Visual memory.
Squares light up one after another: can you remember the same order, and then the reverse?
Original study
- Corsi, P. M. (1972). Human memory and the medial temporal region of the brain [Doktora tezi, McGill University]. Source
- Milner, B. (1971). Interhemispheric differences in the localization of psychological processes in man. British Medical Bulletin, 27(3), 272–277. Source
- Berch, D. B., Krikorian, R., & Huha, E. M. (1998). The Corsi block-tapping task: Methodological and theoretical considerations. Brain and Cognition, 38(3), 317–338. Source
- Kessels, R. P. C., van Zandvoort, M. J. E., Postma, A., Kappelle, L. J., & de Haan, E. H. F. (2000). The Corsi Block-Tapping Task: Standardization and normative data. Applied Neuropsychology, 7(4), 252–258. Source
- Kessels, R. P. C., van den Berg, E., Ruis, C., & Brands, A. M. A. (2008). The backward span of the Corsi Block-Tapping Task and its association with the WAIS-III Digit Span. Assessment, 15(4), 426–434. Source
- Brunetti, R., Del Gatto, C., & Delogu, F. (2014). eCorsi: Implementation and testing of the Corsi block-tapping task for digital tablets. Frontiers in Psychology, 5, 939. See also: Claessen, M. H. G., van der Ham, I. J. M., & van Zandvoort, M. J. E. (2015). Computerization of the standard Corsi Block-Tapping Task affects its underlying cognitive concepts: A pilot study. Applied Neuropsychology: Adult, 22(3), 180–188. https://doi.org/10.1080/23279095.2014.892488 Source
- Farrell Pagulayan, K., Busch, R. M., Medina, K. L., Bartok, J. A., & Krikorian, R. (2006). Developmental normative data for the Corsi Block-Tapping task. Journal of Clinical and Experimental Neuropsychology, 28(6), 1043–1052. Source
Our adaptation
A screen adaptation of Corsi's (1972) block-tapping task. Nine squares sit in a fixed, irregular layout; each square lights for 700 ms with 300 ms between squares. In round 1 the squares are tapped in the order they lit (forward), in round 2 in reverse (backward). Both rounds start with sequences of 2; each length has two trials, the sequence grows by one square if at least one is correct, and the round ends if both are wrong. Taps are captured with the pointerdown event.
Differences from the original study
- Squares on a screen are tapped instead of wooden blocks; Claessen et al. (2015) found lower forward accuracy on a tablet version.
- Layout and the path of the sequences affect difficulty; scores from different implementations are not directly comparable.
Measured variables
The columns of the open data file. List fields are expanded into numbered columns (for example rt_60, est_3); JSON columns contain only numbers and fixed stimulus names.
| Column | Type | Description |
|---|---|---|
fwd | integer | Forward span: longest sequence with at least one correct trial. |
bwd | integer | Backward span: longest sequence with at least one correct trial. |
total | integer | Sum of forward and backward span. |
trials | JSON | Trials: [{"d": f = forward / b = backward, "len": sequence length, "ok": correct}], in presentation order. |
Columns present in every file (14)
row_id | string | Row code. Regenerated at random in every release; it does not identify a person and cannot be matched across releases or experiments. |
experiment | string | Short name of the experiment (URL slug). |
experiment_version | integer | Version of the answer format. For experiments whose format changed, only the current format is published. |
date | YYYY-MM-DD | YYYY-Www | YYYY-MM | Day the answer was given (Istanbul time). If fewer than 5 answers share the same day, language and device, it is coarsened to the ISO week, and to the month if that is still too few. |
date_precision | day | week | month | Precision of the date column. |
lang | tr | en | (boş) | Interface language. Language recording started in the first week of October 2026; for earlier answers it is known only in experiments whose stimuli depend on the language, and empty otherwise. |
device | desktop | mobile | tablet | (boş) | Device class reported by the browser (class only; browser details are neither stored here nor published). |
source | site | embed | Where the answer came from: the balabs site or the experiment embedded on another site. The embedding site is not published. |
mode | free | daily | challenge | race | session | (boş) | Play mode in scored experiments: free play, daily round, challenge, race room, experiment session. Empty for unscored experiments and for older answers that did not store it. |
color_vision | normal | rg | by | contrast | (boş) | In color-based experiments, the color vision mode the participant chose: normal, red-green, blue-yellow or high contrast. Stimuli are generated along different axes per mode, so compare within a mode. Empty for other experiments. |
first_play | 1 | Every row is a participant’s first play of this experiment (always 1). Replays are stored only as leaderboard scores and are not part of the open data. |
seen_before | yes | no | unsure | (boş) | Participant’s own report of whether they had seen this experiment or its known answer before (in experiments that ask). |
duration_s | number | Time from the start of the experiment to submitting the answer, in seconds (measured in the browser, 0.1 s). |
play_score | number | Leaderboard score of the first play (scored experiments; defined on the method card). Empty for unscored experiments. |
Exclusion criteria
The server checks the forward and backward span against the trial records (longest correct sequence in each direction); inconsistent submissions are rejected. Spans must be between 0 and 9.
- Only each participant's first answer to this experiment; replays are not included.
- Simulated rows, bots, banned and sample accounts are not included.
- Answers before 3 October 2026 are not included (the first day the open data notice was live).
Scoring
Leaderboard score: forward + backward span; higher is better.
Leaderboard measure: span (higher is better). The play_score column in the open data is this score for the first play.
Version notes
- October 2026
Memory span is now checked against the trial records (longest error-free forward and backward sequence); inconsistent submissions are rejected.
- October 2026
This experiment started storing the play mode (free, daily, challenge, race, session) with the answer; the mode column is empty for earlier answers.
- October 2026
The interface language (lang) started being stored with each answer; for earlier answers it is known only in experiments whose stimuli depend on the language, and empty otherwise.