PEBL Hub — IRB Fact Sheet — 2026-08-23
Random Generation Task
Executive Function
Processing Speed
Category:Executive Function
Duration:~10 minutes
Parameters:5 configurable parameters available
Version:1.0
Description
A task measuring executive function where participants attempt to generate random sequences of digits in time with an auditory/visual pacing signal.
Participants press number keys (0-9) one at a time, paced by a beep and flashing circle. The goal is to produce a sequence as random as possible. Multiple randomness metrics are computed including RNG score, redundancy, adjacency, turning points, and repetition gaps. These metrics quantify how well participants suppress habitual patterns and maintain random output.
Measures: Executive function, inhibition, working memory, random generation ability
Key Parameters
| numtrials | Number of total trials to use. (default: 162) |
| practicetrials | Number of practice trials (default: 15) |
| isi | ISI in ms for the beeps (default: 800) |
| usebeep | Whether to use a beep to guide responses (default: 1) |
| useflash | Whether to use a flash to guide responses (default: 1) |
Scoring & Interpretation
Key metrics from the summary report: RNG (Evans, 1978): 0=perfectly random, 1=completely predictable. Redundancy: percentage deviation from uniform distribution. NSQ (Guttmann's Null-Score Quotient): percentage of unused digit pairs. Adjacency: percentage of ascending/descending consecutive pairs. TPI (Turning Point Index): 100=expected number of direction changes. Repetition Gap: mean distance between repeated digits.
References
Towse, J. N., & Neil, D. (1998). Analyzing human random generation behavior: A review of methods used and a computer program for describing performance. Behavior Research Methods, Instruments, & Computers, 30(4), 583-591.
Mueller, S. T. (2011). The PEBL Random Generation Task. Computer software retrieved from http://pebl.sf.net/battery.html