PEBL Hub — IRB Fact Sheet — 2026-08-23
Dot Numerosity Judgment Task
Perception
Decision Making
Category:Perception
Duration:~8 minutes
Parameters:22 configurable parameters available
Version:1.0
Input:Keyboard
Description
A perceptual numerosity judgment task using interleaved staircase procedures to estimate thresholds.
Participants view two groups of dots displayed briefly on screen and judge which group contains more dots. The task uses simultaneous interleaved staircase procedures to adaptively adjust difficulty, converging on the participant's discrimination threshold.
Measures: Numerosity discrimination, perceptual judgment
Key Parameters
| numblocks | Number of blocks of trials to test (default: 4) |
| repsperblock | Repetitions of each base level per block (default: 25) |
| resetthresh | Should the thresholds be reset to the median of the previous block threshold between each block? (default: 1) |
| prestime | Time in ms to present block before it disappears. use -1 to prevent it from disappearing. (default: -1) |
| base1 | Dot comparison set size 1 (default: 6) |
| base2 | Dot comparison set size 2 (default: 20) |
| base3 | Dot comparison set size 3 (default: 50) |
| base4 | Dot comparison set size 3 (default: 100) |
| thresh1 | Starting threshold for set 1 (default: 4) |
| thresh2 | Starting threshold for set 2 (default: 4) |
| thresh3 | Starting threshold for set 3 (default: 4) |
| thresh4 | Starting threshold for set 4 (default: 4) |
| errorAdj | How much to adjust the dot threshold after an error (+1) (default: 1) |
| correctAdj | How much to adjust the dot threshold after correct. (default: -0.25) |
| fieldsize | Size in pixels of field square (default: 450) |
| border | Size in pixels of 'border', around field (default: 100) |
| dotcolor | Color of dots (default: red) |
| dotfilled | Whether dots should be filled (default: 1) |
| dotradius | Radius of dots in pixels (default: 10) |
| useAudioFeedback | Whether audio feedback should be given. (default: 1) |
| responsetype | currently, changing this has no effect. (default: keyboard) |
| responsemode | Response method: auto (platform-aware), keyboardShift (L/R shift), keyboardSafe (Z/slash for web), arrowLR (left/right arrows), mousetarget (click targets), touchtarget (tap targets), mousebutton (L/R mouse buttons), userselect (custom key) (default: auto) |
Scoring & Interpretation
Lower threshold values indicate better numerosity discrimination. Thresholds are estimated via staircase convergence across multiple interleaved procedures with different standard values.
Example Data Output (5 sample rows)
| subnum | block | trial | practice | standard | thresh | side | corr | abstime | rt |
|---|---|---|---|---|---|---|---|---|---|
| subnum | block | trial | practice | standard | thresh | side | corr | abstime | rt |
| 111 | 1 | 1 | 1 | 50 | 4 | 1 | 1 | 3191 | 2739 |
| 111 | 1 | 2 | 1 | 6 | 4 | 1 | 1 | 6543 | 854 |
| 111 | 1 | 3 | 1 | 100 | 4 | -1 | 0 | 8004 | 737 |
| 111 | 1 | 4 | 1 | 6 | 3.75 | -1 | 1 | 9359 | 857 |
References
Mueller, S. T. (2011). The PEBL Dot Judgment Task. Computer software retrieved from http://pebl.sf.net/battery.html