Rebuild the shape.
After seeing a shape for 2.5 seconds, how accurately can you rebuild its position, angle and size from memory?
Original study
- Appelle, S. (1972). Perception and discrimination as a function of stimulus orientation: The "oblique effect" in man and animals. Psychological Bulletin, 78(4), 266–278. Source
- Wei, X.-X., & Stocker, A. A. (2015). A Bayesian observer model constrained by efficient coding can explain 'anti-Bayesian' percepts. Nature Neuroscience, 18(10), 1509–1517. Source
- Hollingworth, H. L. (1910). The central tendency of judgment. The Journal of Philosophy, Psychology and Scientific Methods, 7(17), 461–469. Source
- Huttenlocher, J., Hedges, L. V., & Duncan, S. (1991). Categories and particulars: Prototype effects in estimating spatial location. Psychological Review, 98(3), 352–376. Source
- Brady, T. F., Konkle, T., & Alvarez, G. A. (2011). A review of visual memory capacity: Beyond individual items and toward structured representations. Journal of Vision, 11(5), 4. Source
- Shepard, R. N., & Metzler, J. (1971). Mental rotation of three-dimensional objects. Science, 171(3972), 701–703. Source
Our adaptation
A short-term memory task for a shape's position, angle and size (inspired by the category work of Huttenlocher et al. and the oblique effect). In each round one of five asymmetric shapes appears for 2.5 seconds at a random position, size (0.65–1.45 times normal) and angle; after a 0.4-second blank the same shape appears in the center at normal size and a random angle, and is dragged and rotated into place.
Differences from the original study
- The shape always starts in the center at normal size; a drift toward the center and normal size can partly come from the starting point.
- The oblique effect was mostly found with lines and gratings; here the pose of a whole shape is measured.
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 |
|---|---|---|
t | JSON | Rounds: [[shape, target x, target y, target size, target angle, answer x, answer y, answer size, answer angle, time in ms] × 5] (position relative to the field width). |
sub | JSON | Sub-scores per round: [position, angle, size] (each 0–10). |
pts_1 | number | Round score: mean of the three sub-scores. (item 1) |
pts_2 | number | Round score: mean of the three sub-scores. (item 2) |
pts_3 | number | Round score: mean of the three sub-scores. (item 3) |
pts_4 | number | Round score: mean of the three sub-scores. (item 4) |
pts_5 | number | Round score: mean of the three sub-scores. (item 5) |
points | number | Total score (0–50). |
pos | number | Mean position sub-score. |
ang | number | Mean angle sub-score. |
size | number | Mean size sub-score. |
near | number | Mean angle error (°) in rounds whose target angle is within 15° of horizontal/vertical. |
obl | number | Mean angle error (°) in rounds with oblique targets. |
sslope | number | Log-log slope of answer size against target size (below 1 means sizes were pulled toward the middle). |
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 range-checks all values of the five rounds and computes errors and scores itself.
- 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: total score (0–50). Sub-scores: position 10 / (1 + (d / 0.06)^1.6), angle 10 / (1 + (a / 14)^1.6), size 10 / (1 + (|ln ratio| / 0.12)^1.6). Higher is better.
Leaderboard measure: shape memory (higher is better). The play_score column in the open data is this score for the first play.
Version notes
- 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.