PEBL Hub — IRB Fact Sheet — 2026-08-23
Clock Test
Category:Attention
Duration:~2 minutes
Parameters:4 configurable parameters available
Version:1.0
Input:Keyboard
Description
PEBL Clock Test. An implementation of the Mackworth Clock Test. A sustained visual attention task--Watch for a clock to skip a beat.
A sustained visual attention vigilance task. Participants watch a red target move around a circular clock face like a second hand, advancing one position every second. Occasionally (with probability pskip, default 40%), the clock 'skips a beat' by advancing two positions instead of one. Participants must press the spacebar when they detect a skip. The task measures vigilance and sustained attention by tracking hits (correct detections), false alarms (responses to normal ticks), and response times over an extended period (default 60 trials).
Key Parameters
| pskip | Probability that any trial will be a 'skip' trial (default: 0.4) |
| radius | Radius of clock circle, in pixels. (default: 240) |
| size | Radius of target dots, in pixels (default: 9) |
| trials | Number of (1-second) trials to test. (default: 60) |
| responsemode | Response method: spacebar (keyboard), leftclick (click anywhere), touchscreen (tap anywhere) (default: spacebar) |
References
Mackworth, N. H. (1948). Mackworth Clock Test. The Quarterly Journal of Experimental Psychology.
Shackel, B. (1999). How I broke the Mackworth clock test (and what I learned). In Hanson, M., Lovesey, E. J., and Robertson, S. A. Contemporary Ergonomics 1999. Taylor & Francis. (pp. 193-197)
Lichstein, K. L., Riedel, B. W., & Richman, S. L. (2000). The Mackworth clock test: A computerized version (statistical data included). The Journal of Psychology. http://www.encyclopedia.com/doc/1G1-62024427.html Gets x,y coordinates based on 1:60 minutes.