Sequence memory test: method

What it measures

Visuospatial short-term memory for the serial order of locations (forward spatial span).

Procedure

A 3 x 3 grid of squares. Each try: a short lead-in, then the sequence flashes one square at a time (600 ms on, 300 ms off). The same square never flashes twice in a row but can come back later in the sequence. Then the player taps the squares in the same order; there is no time limit for answering. A wrong tap ends the try at once. The first sequence has 2 squares; a correct try adds 1; each length has 2 tries; 2 failed tries at the same length end the game (maximum 25). No practice. Input: tap or click, or move the keyboard focus to a square and press Enter or Space. On right-to-left pages the grid may be mirrored; squares are stored as cell indexes, so the task is the same.

Parameters

Scoring

Span = the longest sequence reproduced exactly (every tap correct and in order). Also reported: the longest length tried, number of tries and number correct. Unit: steps; higher is better. No player comparison is shown.

Valid-run rules

The page sends every try (squares shown, squares tapped). Tries with a square outside the grid are rejected. The stopping rule is run by the page; the scorer takes the longest correct try in the log. The server rebuilds every run from the raw log (and the run's seed where there is one) and computes the score itself; anything the page says about right or wrong is ignored. A log that breaks the game's rules is rejected, and nothing is stored. Stored runs can carry quality flags that are never shown and never block a result: 10 or more runs from one IP address, a missing visitor id, tab switches, and automation signals (automated browser, impossible speed, no input events, machine-regular timing).

Differences from the classic task

The classic task uses 9 cubes fixed at irregular places on a board; the examiner taps them at about one per second and the person taps them back, with published scoring and norms (Kessels et al. 2000). Here the squares form a regular 3 x 3 grid that is easy to name ('top left'), the sequence flashes on a screen, a square may repeat (not twice in a row), and answers are self-paced taps. The board norms do not apply.

Limitations

Unsupervised browser game; device, screen size and distraction affect the result. Strategies (tracing the path, naming positions) change the score. Scores rise with practice. No norms, no validation of this version, not a clinical test.

Languages and review status

Language-independent stimuli, instructions in all site languages (English plus 99 other languages).