PEBL Hub — IRB Fact Sheet — 2026-08-23
Symmetry Span Task
working memory
visuospatial processing
executive function
dual-task processing
spatial memory
Category:Memory
Duration:~15 minutes
Ages:18+
Populations:adults, research, clinical
Parameters:9 configurable parameters: feedbacktimeout (1500ms), distractfile (distraction.csv), batterythreshold (0.85), batteryFeedback (1), distracttimeoutminimum (1000ms), distracttimeoutmultiplier (2.5), requirethresholdprebattery (1), allowsecondchance (1), responsemode (none), testreps (3), testminsize (2), testmaxsize (5)
Version:2.4
Description
Visuospatial working memory span task requiring participants to remember spatial locations while making symmetry judgments.
Participants judge whether 8x8 grid patterns are vertically symmetrical (True/False), then see a red square flash in one cell of a 4x4 grid to remember. After a series of symmetry-square pairs (set size 2-5), they recall the square locations in order by clicking on the grid. The task includes practice blocks for spatial recall only, symmetry judgments only, and combined trials. Symmetry performance is monitored and participants must maintain 85% accuracy on symmetry judgments to ensure divided attention. If threshold is not met, participants may repeat practice with feedback. The main test consists of sets of 3 trials at each set size (2, 3, 4, 5) in random order.
Measures: Visuospatial working memory span, executive function, dual-task processing, symmetry processing, spatial memory
Notes
- Task follows Kane et al. (2004) methodology with 2-5 square set sizes
- Symmetry accuracy threshold (default 85%) enforced to ensure divided attention
- Adaptive symmetry timeout calculated from practice: mean + 2.5*SD with 1000ms minimum
- Practice includes: spatial recall only (3 trials at size 2), symmetry only (15 trials), combined (3 trials at size 2)
- Main test: 12 trials total with set sizes [2,3,4,5] × 3 repetitions in randomized order
- Symmetry problems use 8×8 grids loaded from images in img/ directory
- Spatial recall uses 4×4 grid with red squares that flash for 650ms each
- Custom mouse-clickable 4×4 grid for recall with Clear/Del/Empty/Done buttons
- Real-time accuracy display shown in test phase (top right corner)
- Trial counter shows current trial / total trials during test phase
- Supports LSL markers for electrophysiological recording integration
- Supports online upload via InitializeUpload() and UploadFile()
- Uses HTML-lite formatted text with adaptive textboxes for instructions
- Includes 7 translations (en, es, de, pt, fr, nl, it) via JSON translation system
- Practice can be repeated once if symmetry threshold not met (allowsecondchance=1)
- Creates HTML report summarizing performance metrics and set size analysis
Key Parameters
| feedbacktimeout | Duration in milliseconds to display feedback after each trial (default: 1500) |
| distractfile | CSV file containing symmetry images (format: imagefile,answer,correctness) (default: distraction.csv) |
| batterythreshold | Minimum accuracy (0.0-1.0) required on symmetry problems to proceed to main test. Typically 0.85 (85%) (default: 0.85) |
| batteryFeedback | Whether to show feedback during test battery (1=yes, 0=no) (default: 1) |
| distracttimeoutminimum | Minimum timeout in milliseconds for symmetry problems during test battery (default: 1000) |
| distracttimeoutmultiplier | Multiplier for standard deviation when calculating symmetry timeout: timeout = mean + (multiplier × SD). Following Unsworth et al. (2005) who used 2.5*SD (default: 2.5) |
| requirethresholdprebattery | Require meeting accuracy threshold before starting test battery (1=yes, 0=no) (default: 1) |
| allowsecondchance | Allow a second practice attempt if first practice fails to meet threshold (1=yes, 0=no) (default: 1) |
| responsemode | Response collection mode (currently only 'none' is supported, using custom mouse grid) (default: none) |
| testreps | Number of repetitions for each set size in the test battery (e.g., 3 means each set size appears 3 times) (default: 3) |
| testminsize | Minimum set size (number of squares to recall) in the test battery. Must be at least 2 (default: 2) |
| testmaxsize | Maximum set size (number of squares to recall) in the test battery. Cannot exceed 16 (the memory grid size: 4 columns × 4 rows) (default: 5) |
Scoring & Interpretation
| Validation | validated |
| Psychometric data | Available |
| Normative data | Available |
Example Data Output (5 sample rows)
| subnum | trial | probtime | memtime | length | numstim | stim | resp | memcorr | time | distcorr | numcorrdist | totnumdist | runningcorrect | runningtotal |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| aaa | 1 | -1 | 1000 | 2 | 3 | 2|9 | 2|9 | 1 | -1 | -1 | 0 | 0 | 0 | 0 |
| aaa | 1 | -1 | 1000 | 3 | 6 | 3|12|7 | 3|12|7 | 1 | -1 | -1 | 0 | 0 | 0 | 0 |
| aaa | 1 | -1 | 0 | 0 | 1 | NA | 2585 | 1 | 1 | 1 | 1 | 1 | ||
| aaa | 1 | -1 | 0 | 0 | 1 | NA | 2329 | 1 | 2 | 2 | 3 | 3 | ||
| aaa | 1 | -1 | 0 | 0 | 1 | NA | 1684 | 1 | 1 | 1 | 4 | 4 |
References
Kane, M. J., Hambrick, D. Z., Tuholski, S. W., Wilhelm, O., Payne, T. W., & Engle, R. W. (2004). The generality of working memory capacity: A latent-variable approach to verbal and visuospatial memory span and reasoning. Journal of Experimental Psychology: General, 133(2), 189-217.
Unsworth, N., Redick, T. S., Heitz, R. P., Broadway, J. M., & Engle, R. W. (2009). Complex working memory span tasks and higher-order cognition: A latent-variable analysis of the relationship between processing and storage. Memory, 17(6), 635-654.
Authorship & License
| Original author | D.L. Hegarty & Dufflecoat Enterprises (2014) |
| PEBL implementation | S.T. Mueller |
| License | GPLv3 https://www.gnu.org/licenses/gpl-3.0.html |