Error, falsification and scientific inference: An experimental investigation

This paper reports the results of four experiments designed to test the methodological falsificationist's assumption that replication is sufficient to prevent the possibility of error from being used to immunize hypotheses against disconfirmation. The first three experiments compare the performance of subjects on tasks that simulate scientific reasoning under two conditions: (1) where there is a 0-20% possibility of error in experimental results, but no actual error; and (2) a control condition.

All experiments used Wason's 2-4-6 task, in which subjects propose triples and are told whether each corresponds to a rule. In Experiment 1, subjects in the possible-error condition proposed significantly more triples than control subjects. Experiment 2 added colour and letter dimensions to the 2-4-6 task; possible-error subjects proposed significantly more triples and replicated the same triple more often than control subjects. Experiment 3 made replication more difficult by limiting the number of experiments subjects could perform and by altering the rule to make the results of the current trial dependent on previous ones. Control subjects solved this problem significantly more often than possible-error subjects.

Experiment 4 was run in a manner very similar to Experiment 1, except that an actual 20% error condition was added. Subjects in this condition solved the rule significantly less often than subjects in other conditions, and also took more time and replicated more often. Implications of these results for the methodological falsificationist's position are discussed.