Evidence of working memory processes involved

The d2 Test of Attention (d2) is widely used for assessing sustained attention and we aimed at verifying whether working memory may be a secondary construct measured by d2. 70 university students were assessed using d2 conventional paper-and-pencil and computational version. The experimental group and control group performed the task with or without target key, respectively. Continuous Performance Test (CPT) and N-back (1 and 2-back) tasks were used to measure sustained attention and working memory, respectively. Computational d2 performance was predicted by CPT (p < .05; R² = .15) in the experimental group, and it was predicted by 2-back (p < .05; R² = .28) in the control group. Conventional d2 performance was predicted by 2-back for both control group (p = .01; R² = .20) and experimental group (p = .02, R² = .17). Results suggest the involvement of working memory in d2, possibly a secondary construct assessed by this instrument.