Spatial Span
Spatial span is a visuospatial analogue of the digit span test. This test was conducted at 90 min of post-d-amphetamine administration (0.45 mg/kg) and at 60 min post-caffeine administration. For each trial, ten randomly arranged blue squares (Psychcorp Mark) were shown on the table. The task began with the simplest level of a two-box sequence. After each successful trial, the number of boxes in the sequence was increased by one to a maximum of nine. There were eight items, each with two trials of the same box number (i.e., a total of 16 trials). There were four delay conditions (0, 4, 6, and 8 s delay): the participant was asked to touch the boxes in the same order (forward) right after the examiner (0 s delay), and repeated for 4, 6, and 8 s delays (but different compositions). In addition to the intrinsic differences among tasks, delay condition between encoding and maintenance phase might be a key factor in WM performance [