Optimal Data Selection in the Reduced Array Selection Task (RAST)

The predictions of M. Oaksford and N. Chater's (1994) optimal data selection (ODS) model for the reduced array selection task (RAST) were tested in 4 experiments. Participants tested a hypothesis, ifp then q, by selecting cards showing q or not q instances. In Experiment 1, where selections were made from different sized stacks of q and not q cards, as P(q) increased, not q card selections rose, and q card selections fell, as predicted. Experiment 2 controlled for the possibility that stack height influenced responses; these results were also consistent with ODS. Experiment 3, which controlled further for this possibility, replicated Experiment 1. Experiment 4 addressed a final issue concerning the medium P(q) condition by concentrating on initial card selections; the results were again consistent with ODS. Although generally consistent with the ODS model, these experiments also suggest some interesting revisions.