Predicting others through simulation or by theory? A method to decide

A method is presented for deciding whether correct predictions about other people are based on simulation or theory use. The differentiating power of this method was assessed with cognitive estimation biases (e.g. estimating the area of Brazil) in two variations. Experiments 1 and 2 operated with th e influence of response scales of different length. Experiment 3 used the d ifference between free estimates that tended to be far off the true value a nd estimates constrained by an appropriate response scale, where estimates became greatly more realistic. The critical question is how well observer s ubjects can predict these target biases under two different presentation co nditions. Response scale biases (Experiments 1 and 2) were more strongly pr edicted when observer subjects were presented with the two scales juxtapose d, than when responses for each scale were given independently. This speaks for the use of a theory, since simulation should, if there is any differen ce at all, be made more difficult by the juxtaposition of conditions. The d ifference between free and constrained estimations (Experiment 3) was more strongly predicted under independent than under juxtaposed presentation. Th is speaks for the use of simulation since use of a theory should, if anythi ng, be helped by juxtaposition of problems since it helps highlight the the oretically relevant factor. Results are discussed in view of recent proposa ls about when simulation is likely to be used, i.e. for belief fixation but not action prediction (Stich and Nichols, 1995b), for content fixation (He al, 1996a), and for rational effects only (Heal, 1996b).