Prediction and diagnosis: Task variable revealed
RICKARD NILSSON, MATS BJÖRKMAN · Scandinavian Journal of Psychology · 1982
The authors' work on demonstrating fundamental differences between predictive learning and diagnostic learning lead incidentally to the discovery of a critical task variable operating in diagnostic tasks. In our experiments these tasks consist of random sampling with replacement of cues from two cue‐generators. The subject has to infer from which cue‐generator the cue was drawn. Two different sampling procedures can be distinguished. Under forced sampling the predetermined probabilities of the occurrence of each cue agree exactly with the relative frequencies within each block of trials. Under free sampling there are no with in‐block restrictions on the sampling, which results in sampling fluctuations from block to block. It was demonstrated that this difference in sampling is a critical task variable. Free sampling results in a higher frequency of long sequences of confirming trials, that is, trials in which feedback indicates the optimal rule. The excess of long sequences of confirming trials under free sampling makes this kind of sampling a better condition for efficient learning than forced sampling. If one believes (as the authors do) that “nature” does not apply forced sampling the results indicate that the “natural” way of sampling is also the most favorable for learning diagnostic tasks.