Random generation performance: Some notes

"What I would like you to do is attempt to generate a random sequence of numbers between 1 and 10. Imagine, if you will, having these numbers written on pieces of paper placed in a hat. Shake the hat, draw out a piece of paper and read the number. Then put the paper back into the hat, shake it again, and draw another number out, and continue this process"

Instructions like those above might seem pretty strange. Why ask individuals to generate random sequences?

There are a number of answers one might give to the above question. Principally, however, it is because responses on the random generation task are thought to reveal information about important mental processes. That is, the way in which responses fall short of really random sequences provide potentially important clues to the characteristics of brain functioning.

Where do these ideas come from?

The random generation task has been around and used by psychologists for some time. However, a very important and influential paper was published by Baddeley (1966). Baddeley described a strong, orderly relationship between time available for making each random choice, and the quality of the sequence as a whole. Increasing response speed increased the amount of pattern which could be detected in responses, and this occurred in a consistent, quantitative fashion. These data were subsequently interpreted as evidence for a limited-capacity system responsible for random generation production (Baddeley, 1986; for more recent developments of these ideas, see Baddeley et al., 1998). This limited capacity system was identified as the central executive component within Baddeley's model of working memory.

Another early paper worth looking at, that describes random generation research, is by Wagenaar (1972). For an excellent, recent review of the random generation literature, consult Brugger (1997). This is a very good springboard from which to pursue resarch in the area. Examples of how random generation is used as a secondary task can be found in Logie, Gilhooly and Wynn (1994) and Abdi, Lemaire, and Fayol (1996). An investigation of random generation itself can be found in Towse (1998). Neuropsychological and brain imaging studies have also been reported - for examples of the latter, see Jahanshahi et al (1998) and other references given below

References and research pointers

Seminal early work and reviews

Baddeley, A. D. (1966). The capacity for generating information by randomization. Quarterly Journal of Experimental Psychology, 18, 119-129.

Baddeley, A. D. (1986). Working Memory. Oxford: Clarendon Press. (see chapter 10).

Brugger, P. (1997). Variables that influence the generation of random sequences: An update. Perceptual and Motor Skills, 84, 627-661.

Wagenaar, W. A. (1972). Generation of random sequences by human subjects: A critical survey of literature. Psychological Bulletin, 77(2), 65-72.

Experimental investigations

Baddeley, A. D., Emslie, H., Kolodny, J., & Duncan, J. (1998). Random generation and the executive control of working memory. Quarterly Journal of Experimental Psychology, 51A(4), 819-852.

Towse, J. N. (1998). On random generation and the central executive of working memory. British Journal of Psychology, 89, 77-101.

Towse, J. N., & Mclachlan, A. (1999). An exploration of random generation among children. British Journal of Developmental Psychology, 17(3), 363-380. (Abstract).

Towse, J. N., & Valentine, J. D. (1997). Random generation of numbers: A search for underlying processes. European Journal of Cognitive Psychology, 9(4), 381-400. (Abstract. There are on-line supplementary notes on findings from the Experiment I, and notes on Experiment II.)

Vandierendonck, A., De Vooght, G., & Van der Goten, K. (1998). Does random time interval generation interfere with working memory executive functions? European Journal of Cognitive Psychology, 10(4), 413-442.

Dual task studies

Lemaire, P., Abdi, H., &; Fayol, M. (1996). The role of working memory resources in simple cognitive arithmetic. European Journal of Cognitive Psychology, 8(1), 73-103.

Logie, R. H., Gilhooly, K. J., &; Wynn, V. (1994). Counting on working memory in arithmetic problem solving. Memory &; Cognition, 22(4), 395-410.

Neuropsychology and brain imaging

Brugger, P., Monsch, A. U., Salmon, D. P., & Butters, N. (1996). Random number generation in dementia of the Alzheimer type: A test of frontal executive functions. Neuropsychologia, 34(2), 97-103.

de Zubicaray, G. I., Williams, S. C. R., Wilson, S. J., Rose, S. E., Brammer, M. J., Bullmore, E. T., Simmons, A., Chalk, J. B., Semple, J., Brown, A. P., Smith, G. A., Ashton, R., & Doddrell, D. M. (1998). Prefrontal cortex involvement in selective letter generation: A functional magnetic resonance imaging study. Cortex, 34(3), 389-401.

Itagaki, F., Niwa, S., Itoh, K., & Momose, T. (1995). Random number generation and the frontal cortex. International Journal of Psychophysiology, 19, 79-80.

Jahanshahi, M., Profice, P., Brown, R. G., Ridding, M. C., Dirnberger, G., & Rothwell, J. C. (1998). The effects of transcranial magnetic stimulation over the dorsolateral prefrontal cortex on suppression of habitual counting during random number generation. Brain, 121, 1533-1544.

Knoch, D., Brugger, P., & Regard, M. (2005). Suppressing versus Releasing a Habit: Frequency-dependent Effects of Prefrontal Transcranial Magnetic Stimulation. Cerebral Cortex, 15, 885--887.

Robertson, C., Hazlewood, R., & Rawson, M. D. (1996). The effects of Parkinson's disease on the capacity to generate information randomly. Neuropsychologia, 34(11), 1069-1078.

Methods and analysis

Lopes, L. L., & Oden, G. C. (1987). Distinguishing between random and nonrandom events. Journal of Experimental Psychology: Learning, Memory and Cognition, 13(3), 392-400.

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. More info.

Subjective randomness

Falk, R., & Konold, C. (1997). Making sense of randomness: Implicit encoding as a basis for judgement. Psychological Review, 104(2), 301-318.

Rapoport, A., & Budescu, D. V. (1997). Randomization in individual choice behavior. Psychological Review, 104(3), 603-617.

Have I missed something important here? Suggestions for updates Let me know by email with j dot towse at lancs dot ac dot uk