The Corsi Block Span (Forward) task is the standard measure of visuospatial short-term memory capacity. Nine grey blocks are arranged in a fixed irregular pattern on screen, mirroring Corsi's (1972) original wooden board. On each trial, the blocks light up one at a time in a sequence. Immediately after the last block fades, the participant clicks the blocks in the same order they were highlighted.

The task begins at span 2 (two blocks) and increases through spans 3, 4, 5, 6, 7, 8, and 9. Two trials are presented at each span level. Performance is assessed as the longest span at which the participant recalls correctly on at least one of two trials — the Corsi block span. The task ends automatically after both trials at a given span level are failed.

This implementation uses 2 practice trials (span 2, with feedback) followed by the main task (up to 16 trials: 2 per span level from 2 to 9). Each block is highlighted for 1000 ms, separated by a 400 ms blank inter-stimulus interval. After each practice trial, participants see a correct/incorrect indicator so they understand the response format before data collection begins.